Polysaccharides - structural diversity and functional diversity

Polysaccharides structural diversity and functional diversity

The first edition was published as Polysaccharides: Structural Diversity and Functional Versatility, edited by Severian Dumitriu (Marcel Dekker, Inc., 1998) Although great care has been taken to provide accurate and current information, neither the author(s) nor the publisher, nor anyone else associated with this publication, shall be liable for any loss, damage, or liability directly or indirectly caused or alleged to be caused by this book The material contained herein is not intended to provide specific advice or recommendations for any specific situation Trademark notice: Product or corporate names may be trademarks or registered trademarks and are used only for identification and explanation without intent to infringe Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 0-8247-5480-8 This book is printed on acid-free paper Headquarters Marcel Dekker 270 Madison Avenue, New York, NY 10016, U.S.A tel: 212-696-9000; fax: 212-685-4540 Distribution and Customer Service Marcel Dekker Cimarron Road, Monticello, New York 12701, U.S.A tel: 800-228-1160; fax: 845-796-1772 World Wide Web http://www.dekker.com The publisher offers discounts on this book when ordered in bulk quantities For more information, write to Special Sales/Professional Marketing at the headquarters address above Copyright n 2005 by Marcel Dekker All Rights Reserved Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval system, without permission in writing from the publisher Current printing (last digit): 10 PRINTED IN THE UNITED STATES OF AMERICA Copyright 2005 by Marcel Dekker Foreword Polysaccharides as natural polymers are by far the most abundant renewable resource on the earth with an annual formation rate surpassing the world production rate of synthetic polymers by some orders of magnitude In contrast to petroleum-based synthetic polymers, plant polysaccharides are sustainable materials synthesized by the sun’s energy and fully biodegradable in the original state Thus, with decreasing supply of oil resources polysaccharides, including cellulose, starch, chitin, and hemicelluloses, are expected to play an increasingly important role in industrial use Polysaccharides are designed by nature to carry out various specific functions Examples comprise structural polymers such as cellulose and chitin, storage polysaccharides such as starch and glycogen, and gel forming mono- and copolymers such as mucopolysaccharides (glycosaminoglycans), agar, and pectins Generally, polysaccharides are highly functional polymers with magnificent structural diversity and functional versatility Their structural and functional properties are often superior to synthetic materials as demonstrated, for instance, by the cellulose based cell wall architecture of plants or the function of hyaluronic acid in the human body It has been a true challenge to present state-of-the-art polysaccharide research from different aspects regarding the macromolecular variety, function and structure in just one volume In this book well-known and recognized authors describe the current state of research in their specific fields of expertise in which many of them have been active for decades With regard to cellulose and starch as the most abundant polysaccharides, structure, chemical modification, physical chemistry, and industrial aspects are being discussed It is further demonstrated that cellulosic biomass conversion technology permits large scale sustainable production of basic chemicals and derived products The focus of other chapters are bacterial polysaccharides, hemicelluloses, gums, chitin, chitosan, hyaluronan, alginates, proteoglycans, glycolipides, and heparan sulfate-like polysaccharides Some chapters deal with medical and pharmaceutical aspects including medical foods, anticoagulant properties and the role of polysaccharides in tissue engineering Furthermore, methodical aspects, including characterization by X-ray scattering, spectroscopic methods, light scattering, and rheology are discussed In summary, the comprehensive, improved, and expanded second edition of ‘‘Polysaccharides’’ reflects the current state of knowledge of nearly the entire spectrum of polysaccharides with emphasis on structures, methods of structural analysis, functions and properties, novel routes of modification, and novel application fields With each chapter, the reader will find references for a deeper insight into a specific field Thus, this book is a very useful tool for scientists of both academia and industry interested in the fundamental principles of polysaccharide functions and modifications on one hand and novel applications on the other Having been involved in similar work mainly with industry-related issues of cellulose research for many years, I would like to stress that the presented state of knowledge, as sophisticated as it might seem to be, should not be understood as the final stage, but as an invitation to add new knowledge to this field and to explore additional applications of polysaccharides I would be delighted, if this monograph challenged and encouraged scientists to deal with polysaccharides as fascinating polymers with a bright future Hans-Peter-Fink Fraunhofer-Institute for Applied Polymer Research Potsdam-Golm, Germany iii Copyright 2005 by Marcel Dekker Preface Polysaccharides are the macromolecules that belong to the means components of life Together with nucleic acids and proteins, the polysaccharides determine the functionality and specificity of the species Polysaccharides have received little such promotion even though they are widely distributed throughout nature and have highly organized structure There are important molecules involved throughout the body in signal transduction and cell adhesion Polysaccharides can be broadly classified into three groups based on their functions, which are closely related to their occurrence in nature: structural, storage, and gel forming The first compounds used at the industrial level were the polysaccharides This work provides the most complete summary now available of the present knowledge of polysaccharide chemistry This book discusses eleven fundamental aspects of polysaccharides: Progress in structural characterization The structural analysis may offer the most fundamental knowledge to understand the functions of polysaccharides, but the diversity and irregularity of polysaccharide chains make the structural analysis a formidable task The conformational analysis involves two aspects: (a) the characterization of a single chain conformation and (b) the analysis of the chain assembly of polysaccharides A remarkable progress has been achieved in recent years with high-resolution, solution- and solid-state-1H- and 13C-NMR including cross-polarization-magic-angle-spinning and two-dimensional techniques Specific electron microscopy techniques can visualize single polysaccharide molecules and can yield reliable information on their contour length distribution, persistence length and conformational aspects Some recent progress reports on computational methods for simulations and calculations associated with structure elucidation of polysaccharides have demonstrated that these methods can contribute to a ‘‘decision’’ on the actual conformational properties of oligosaccharides and linear polysaccharides Conformation and dynamic aspects of polysaccharide gels The most important aspect of characterization of polysaccharide gels seems to clarify their backbone dynamics together with conformations as viewed from their highly heterogeneous nature Backbone dynamics of polysaccharide gel network can be characterized by means of simple comparative high-resolution 13C NMR measurements by cross-polarization-magic angle spinning (CP-MAS) and dipolar decoupled-magic angle spinning (DD-MAS) techniques Rheological behavior of polysaccharides in aqueous systems Rheology provides precious tools to explore and understand the properties of polysaccharides in aqueous systems The rheological behavior of polysaccharides systems manifests the underlying structure of the systems In the simplest case, that of polysaccharides solution, viscosity is directly related to fundamental molecular properties (molecular conformations, molecular weight and molecular weight distribution, intramolecular and intermolecular interactions) In the case of more structured polymer systems, gels, for example, their viscoelastic properties are related to supramolecular organization The main types of polysaccharide systems that are encountered in the applications can be distributed schematically in three classes: solutions, gels, and polysaccharide/ polysaccharide (or polysaccharide/protein) mixtures in aqueous media Biosynthesis, structure, and physical properties of bacterial polysaccharides (exopolysaccharides) This part presents the mechanisms of biosynthesis of bacterial polysaccharides and provides some information on the engineering of polysaccharides that will allow in the near future the production of a polysaccharide with a choice chemical structure having a set of predictable physical properties This part covers also pertinent areas such as: bacterial and fungal polysaccharides, cell-wall polysaccharides, production of microbial polysaccharides, industrial gums, and microbial exopolysaccharides of practical importance Copyright 2005 by Marcel Dekker vi Preface The bacterial polysaccharides are described as: production and synthesis, composition and structure, physical properties, degradation by polysaccharases and polysaccharide lyases, polysaccharides common to prokaryotes and eukaryotes, biological properties and applications and commercial products One chapter is dedicated to the presentation of the order-disorder conformational transition of xanthan gum Hemicelluloses may function both as framework and matrix substances or reserve substances in seeds, where they form independent wall layers which are mobilized when the seed germinates In both hardwood and softwood, hemicelluloses fraction in lignified cell walls represents the matrix substance This important part of the polysaccharides chemistry is presented in three chapters: Hemicelluloses: Structure and properties; Chemical modification of hemicelluloses and gums; Role of acetyl substitution in hardwood xylan In this edition a particular emphasis is placed on the presentation of the ionic polysaccharides (polyanion and polycation) in the following chapters: Alginate—A polysaccharide of industrial interest and diverse biological functions; Characterization and properties of hyaluronic acid (hyaluronan); Structure – property relationship in chitosans; Chitosan as a delivery system for transmucosal administration of drugs; Pharmaceutical applications of chitosan; Macromolecular complexes of chitosan Cellulose and starch are the two polysaccharides which constitute the majority of the polysaccharide production They are presented in four chapters: Chemical functionalization of cellulose; The physical chemistry of starch; Starch: commercial sources and derived products; New development in cellulose technology The polysaccharides of a major importance in medicine and biology are extensively discussed in nine chapters: Polysialic acid: structure and properties; Brain proteoglycans; Crystal structures of glycolipids; Synthetic and natural polysaccharides with anticoagulant properties; Structural elucidation of heparan sulfate-like polysaccharides using miniaturized LC/MS; Enzymatic synthesis of heparan sulfate; Synthetic and natural polysaccharides having biological activities; Polysaccharide-based hydrogels in tissue engineering and Medical foods and fructooligosaccharides Polysialic acids form a structurally unique group of linear carbohydrate chains with a degree of polymerization up to 200 sialyl residue Polysialic acids chains are covalently attached to membrane glycoconjugates on cells that range in evolutionary diversity from bacteria to human brains Proteoglycans, a group of glycoproteins that are invested with covalently bound glycosaminoglycan chains, are one of the important classes of molecules in brain development and maturation The glycosaminoglycan chains that define proteoglycans are of four major classes: heparan sulfate; chondroitin sulfate, dermatan sulfate and keratan sulfate The glycolipids play roles as the structural holder of membrane proteins suspended in bilayer or bicontinuous cubic phases and as the key code of the intercellular communication or immune system Anticoagulant polysaccharides as heparin, heparan sulfate and nonheparin glycosaminoglycans (dermatan sulfate, chondroitin sulfates, acharan sulfate, carrageenas, sulfated fucans, sulfated galactan and nonheparin glycosaminoglycans from microbial sources) have been of interest to the medical profession Renewable resources Cellulosic biomass includes agricultural (e.g., corn stover and sugarcane bagase) and forestry (e.g., sawdust, thin-nings, and mill wastes) residues, portions of municipal solid waste (e.g., waste paper) and herbaceous (e.g., switch-grass) and woody (e.g., poplar trees) corps They are appropriate materials used as renewable resources for the production of building blocks for various industrial chemicals and engineering plastics polysaccharides The chapters ‘‘Bioethanol production from lignocellulosic material’’, and Cellulosic biomass-derived products, describe and evaluate the process for ethanol fuel production The raw material, hydrolysis, and fermentation are described in detail as well as the different possibilities to perform these process steps in various process designs The chapter ‘‘Hydrolysis of cellulose and hemicellulose’’ presents a comprehensive overview of the technology and economic status for cellulose and hemicellulose hydrolysis describes the important structural features of cellulosic materials, applications, process steps, and stoichiometry for hydrolysis reactions The chapter then examines biomass structural characteristics that influence cellulose hydrolysis by enzymes, types of cellulose hydrolysis processes, experimental results for enzymatic conversion of cellulose, and summarizes some of the factors influencing hydrolysis kinetics 10 New applications of polysaccharides This section provides a selection of some new developmental products and some recent applications, which might become of commercial interest in the near future The polysaccharides are utilized as gallants, thickeners, film formers, fillers, and delivery systems in pharmaceutical and cosmetic applications Immobilization The use of ionic polysaccharides for the immobilization (enzymes, cells and other biocatalysts for biotechnological production) Ligand systems Chitin, chitosan and other functional polysaccharides have also been widely used for the preparation of metal chelators Industrial application ranges from waste water treatment, ion exchange resins, and precious metal recovery Separatory systems Cellulose and chitosan derivatives are dominating the membrane market due to their favorable stability and their selectivity in gas- and liquid-phase separations Biosurfactants Numerous microorganisms (candida lipolytica, Acetinobacter calcoaceticus) produce extracellular glycoconjugates with pronounced capabilities to modify interfacial and surface conditions Cellulose derivative composites for electro-optical applications These studies present an optical cell formed by a transparent solid matrix of mixed esters of cellulose with micrometer-sized pores filled with a nemantic liquid crystal Copyright 2005 by Marcel Dekker Preface vii 11 Incorporation of the polysaccharides in the synthetic matrix offers on one hand the possibility to obtain a broader application range of the usual polymers and, on the other hand, ways to optimize and control some properties and produce new materials with unexpected performance at low cost The treatise is truly international with authors now residing in Austria, Brazil, Canada, Denmark, Egypt, Finland, France, Germany, Greece, Japan, The Netherlands, Norway, Portugal, Romania, Sweden, United Kingdom, and the United States The editor is grateful to all the collaborators for their precious contributions Severian Dumitriu Copyright 2005 by Marcel Dekker Contents Foreword Hans-Peter-Fink Preface Contributors Progress in Structural Characterization of Functional Polysaccharides Kanji Kajiwara and Takeaki Miyamoto Conformations, Structures, and Morphologies of Celluloses Serge Pe´rez and Karim Mazeau Hydrogen Bonds in Cellulose and Cellulose Derivatives Tetsuo Kondo X-ray Diffraction Study of Polysaccharides Toshifumi Yui and Kozo Ogawa Recent Developments in Spectroscopic and Chemical Characterization of Cellulose Rajai H Atalla and Akira Isogai Two-Dimensional Fourier Transform Infrared Spectroscopy Applied to Cellulose and Paper ˚ Lennart Salme´n, Margaretha Akerholm, and Barbara Hinterstoisser Light Scattering from Polysaccharides Walther Burchard Advances in Characterization of Polysaccharides in Aqueous Solution and Gel State M Rinaudo Conformational and Dynamics Aspects of Polysaccharide Gels by High-Resolution Solid-State NMR Hazime Saitoˆ 10 Correlating Structural and Functional Properties of Lignocellulosics and Paper by Fluorescence Spectroscopy and Chemometrics Emmanouil S Avgerinos, Evaggeli Billa, and Emmanuel G Koukios Copyright 2005 by Marcel Dekker x Contents 11 Computer Modeling of Polysaccharide–Polysaccharide Interactions Francois R Taravel, Karim Mazeau, and Igor Tvarosˇka ß 12 Interactions Between Polysaccharides and Polypeptides Delphine Magnin and Severian Dumitriu 13 Rheological Behavior of Polysaccharides Aqueous Systems Jacques Lefebvre and Jean-Louis Doublier 14 Stability and Degradation of Polysaccharides Valdir Soldi 15 Biosynthesis, Structure, and Physical Properties of Some Bacterial Polysaccharides Roberto Geremia and Marguerite Rinaudo 16 Microbial Exopolysaccharides I W Sutherland 17 Order–Disorder Conformational Transition of Xanthan Gum Christer Viebke 18 Hemicelluloses: Structure and Properties Iuliana Spiridon and Valentin I Popa 19 Chemical Modification of Hemicelluloses and Gums Margaretha Soăderqvist Lindblad and Ann-Christine Albertsson 20 Role of Acetyl Substitution in Hardwood Xylan Maria Groăndahl and Paul Gatenholm 21 Alginate—A Polysaccharide of Industrial Interest and Diverse Biological Functions Wael Sabra and Wolf-Dieter Deckwer 22 Characterization and Properties of Hyaluronic Acid (Hyaluronan) Michel Milas and Marguerite Rinaudo 23 Chemical Functionalization of Cellulose Thomas Heinze 24 The Physical Chemistry of Starch R Parker and S G Ring 25 Starch: Commercial Sources and Derived Products Charles J Knill and John F Kennedy 26 Structure–Property Relationship in Chitosans Kjell M Va˚rum and Olav Smidsrød 27 Chitosan as a Delivery System for the Transmucosal Administration of Drugs Lisbeth Illum and Stanley (Bob) S Davis 28 Pharmaceutical Applications of Chitosan and Derivatives M Thanou and H E Junginger 29 Macromolecular Complexes of Chitosan Naoji Kubota and Kei Shimoda 30 Polysialic Acid: Structure and Properties Tadeusz Janas and Teresa Janas Copyright 2005 by Marcel Dekker Contents 31 Brain Proteoglycans Russell T Matthews and Susan Hockfield 32 Crystal Structures of Glycolipids Yutaka Abe and Kazuaki Harata 33 Synthetic and Natural Polysaccharides with Anticoagulant Properties Fuming Zhang, Patrick G Yoder, and Robert J Linhardt 34 Structural Elucidation of Heparan Sulfate-Like Polysaccharides Using Miniaturized LC/MS Balagurunathan Kuberan, Miroslaw Lech, and Robert D Rosenberg 35 Enzymatic Synthesis of Heparan Sulfate Balagurunathan Kuberan, David L Beeler, and Robert D Rosenberg 36 Polysaccharide-Based Hydrogels in Tissue Engineering Hyunjoon Kong and David J Mooney 37 Synthetic and Natural Polysaccharides Having Specific Biological Activities Takashi Yoshida 38 Medical Foods and Fructooligosaccharides Bryan W Wolf, JoMay Chow, and Keith A Garleb 39 Immobilization of Cells in Polysaccharide Gels Yunyu Yi, Ronald J Neufeld, and Denis Poncelet 40 Hydrothermal Degradation and Fractionation of Saccharides and Polysaccharides Ortwin Bobleter 41 Cellulosic Biomass-Derived Products Charles J Knill and John F Kennedy 42 Bioethanol Production from Lignocellulosic Material Lisbeth Olsson, Henning Jørgensen, Kristian B R Krogh, and Christophe Roca 43 Hydrolysis of Cellulose and Hemicellulose Charles E Wyman, Stephen R Decker, Michael E Himmel, John W Brady, Catherine E Skopec, and Liisa Viikari 44 New Development in Cellulose Technology Bruno Lo ănnberg 45 Polysaccharide Surfactants: Structure, Synthesis, and Surface-Active Properties Roger E Marchant, Eric H Anderson, and Junmin Zhu 46 Structures and Functionalities of Membranes from Polysaccharide Derivatives Tadashi Uragami 47 Electro-optical Properties of Cellulose Derivative Composites J L Figueirinhas, P L Almeida, and M H Godinho 48 Blends and Composites Based on Cellulose Materials Georgeta Cazacu and Valentin I Popa 49 Preparation and Properties of Cellulosic Bicomponent Fibers Richard D Gilbert and John F Kadla Copyright 2005 by Marcel Dekker xi Contributors Yutaka Abe Process Development Research Center, Lion Corporation, Tokyo, Japan ˚ Margaretha Akerholm STFI (Swedish Pulp and Paper Research Institute), Stockholm, Sweden Ann-Christine Albertsson Royal Institute of Technology, Stockholm, Sweden P L Almeida EST/IPS, Setubal, Portugal and FCT/UNL, Caparica, Portugal ´ Case Western Reserve University, Cleveland, Ohio, U.S.A Eric H Anderson Rajai H Atalla USDA Forest Service and University of Wisconsin, Madison, Wisconsin, U.S.A Emmanouil S Avgerinos National Technical University of Athens, Athens, Greece David L Beeler Massachusetts Institute of Technology, Cambridge, Massachusetts, U.S.A and Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, U.S.A Evaggeli Billa National Technical University of Athens, Athens, Greece Ortwin Bobleter University of Innsbruck, Innsbruck, Austria John W Brady Cornell University, Ithaca, New York, U.S.A Walther Burchard Institute of Macromolecular Chemistry, University of Freiburg, Germany Georgeta Cazacu ‘‘Petru Poni’’ Institute of Macromolecular Chemistry, Iasi, Romania JoMay Chow Abbott Laboratories, Columbus, Ohio, U.S.A Stanley (Bob) S Davis University of Nottingham, Nottingham, United Kingdom Copyright 2005 by Marcel Dekker xiv Contributors Stephen R Decker National Renewable Energy Laboratory, Golden, Colorado, U.S.A Biochemical Engineering, GBF–National Research Center for Biotechnology, Braunschweig, Wolf-Dieter Deckwer Germany ´ INRA-Laboratoire de Physico-Chimie des Macromolecules, Nantes, France Jean-Louis Doublier Severian Dumitriu Sherbrooke University, Sherbrooke, Quebec, Canada J L Figueirinhas CFMC/UL, Lisbon, Portugal Keith A Garleb Abbott Laboratories, Columbus, Ohio, U.S.A Paul Gatenholm Biopolymer Technology, Department of Materials and Surface Chemistry, Chalmers University of Technology, Goteborg, Sweden ă Roberto Geremia Laboratoire dAdaptation et de Pathogenie des Microorganismes, Joseph Fourier University, Grenoble, France Richard D Gilbert North Carolina State University, Raleigh, North Carolina, U.S.A FCT/UNL, Caparica, Portugal M H Godinho ă Maria Grondahl Biopolymer Technology, Department of Materials and Surface Chemistry, Chalmers University of Technology, Goteborg, Sweden ă Kazuaki Harata Biological Information Research Center, National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan Thomas Heinze Center of Excellence for Polysaccharide Research at the Friedrich Schiller University of Jena, Jena, Germany Michael E Himmel National Renewable Energy Laboratory, Golden, Colorado, U.S.A Barbara Hinterstoisser Susan Hockfield Yale University School of Medicine, New Haven, Connecticut, U.S.A IDentity, Nottingham, United Kingdom Lisbeth Illum Akira Isogai BOKU-University of Natural Resources and Applied Life Sciences, Vienna, Austria Graduate School of Agricultural and Life Science, University of Tokyo, Tokyo, Japan Tadeusz Janas Teresa Janas University of Colorado, Boulder, Colorado, U.S.A ´ University of Colorado, Boulder, Colorado, U.S.A and University of Zielona, Gora, Poland Henning Jørgensen Center for Microbial Biotechnology BioCentrum-DTU, kgs Lyngby, Denmark H E Junginger Leiden University, Leiden, The Netherlands John F Kadla North Carolina State University, Raleigh, North Carolina, U.S.A Kanji Kajiwara Copyright 2005 by Marcel Dekker Otsuma Women’s University, Chiyoda-ku, Tokyo, Japan 1174 polyethylene blended with thermotropic hydroxyethyl cellulose acetate J Appl Polym Sci 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carboxymethylcellulose (CMC): synthesis and ion effect Polym Int 2001, 50 (12), 1370–1374 49 Preparation and Properties of Cellulosic Bicomponent Fibers Richard D Gilbert and John F Kadla North Carolina State University, Raleigh, North Carolina, U.S.A I INTRODUCTION The majority of commercial polymers are derived from petroleum, which is becoming increasingly scarce These products are also largely unrecyclable Cellulose and other biopolymers may provide an abundant and environmentally friendly alternative to synthetic polymers Cellulose constitutes the most abundant, renewable polymer resource It has been estimated [1] that the yearly photosynthesis of biomass is 170 billion tons, 40% of which consists of polysaccharides, mainly cellulose and starch Today, with the availability of an enormous variety of synthetic polymers, cellulose and its derivatives are somewhat overshadowed Nevertheless, cellulose occupies a unique place in the annals of high polymers It was one of the first polymers studied starting with Anselm Payen’s investigations [2] ‘‘Many of the basic principles were worked out in the course of cellulose investigations’’ [3] Payen first recognized cellulose as a definitive substance and coined the name cellulose Today it is still widely investigated Synthesis of cellulose derivatives and regeneration of cellulose, along with the physical chemistry of cellulosic solutions, including those that are mesomorphic, constitute areas of active research The use of cellulose and its derivatives in a diverse array of applications, such as fibers, films, plastics, coatings, suspension agents, composites, and wood and paper products, continues to grow on a worldwide basis Relatively newer uses of cellulose and cellulose derivatives include cellulosic fibers and membranes for hemodialysis and hemafiltration, chiral isomer separations, calorie-free fat substitutes, absorbent nonwovens, stimuli-responsive materials, and the like [4–6] In 1838, Payen first proposed the elemental composition of cellulose to be C6H10O5 [2], classifying it as a carbohydrate A number of studies [7–10] have shown that cellulose is a chainlike extended linear macromolecule of Copyright 2005 by Marcel Dekker h-D-glucopyranose units linked by (1,4) glycosidic bonds in which the anhydroglucopyranose units exist in the lowest energy 4C1-chair conformation [11] The structure of cellulose suggests it can be considered a polysaccharide and a priori it would be expected to be readily soluble in polar solvents However, due to extensive intra- and intermolecular hydrogen bonding and its high degree of crystallinity (ca 60–80%) it is insoluble in polar solvents Interestingly, Haynes [12] points out that if cellulose was readily soluble ‘‘our vegetable-clad planet would be a very different place.’’ It should be noted that a cellulose molecule has a reducing end group, as the chemical linkage between the C1 carbon and the ring oxygen is a hemiacetal and allows the ring to open to generate an aldehyde The other end-group is a secondary alcohol and thus is commonly referred to as the nonreducing end group The reducing end group is responsible for the reducing properties of cellulose For example, cellulose has the ability to reduce copper from the cupric to the cuprous state and silver ions to the metal Phenylhydrazine, hydrazine, and compounds that react with carbonyl groups react with cellulose As shown in Fig 1, each anhydroglucopyranose, or structural unit of cellulose, has three hydroxyl groups, one primary and two secondary These groups undergo chemical reactions (e.g., esterification and etherification) typical of hydroxyl groups However, the situation is complicated by the microstructure of native celluloses (wood and cotton fiber, the major raw material sources for the preparation of cellulose derivatives), which have high degrees of crystallinity This limits the accessibility of the hydroxyl groups to reactants There is no difference between the intrinsic reactivities of cellulose hydroxyl groups and the hydroxyl groups of small molecules, but in the case of cellulose the crystallinity and solubility hinders the access of the hydroxyl 1180 Gilbert and Kadla Figure Constitutional formula of the cellulose molecule The h-D-glucopyranose units are in the 4C1-chair conformation with all substituents orientated equatorially groups to reagents The hydroxyl groups in the disordered regions react readily with various reactants; but the crystalline regions, due to their close packing and extensive interchain hydrogen bonding, are not readily accessible and, initially, reaction occurs mainly on the surface of the crystallites A detailed discussion of the effect of the morphology and structure of cellulose on its reactivity and on cellulose substitution reactions has been given by Krassig [1] Cellulose and other biopolymers have several advantages over synthetic materials These include low cost, low density, high toughness, reduced tool wear, carbon dioxide sequestration, and reduced dermal and respiratory irritation [13,14] In fact, the replacement of steel automotive parts with lightweight biomaterials can reduce the vehicle weight by as much as 80% [15] This translates into more efficient fuel consumption because less energy is required for motion Unfortunately, the processability of cellulose is inferior to that of most synthetic materials Consequently, cellulose must be chemically modified or combined with other materials in order to obtain usable products The following sections will examine some common techniques for modifying the properties of cellulose for use in bicomponent fiber applications II CELLULOSE DERIVATIVES Derivatives of cellulose constitute the most important area of cellulose modification from both a technological and commercial viewpoint From both a physical and chemical basis cellulose is a rather intractable material It cannot be converted into different shapes by injection molding or melt extrusion, as due to its high melting point cellulose thermally degrades prior to obtaining the ability to flow Similarly, it is not soluble in common organic solvents from which films, fibers, etc can be readily cast or spun Many cellulose derivatives (e.g., the acetates) are soluble in organic solvents and can be extruded into fibers or films and are sufficiently thermoplastic that they can be readily molded into a variety of shapes Therefore, cellulose derivatives make up a critical step in the production of bicomponent cellulosic materials At present there is one exception to the above situation Cellulose is readily soluble in N-methyl morpholine N-oxide (NMMO) and so-called lyocell fibers are being Copyright 2005 by Marcel Dekker spun from solutions of cellulose in this solvent However, NMMO, being an organic ether, readily forms explosive peroxides and must be properly stabilized before use The chemical and physical properties of cellulose derivatives are influenced by the type and nature of the substituents, the degree of substitution (DS), the distribution of substituents, the average molecular weight and molecular weight distribution The degree of substitution of a cellulose derivative is the average number of reacted hydroxyl groups per anhydroglucopyranose unit As each anhydroglucopyranose structural unit has three hydroxyl groups, the maximum DS is The chemical and physical properties of a derivative depend on the DS For example, cellulose triacetate (CTA, DS = 3) has a higher degree of crystallinity than secondary cellulose acetate (DS f 2.4) because of the greater structural uniformity of CTA CTA is soluble in nonpolar solvents but not in polar solvents The reverse is true for secondary cellulose acetate Secondary cellulose acetate is much more easily dyed than CTA At a DS of ca 1, cellulose acetate is water soluble That is, its crystallinity and intermolecular hydrogen bonding is sufficiently disrupted that the hydroxyl groups are accessible to water, and solvation of the cellulose molecule is possible Distribution of the substituents refers to the number and location of the substituents on a particular anhydroglucopyranose unit and to the number of substituents on the anhydroglucopyranose units constituting the cellulose molecule Of course, the location of the substituents on a particular anhydroglucopyranose unit depends on the relative reactivities of the C-2, C-3, and C-6 hydroxyl groups with a particular reagent In general, kinetically controlled reactions (e.g., SN2 type) preferentially and most rapidly occur at the C-2 OH and equilibrium reactions at the C-6 OH (In the following reaction schemes CELLOH is used as an abbreviation for cellulose.) O CELLO ỵ CH2 -CH2 CELLO ỵ RX ! ! The C-3 OH is always the least reactive regardless of the type of reaction However, in some cases, the preferred OH group depends on the reactants and on the DS Thus, Cellulosic Bicomponent Fibers esterification with toysl chloride occurs at the primary alcohol but benzoyl chloride gives the C-2 and C-6 derivatives For the reaction of alkali cellulose with chloroacetic acid, the reaction occurs at the C-6 OH at low DS values but as the DS increases the C-2 OH reactivity increases The physical properties of cellulose derivatives increase with molecular weight up to a certain value (as is the case with all polymers) and then level off However, the higher the molecular weight, the higher is the melt and solution viscosity Thus, for spinning fibers, casting films or molding, there is an optimum molecular weight or DP 1181 cellulose backbone, hence the common nomenclature, cellulose acetate.] These esters were first produced early in the 19th century and resulted in changes in both military and industrial technology For example, gun cotton replaced black powder as a propellant, and celluloid was an early synthetic thermoplastic that initiated the molding and fabrication of plastics Cotton linters are the preferred source of cellulose raw material as wood pulp gives lower yields The DS of cellulose nitrates may be adjusted by variation in the reactant concentrations and reaction conditions For gun cotton, a high-DP (f2000) cellulose is used and a DS of 2.4–2.8 For lacquers, a DP of about 200 and a DS of 1.9– 2.3 is satisfactory Cellulose Phosphate This derivative has some noteworthy properties It has a high degree of flame resistance and ion-exchange capability It is prepared by treating cellulose with phosphorous oxychloride (POCl3) in pyridine with the introduction of chlorine [16] or with a mixture of phosphoric acid and urea at 150jC [17] Water-soluble cellulose phosphate of high viscosity and DS was prepared by Katsuura et al by treating pulp, preswollen with zinc chloride, with phosphoric acid in molten urea at 150jC [18] Acetylation of cellulose is industrially performed either retaining the gross morphology of the fibers (fiber acetylation) or with a transition from an initially heterogeneous to a homogeneous reaction system (solution acetylation) In both cases, a fully substituted cellulose triacetate (CTA) is obtained, as the reaction product in the fibrous state or dissolved in the reaction system, respectively Cellulose Triacetate Strictly speaking, CTA should have a DS of However, according to the U.S Federal Trade Commission if not less than 92% of the cellulose hydroxyl groups are acetylated the term ‘‘triacetate’’ may be used The acetyl value, or the weight percent of ethanoate groups in the polymer, of commercial CTA for fiber production is 44.3– 44.8% (or a DS of ca 3) but commercial CTA for other uses is about 40.5% (DS = 2.6) Generally, the raw material for CTA is wood pulp or cotton linters of high a-cellulose content The term acellulose refers to the portion of the cellulosic raw material that is insoluble after treatment with an aqueous solution of sodium hydroxide of 17–18% The acetylation, at least initially, is heterogeneous and topochemical wherein successive layers of cellulose fibers react and are solubilized in the reaction medium, thus exposing new surface for reactions The cellulose fibers are mixed with sulfuric acid as a catalyst and suspended in a mixture of acetic anhydride and acetic acid The anhydride is used in slight excess compared to the acetic acid The sulfuric acid reacts with acetic anhydride to form acetylsulfuric acid As the DS approaches the ester is soluble in the reaction mixture The reaction is diffusion-controlled; that is, the reaction rate is controlled by the rate of diffusion of H2SO4 and acetic acid into the fibrous mass Actually, the H2SO4 reacts faster than the acetic anhydride, and cellulose sulfate (CellOSO3H) is formed initially [19] Transesterification then occurs resulting in an acetyl substituent Malm and Tanghe [20] showed sulfation occurs preferentially at the primary hydroxyl group Esters of Organic Acids The cellulose esters of organic acids are undoubtedly the most important cellulose derivatives from both technological and commercial aspects Of the esters, the cellulose acetates dominate the field Cellulose acetates are prepared by reacting the hydroxyl groups on the anhydroglucopyranose units of cellulose with ethanoic anhydride (i.e., acetic anhydride), to a DS of ca [Acetate is the trivial name for the ethonate groups (CH3COOÀ) that are pendant on the The reactions are exothermic so temperature control is important to prevent thermal degradation of the polymers As H2SO4 will also cause degradation, incremental addition of magnesium acetate is employed to remove the acid A Cellulose Esters Inorganic Esters Cellulose nitrate is probably the oldest cellulose ester of commercial importance Cellulose carbonate, cellulose sulfate, cellulose nitrite, and cellulose phosphate have all been synthesized and characterized but only cellulose phosphate shows commercial promise Cellulose Nitrates H2 SO4 CELLOH ỵ HNO3 W CELLONO2 ỵ H2 O H2 O Copyright 2005 by Marcel Dekker 1182 Gilbert and Kadla released during transesterification Magnesium oxide or carbonate also has been used CH3 CO2 ị2 Mg ỵ H2 SO4 WMgSO4 = O ỵ 2CH3 C OH Usually prior to acetylation the cellulose is activated using aqueous or glacial acetic acid Water is the most effective activation agent as it swells the cellulose fibers to a greater extent and eliminates intermolecular hydrogen bonds between the cellulose fibrils and fibers, thus exposing greater surface area However, when water or aqueous acetic acid are used, the cellulose must be dehydrated prior to the acetylation step by using acetic acid to displace the water Other swelling agents, such as ethylene diamine, benzyl alcohol, acetone, ethylene glycol, and C2–C18 carboxylic acids, have been used [21] The acetylation reaction is terminated by addition of water to destroy the excess acetic anhydride This causes rapid hydrolysis of sulfate acid ester but the hydrolysis of the acetyl ester groups is much slower A laboratory procedure for the preparation of CTA is given by Browning [22] Monochloroacetic acid (MCA) or trifluoroacetic acid (TFA) in combination with acetic acid have been used as the reaction medium They convert the acetic acid to the anhydride [23] Perchloric acid has been used as a catalyst in combination with methylene chloride as solvent but has not superseded the sulfuric acid–acetic anhydride, acetic acid process The most difficult and expensive step in the process is the isolation of the CTA in a form suitable for purification and the recovery of the acetic acid By contrast, CTA preparation by fiber acetylation is accomplished wherein part or all of the acetic acid is replaced with an inert diluent, e.g., toluene, benzene, or hexane, to maintain the cellulose fibrous structure during the reaction Perchloric acid is usually employed as the catalyst in this process This process is used exclusively for the preparation of cellulose triacetate CTA is used in plastic applications (e.g., clear screwdriver handles), as films (photographic and food packaging) and lacquers Secondary Cellulose Acetate Secondary cellulose acetate (CDA, DS f 2.4) is prepared by interrupting the acetylation reaction leading to CTA by adding water in the form of aqueous acetic acid of 50–75% concentration This also decreases the level of combined sulfuric acid, which improves the stability of the cellulose acetate Magnesium ions are added to produce insoluble sulfates, further improving the stability of the product The hydrolysis rate is controlled by temperature, catalyst concentration, and, to a smaller extent, by the water content The amount of water influences the ratio of primary to secondary hydroxyl groups in the hydrolyzed cellulose acetate By far the greatest use of secondary cellulose acetate is as cigarette filter tow At a DS of ca 2.4, the cellulose acetate is soluble in acetone and the resulting solution is spun into fibers using solution spinning The removal and Copyright 2005 by Marcel Dekker recovery of the acetone is the most expensive aspect of the spin process An aligned tube of these fibers is the actual ‘‘filter’’ on a cigarette Secondary cellulose acetate fibers are also used in apparels It is used in decorative signs, in films for display packaging due to its excellent clarity, in reverse osmosis films, as a base for transparent pressure sensitive tapes, and in injection molded plastics In hollow fiber form it is used to purify blood and fruit juices Cellulose Monoacetates Buchanan et al [24] have described a highly efficient method for the preparation of water-soluble monoacetates, using a high-temperature, metal-catalyzed, or carboxylicacid-promoted methanolysis of CTA or cellulose diacetate The reactions are run at 155jC under 1000 psi nitrogen pressure using methanol and dibutyl tin oxide or acetic acid as catalysts Cellulose Proprionate, Butyrate, and Mixed Cellulose Esters Other cellulose esters can be produced in a similar manner to the acetates Cellulose propionates, butyrates, and mixed esters of acetates with propionates and butyrates are commercially available These derivatives can be prepared by the reaction of cellulose with the appropriate anhydride and an acid catalyst under conditions similar to these for the cellulose acetates: fiber and solution esterification As the higher organic anhydrides are less reactive than acetic anhydride, higher catalyst concentrations are used For cellulose butyrate, a pretreatment of the cellulose with water and butyric acid is recommended to increase the reaction rate and efficiency As might be expected due to the plasticizing effect of the butyrate groups, cellulose tributyrate has a lower melting point than CTA or the triproprionate and is softer than these esters However, CTB has not been made on a commercial scale Table lists the properties of various cellulose esters Cellulose-mixed esters containing acetate and propionate or butyrate groups have a balance of properties different, and for some applications, superior to the acetates Sulfuric acid is the preferred catalyst for the mixed esterification reaction However, its efficiency decreases as the proportion of the higher-molecular weight acetylating agent in the esterification mixture increases [25] Cellulose acetate propionate is used in flexographic ink formulations The acetate–butyrate mixed esters are used in sheeting, molded plastics, hot melt dip coatings, lacquer coating, and film products The mixed propionate– butyrate ester has excellent compatibility with oil-modified alkyl resins and is used in wood furniture coatings In addition to the direct esterification of the hydroxyl groups, cellulose esters can be produced from transesterification, employing a labile primary substituent, e.g., a nitrite or sulfate group, as the leaving group An advantage of this is that the reaction can be performed in a strictly heterogeneous way, retaining the gross morphology of the original fiber This can permit selective modification of the fiber surface to impart specific chemical/physical fiber Cellulosic Bicomponent Fibers 1183 Table Properties of Cellulose Triesters Moisture Regain (%) Ester M.P (jC) 25% RH 50% RH 75% RH 95% RH Density (g/ml) Tensile strength (mPa) 306 234 183 0.6 0.1 0.1 2.0 0.5 0.2 3.8 1.5 0.7 7.8 2.4 1.0 1.25 1.23 1.17 71.6 48.0 30.4 Acetate Proprionate Butyrate RH = relative humidity Source: Ref 29, p 160 properties Likewise, cellulose esters can readily be deesterified to produce regenerated fibers and films Again, through careful control of reagents and desubstitution conditions, selective desubstitution of the surface can occur wherein a core–sheath morphology can be produced This technique provides a unique opportunity to produce bicomponent fibers with novel properties B Cellulose Ethers The reactions used to prepare cellulose ethers are classical nucleophilic (SN2) reactions of cellulose under alkaline conditions That is, an alkali cellulose is prepared by the treatment of cellulose with a base and a solvating agent (normally aqueous sodium hydroxide) and with an etherifying reagent On a commercial scale the reactions are heterogeneous in nature That is, the cellulose remains in a fibrous or particulate state throughout the reactions The cellulose is activated (swollen) by water, alkali metal hydroxides, liquid ammonia, dimethylformamide, dimethyl sulfoxide, acetic acid, or quaternary ammonium hydroxides However, aqueous NaOH is most commonly used, as it promotes decrystallization of the cellulose and functions as a catalyst for the ether formation Usually ca 18% by weight aqueous NaOH is used above 20jC and the resulting product is termed soda or alkali cellulose CELLOH þ NaOH !CELLO À Methyl Cellulose The first industrial-scale production of a cellulose ether commenced with methyl cellulose (MC) in the 1920s in Germany CELLO Naỵ ỵ CH3 Cl þ Na þ H2 O However, the exact nature of this polyelectrolyte has never been determined Preparation of carboxymethyl cellulose and the hydroxylated alkyl cellulose ethers utilize dilution-mediated process involving organic diluents such as isopropanol, tbutyl alcohol, acetone, toluene, or dimethyoxy ethane [26] The raw materials are cotton linters, softwood pulp, or dissolving pulp They must be high in alpha-cellulose content, free of metals, and uniformly absorb water and the NaOH solution The other starting materials include alkylene oxides and alkyl chlorides for the preparation of nonionic cellulose ethers, and sodium monochloroacetate for anionic types such as sodium carboxymethyl cellulose The degree of substitution and the substituent distribution among and along the cellulose molecules determine the solubility of the cellulose ether in water and its application properties The ethers prepared using aqueous Copyright 2005 by Marcel Dekker sodium hydroxide tend to have random substituent distributions, but uniform distributions may be obtained using quaternary ammonium bases The most important properties of cellulose ethers are their solubility combined with chemical stability and nontoxicity Water solubility and/or organosolubility can be controlled within wide limits via the constitution and the combination of ether groups at the cellulose chain, as well as the DS, and to some extent via substitution pattern Accordingly, cellulose ethers are generally applied, in the dissolved or highly swollen state, to many areas of industry and domestic life, with the spectrum of applications ranging from auxiliaries in large-scale emulsion or polymerization, through to additives for foodstuffs, paints, and cosmetics As such, cellulose ethers have not been widely used in the fabrication of fibers or films However, the combination of etherification and esterification to form cellulose ether–esters may enable the production of novel cellulosic bers with novel properties !CELLOCH3 ỵ Naỵ Cl The reaction is mildly exothermic Side reactions include: !CH3 OH þ Naþ ClÀ CH3 Cl þ NaOH !CH3 À O-CH3 þ Naþ ClÀ þ H2 O CH3 OH þ CH3 Cl ỵ NaOH Commercial methyl cellulose (DS 1.62.0) is soluble in cold water High-DS (2.4–2.8) types are soluble in polar organic solvents Greenway [27] provides a concise description of methyl celluloses and their uses in a number of applications He also discusses the properties and uses of the cellulose ethers Ethyl Cellulose Ethyl cellulose (EC) is prepared by the reaction of alkali cellulose with ethyl chloride: CELLO Naỵ ỵ CH3 CH2 Cl !CELLOUCH2 CH3 ỵ Naỵ Cl 1184 Gilbert and Kadla The DS and substituent distribution are controlled by the reactant molar ratio The main side reactions produce ethanol and diethyl ether, but the product contains carboxylic groups from oxidation of the alkali cellulose and/or the ethyl cellulose Other side reactions include oxidation of ethanol to ethanal (CH3–CHO) and higher aldehydes, which may react with NaOH to produce colored resinous products CH3 CH2 Cl ỵ NaOH ! CH3 CH2 OH ỵ Naỵ Cl CH3 CH2 Cl ỵ CH3 CH2 OH ỵ NaOH ! CH3 CH2 OCH2 CH3 ỵ Naỵ Cl ỵ H2 O The nal reaction mixture contains about 8% ethyl cellulose After dilution to reduce viscosity, the product is precipitated, volatile products flashed off, and the ethyl cellulose filtered off Cellulose Xanthate The formation of cellulose xanthate: þ CELLO Na þ CS2 ! S CELLO À C S Naỵ = is employed in the viscose rayon process [28] Commercially, a vapor phase process is used The DS values are low (ca 1–1.5) as this is sufficient for solubilization of the xanthate in aqueous NaOH for the wet spinning of viscose rayon fibers CELLOC(S)SÀNa+ in aqueous NaOH (17– 18%) is extruded through a spinneret into a coagulation bath consisting mainly of H2SO4 and ZnSO4 to both precipitate the cellulose xanthate and regenerate the cellulose in fiber form Rayon fibers are used to prepare textile fabrics (particularly high-fashion types), often in combination with cotton or polyester, in high-fashion jeans, nonwovens, and special papers (e.g., tea bags) Once the major tire cord for both automotive and truck tires, it has been largely displaced by polyester in automotive tires and Kevlar in truck tires This accounted for a major loss of demand for rayon However, it is still used to a small extent in some automotive tires III POLYMER BLENDING During the past decade intense interest has been focused on polymer blends Polymer blending is a convenient method to develop products with desirable properties Through specific intermolecular interactions, favorable polymer blending can occur and composite materials with desirable properties can be produced There are essentially two ways in which a blend can be made One is by mixing the components in the softened or molten state and the other is to blend them in solution However, as discussed above, cellulose neither melts nor is soluble in convenient organic solvents However, in recent years a variety of new solvent systems for the dissolution of cellulose have been described Copyright 2005 by Marcel Dekker [29] As shown in Table 2, these cellulose solvents typically utilize special combinations of solvents As a result, these solvent systems also dissolve many synthetic polymers, opening the way to produce novel, cellulose-based polymer blends Table lists some common blends of cellulose and synthetic polymers [30] Alternatively, the cellulose may be derivatized in order to improve its solubility in common solvents (vide supra) For example, the cellulose acetates with DS > are soluble in acetone, dioxane, dimethylformamide, dimethyl sulfoxide, pyridine, trifluoroethanol, and many other common solvents [31] Polymer blends can be subdivided into different categories The most important distinction is between compatible or miscible blends, and incompatible or immiscible blends Incompatible blends in which the two components consist of separate, well-defined phases or domains represent the majority of all polymer blends Miscible blends that consist of a single phase are in the minority The formation of miscible polymer blends requires that the free energy of mixing be negative In other words, DGmix ¼ DHmix À TDSmix < ð1Þ where T is the temperature and DGmix, DHmix, and DSmix represent, respectively, the free energy, enthalpy, and entropy of mixing In general, DHmix is positive and DSmix is small, so most blends are incompatible, or ‘‘heterogeneous.’’ The immiscible or heterogeneous polymer blends can be further classified in terms of the two phases Three types of phase morphology are generally recognized In the first, the blend consists of a continuous matrix and a discontinuous particulate filler phase In the second, the discontinuous phase is fibrous, and in the third, the two phases are continuous The latter morphology is referred to as an ‘‘interpenetrating polymer network’’ (IPN) blend [32] In the first two types, as the concentration of the ‘‘added’’ polymer increases phase inversion can occur, and the continuous phase can become the discontinuous filler phase Table Cellulose Solvents Trifluoroacetic acid (TFA) [+ chlorinated alkanes] Hydrazine N-Methylmorpholine N-oxide (MMNO) [+ water] N-Ethylpyridinium chloride [+ pyridine or dimethylformamide (DMF)] Dimethyl sulfoxide (DMSO) + methylamine Nitrosylic compounds + polar aprotic solvent [e.g., N2O4 + DMF] Chloral + CH2Cl2 or CHCl3 Chloral + DMSO [+ triethylamine] SO2 + amine + polar solvent SO3 + polar solvent DMSO + paraformaldehyde (PF) N,N-Dimethylacetamide (DMAc) + lithium chloride (LiCl) DMSO + tetraethylammonium chloride (TEAC) Cellulosic Bicomponent Fibers 1185 Table Common Cellulose-Based Polymer Blends Mixing partner Solvent Polyacrylonitrile DMF–NO2 DMAc–LiCl DMSO–PF DMAc–LiCl DMSO–TEAC DMSO–PF DMAc–LiCl DMSO–PF DMAc–LiCl TFA DMAc–LiCl DMAc–LiCl DMAc–LiCl TFA Poly(vinyl alcohol) Poly(N-vinyl pyrrolidone) Poly(4-vinyl pyridine) Poly(2-hydroxyethyl methacrylate) Poly(ethylene terephthalate) Poly(q-caprolactone) Nylon Poly(ethylene oxide) Chitosan Figure shows the three major classes of fiber that can be spun from heterogeneous mixtures [32] The components of side-by-side (Fig 2a) and sheath–core (Fig 2b) fibers are not well mixed The matrix–fibril blend (Fig 2c) consists of small, discrete fibrils of one polymer embedded in a fairly continuous matrix of the other The formation of side-by-side (S/S) and sheath–core (S/C) fibers involves careful control of flow and mixing of the two polymer streams prior to being passed through a spinning head and spinnerette Some complexity is introduced by the large choice of techniques available for mixing the two polymers For example, in wet or dry spinning, the two polymers may first be dry blended prior to being dissolved in the solvent; the two polymers may be dissolved separately then the solutions combined; one polymer may be dissolved and then added to the monomer of the second polymer, which is subsequently polymerized In the latter, the second polymer might form a homopolymer, be grafted to the first polymer (the fiber formed would not be a polymer blend), or undergo some combination of the two In melt spinning, feasible only with cellulose derivatives and thermoplastic synthetic polymers, the two polymers can again be dry blended in chip form, intimately mixed in a shear mixer and melt spun into fibers Conversely, the two polymers could be first extruded and again pelletized to produced polymer blend chips, then re-extruded and melt spun into fiber The various techniques employed can have an effect on fiber properties Both solvent and melt spinning of polymer mixtures can introduce complications In solution spinning, the components may separate by coalescence, whereas in melt spinning interchain chemical reactions may take place In the latter, this is especially true when dealing with condensation polymers Reactions such as transesterification, transamidation, and the formation of transpolyesteramides are of concern, as they can lead to the formation of block copolymers and, ultimately, random copolymers Depending on the fiber morphology desired, e.g., S/S or S/C, interfacial adhesion between the polymer compo- Copyright 2005 by Marcel Dekker nents may or may not be critically important In the S/S fibers, interfacial adhesion is critical, for without adequate adhesion, the fibers would split apart For S/C, interfacial adhesion is not required, as the fibers can be held together physically This is specifically the case in blends prepared to improve dyeability, flame resistance, or antistatic properties [32] Interfacial adhesion is important, however, for improving mechanical properties Interfacial adhesion properties can be improved by methods such as intermingling the components at their interface or by mechanically interlocking them Factors influencing polymer–polymer adhesion have been studied extensively and are reported elsewhere [33] A Cellulose-Based Polymer Blends Cellulose has been blended with several synthetic polymers to form fibers Side-by-side Lyocell/polyester fibers have been extruded for use as paper and textiles [34] Bicomponent fibers were produced by extruding the two polymers in side-by-side relationship, wherein the cellulose was spun from an amine oxide (NMMO) solution and the polyester from a molten state Depending on the structure of the polyester, domain sizes varied from 70 to 1000 nm long and 30 to 400 nm in diameter Polyesters of high carboxyl content tended to produce fibers with relatively small polyester domains, whereas those with relatively low carboxyl content produced fibers with large polyester domains Noteworthy is that the presence of the synthetic polymer lowers the viscosity of the spin solution permitting higher concentrations of cellulose (12–16 wt.%) In fact, though not mentioned, the solutions were probably mesomorphic Cellulose and poly(vinyl alcohol) (PVA) have been blended to produce gel fibers, battery separators, and reinforcing fibers for friction materials [35,36] PVA content and flow dramatically effected the macroscopic orientation of the cellulose component in the PVA/cellulose blend gel fibers [35] Increasing PVA content decreased the amount of chain orientation Under the lowest flow rate, with increasing PVA content, the orientational distribution Figure Longitudinal and cross sections of three major classes of fibers prepared from two polymers: (a) side-by-side, (b) sheath–core, and (c) matrix–fibril 1186 deviated from longitudinal to circumferential direction and was attributed to influences of the interactions between the two blend components Wet or dry spinning of PVA and water-insoluble cellulosic polymers produced hydrophilic fibrillatable sea–island bicomponent fibers [36] The fibers reportedly absorb large amounts of alkali solutions and have good heat resistance The spinning process involves the extrusion of a phase-separated DMSO solution containing PVA and CDA into a coagulation bath, followed by saponification with N NaOH and subsequently reacted with HCHO and H2SO4 to give fibrillatable 2000 denier/1000 filaments with 10.2 g/denier tenacity and a breakable temperature of 120jC in H2O Textiles have also been produced from blends of cellulose with polypropylene, polyester, nylon, polyamide, and chitin [37–40] Cellulose/polyamide blends were spun from NMMO The resulting physical properties were similar to cellulose alone; however, the wet abrasion resistance increased with increasing polyamide incorporation Sheath/core bicomponent fibers have been prepared by coating oriented viscose rayon on extruded nylon, polypropylene, or polyester monofilaments In these bicomponent fibers the core(s) controlled the tensile and mechanical properties (hysteresis, bending rigidity, and work recovery), whereas the moisture regain was dominated by the sheath (cellulose) Cellulose acetates have been blended with a wide range of synthetic polymers Sheath–core and side-by-side cellulose fibers have been extruded from blends of cellulose acetate and polypropylene for inclusion in absorbant products like disposable diapers and paper towels [41] Blends of cellulose acetate and polyacrylonitrile are good absorbants and deodorants; [42] they also exhibit greater thermal stability than pure cellulose acetate [43] The strength of cellulose triacetate fibers can be increased by blending with polystyrene or polycaprolactam [44,45] In the case of the S/C fibers, the cellulose acetate was the sheath Cellulose has also been blended with cellulose derivatives to produce fibers with useful properties Dry spinning has been used to produce sheath/core cellulose triacetate/ cellulose acetate fibers for textile uses [46,47] The two acetate dopes of which one contains a quaternary ammonium salt (acts as a saponification catalyst) were cospun to form a bicomponent fiber [47] Upon saponification, the segment containing the ammonium salt is saponified while leaving the other segment unsaponified or substantially less saponified The resulting differential shrinkage causes the filament to crimp producing an S/S morphology with a mechanical interlock between the two domains Antistatic bicomponent fibers have been made from nonconductive polymers through the addition of carbon particles [48] Specifically, cellulose, cellulose acetate, polypropylene, polyethylene terephthalate, nylon, and others were combined with a conductive second component, one of the preceding polymers including interdispersed carbon particles The resulting materials displaced reduced resistivity and enhanced environmental stability relative to conventional polymer films and surface-treated fibers Copyright 2005 by Marcel Dekker Gilbert and Kadla REFERENCES 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Krassig, H.A Cellulose–Structure, accessibility and reactivity Polymer Monographs; Gordon and Breach: New York, 1993; Vol 11 Payen, A Troisieme memoire sur le development vegetaux Extrait des memoires de l’Academie Royale des Sciences: Tomes III des Savants Etrangers, Imprimerie Rotale, Paris, 1842 Ott, E.; Spurlin, H.M.; Graffin, M.W Cellulose Derivatives; Interscience: New York, 1954 Kamide, K.; Iijima, H Recent advances in cellulose membranes In Cellulosic Polymers, Blends and Composites; Gilbert, R.D., Ed.; Hansen: New York, 1994; p 189 Noether, H.D Cellulose triacetate, a material for separating chiral molecules In Cellulosic Polymers, Blends and Composites; Gilbert, R.D., Ed.; Hansen: New York, 1994; p 217 Rawls, R Zero-calorie fat substitute unveiled Chemical and Engineering News 1996, Irvine, J.C.; Hirst, E.L Constitution of polysaccharides VI The molecular structure of cotton cellulose J Chem Soc 1923, 123, 518 Spencer, C.C The acetolysis of cotton cellulose Cellulose Chemie 1927, 10, 61–73 Haworth, W.N Structure of carbohydrates Helv Chim Acta 1928, 11, 534–548 Staudinger, H Die Hochmolekularen Organischen Verbindungen-Kautschuk and Cellulose; Springer Verlag: Berlin, 1932 Rao, V.S.N.; Sundararajan, P.R.; Ramakrishnan, C.; Ramachandran, G.N In Conformation of Biopolymers; Ramachandran, G.N., Ed.; Academic Press: London, 1957; p 721 Haynes, W Cellulose, the Chemical that Grows; Doubleday: New York, 1953 Mohanty, A.K.; Misra, M.; Hinrichsen, G Biofibres, biodegradable polymers and biocomposites: An overview Macromol Mater Eng 2000, 276/277, Mohanty, A.K.; Misra, M.; Drzal, L.T Sustainable biocomposites from renewable resources: Opportunities and challenges in the green materials world Journal of Polymers and the Environment 2002, 10, 19–26 Mohanty, A.K.; Misra, M.; Drzal, L.T GPEC 2003 2002; 69–78 Reid, J.D.; Massero, L.W.; Biras, L.M Preparation and properties of cellulose phosphates Ind Eng Chem 1949, 41, 2831–2835 Katsuura, K.; Nonaka, S Cellulose phosphate I Preparation of cellulose phosphate by the urea–phosphoric acid method Seni-Gakkaishi 1957, 13, 24–28 Katsuura, K.; Fujinami, A Preparation of water-soluble cellulose phosphate Kogyo Kagaeu Zasshi 1968, 71, 771– 772 Malm, C.J.; Tanghe, L.J.; Laird, B.C Preparation of cellulose acetate-action of sulfuric acid Ind Eng Chem 1946, 38, 77–82 Malm, C.J.; Tanghe, L.J Preparation of cellulose acetateaction of sulfuric acid Journal of Industrial and Engineering Chemistry 1946, 38, 77–82 Sered, G.A Cellulose esters, organics—fibers In Encycl of Polym Sci and Eng., 2nd Ed.; Wiley-Interscience: New York, N.Y., 1985; Vol 3, 200–226 Browning, B.L Methods of Wood Chemistry; Interscience: New York, 1967; Vol II Peters, R.H The chemistry of fibers In Textile Chemistry; Elsevier: New York, 1963; Vol I, p 187 Buchanan, C.M.; Edgar, K.T.; Wilson, A.K Preparation Cellulosic Bicomponent Fibers 25 26 27 28 29 30 31 32 33 34 35 36 37 38 and characterization of cellulose monoacetates—The relationship between structure and water solubility Macromolecules 1991, 24 (11), 3060–3064 Clarke, H.T., Malm, C.J Mixed organic esters of cellulose US Patent 2,048,685, 1936 Brewer, R.J.; Bogan, R.I Cellulose ethers In Encycl of Polym Sci and Eng., 2nd Ed.; Wiley-Interscience: New York, N.Y., 1985; Vol 3, p 153 Greenway, T.M Water soluble cellulose derivatives and their commercial use In Cellulosic Polymers, Blends and Composites; Gilbert, R.D., Ed.; Hanser Publications: New York, N.Y., 1994; 133–188 Gilbert, R.D Making strong cellulose fibers CHEMTECH, November 1995, p 44 Klemm, D.; Philipp, B.; Heinze, T.; Heinze, U.; Wagenknecht, W Comprehensive Cellulose Chemistry; Wiley VCH: Weinheim, 1998 Nishio, Y Hyperfine composites of cellulose with synthetic polymers In Cellulosic Polymers, Blends and Composites; Gilbert, R.D, Ed.; Hanser Publications: New York, N.Y., 1994; 95–113 Yang, Y Polymer Data Handbook; Oxford University Press: New York, N.Y., 1999; p 50 Hersch, S.P Polyblend Fibers In High Technology Fibers: Part A; Lewin, M.; Preston, J., Eds.; Marcel Dekker: New York, 1985; 1–7 Israelachvila, J Intermolecular and Surface Forces; Academic Press: New York, N.Y., 1992 Bahia, H.S Modified lyocell fibers and films and production method US Patent 6,258,304 B1, 2001 Yokoyama, F.; Sato, A.; Tsugita, H.; Yamashita, Y.; Mitsuishi, K.; Kawano, M Polarized optical microscopy of cellulose poly (vinyl alcohol) blend gel fibers, Sen’I Gakkaishi 1996, 52 (3), 155–159 Oomori, A.; Yoshimochi, T.; Sano, T.; Kobayashi S.; Naramura, S Hydrophilic fibrillatable sea–island bicomponent fibers comprising vinyl alcohol polymers and cellulosic polymers with high tensile strength and manufacture thereof Japanese Patent 08284021, 1998 Fornes, R.E.; Gilbert, R.D Polymer and Fiber Science: Recent Advances; VCH Publishers, Inc.: New York, N.Y., 1991 Morgenstern, B.; Leillinger, O.; Maron, R Cellulose-based Copyright 2005 by Marcel Dekker 1187 39 40 41 42 43 44 45 46 47 48 polymer blend filaments spun from N-methylmorpholineN-oxide Angewandte Makromolekulare Chemie 1996, 243, 129–142 Hirano, S.; Usutani, A.; Yoshikawa, M.; Midorikawa, T Fiber preparation of N-acylchitosan and its cellulose blend by spinning their aqueous xanthate solutions Carbohydrate Polymers 1998, 37, 311–313 Collier, J.R.; Tao, W.Y.; Collier, B.J Bending of internally reinforced rayon fiber Journal of the Textile Institute 1991, 82 (1), 42–51 Abed, J.-C.; Fallon, D.G Nonwoven absorbent materials containing cellulose ester-containing bicomponent fibers US Patent Application 2002/0177379 A1, 2002 Takeuchi, S.; Hoshino, M.; Ochi, R.; Kasabou, Y.; Sakurai E.; Akasaka, M Acrylic conjugate fibers with good doedorant properties and hygroscopicity consisting of mixtures of 10–40% cellulose acetate and/or cellulose as islands and 60–90% acrylonitrile polymers as sea and manufacture thereof and composites therefrom International Patent Application 2003008678 A1, 2003 Meissner, W.; Berger, W.; Hoffman, H Problems in producing man-made fibers from polymer alloys II Preparation and properties of fibers obtained from polyacrylonitrile-cellulose acetate combinations Faserforschung und Textiltechnik 1968, 19 (9), 407–410 Khakimova, G.F.; Farakhova, F.K.; Shoshina, V.I.; Berenshtein, E.I.; Nikonovich, G.V.; Aikhodzhaev, B.I Fibers from a mixture of cellulose triacetate with polystyrene Khimicheskie Volokna 1983, 4, 37–38 Shoshina, V.I.; Khakimova, G.F.; Farakhova, F.K.; Berenshtein, E.I.; Aikhodzhaev, B.I Investigation of the bioconstituent fibers, spinned from the mixture of triacetate cellulose with incompatible synthetic-polymers Fibers from the melt of mixtures TAC with PCL Cellulose Chemistry and Technology 1987, 21 (1), 85–97 Myles, W.J.; Kunkel, R.K Multicomponent filamentary materials US Patent 3,577,213, 1971 Kunkel, R.K.; Munro, J.G Multicomponent filamentary material formed from waste material US Patent 3,684,648, 1972 Rodriguez, E.; Lindsay J.W.; Streetman, W.E Antistatic bicomponent fibers and methods for making the same US Patent 5,972,499, 1999 Index 2-D Shift correlated spectroscopy (COSY), 10 Small-angle X-ray scattering (SAXS), 2, Sodium chondroitin-6-sulfate-polypeptides interactions, 321 Softwood pulps, 177 2-D FT IR spectroscopy, 177 Sphingoglycolipid, 754 crystal structure, 754 Starch gel, 262 13 C CP-MAS NMR spectra, 262 Starch granule, 591, 607 cristallinity, 593, 607 neutron scattering, 594 X-ray, 594 Starch phosphate, 617, 29 Starch, 219, 397, 591, 605, 608, 614, 617, 618, 976 acetylation, 617, 618 acid thinning, 615 a-Amylase, 609 h-Amylase, 609 amylopetin, 591 amylose, 591 aqueous solution, 592 biopolymer/biopolymer interaction, 597 commercial sources, 605 composition, 605 cross-linking, 618 crystalline laminar layer, 219 derived products, 605 dissolution, 594 enzymolysis, 609 epichlorohydrin, 619 esterification, 616 ethanol production, 976 etherification, 616 gelatinization, 594, 608 glass transition temperature, 598 glucoamylase, 609 a-D-Glucosidase, 610 granule organization, 593 hydroxypropylation, 618 isoamylase, 610 interactions with 1-butanol, 597 interactions with hydrophobic product, 597 macromolecular structure, 591 melting, 594 modification, 614 oxidation, 616 physical chemistry, 591 pregelatinization, 615 retrogradation, 600 saccharification, 976 stabilization, 616 structural relaxation, 599 structure, 605 succinylation, 618 thermal treatment, 615 thermochemical degradation, 397 Starlike surfactants, 1055 structure, 1056 Static light scattering, 189, 191 polysaccharides, 189 Steam treatment, 924 catalyst, 924 Copyright 2005 by Marcel Dekker 1203 Succinoglycans, 415 single-chain helical conformation, 415 structure, 415 Sugar, 749 crystal structure, 749 hydrogen bonding, 749 Sulfated colominic acids, 723 antiviral activity, 723 chemical structure, 723 Sulfated polysaccharides, 841 anti-HIV activity, 842 Sulfated ribopolysaccharides, 844 biological activity, 844 Sulfite pulp, 178 dynamic in-phase FT IR spectra, 178 Syndecans, 731 syndecan-1, 731 syndecan-2 (fibroglycan), 731 syndecan-3 (N-syndecan), 731 syndecan-4, 731 transmembrane proteins, 731 Synthetic amylose, 203 time-dependent aggregation, 203 Synthetic cellulose, 552 Synthetic polysaccharides, 773, 784, 839 anticoagulant properties, 773, 784 biological activities, 839 Synthetic saccharide surfactants, 1057 glycolipids, 1061 structure, 1057 Tamarind, 36 small-angle X-ray scattering, 36 Tamarind seed polysaccharides, 226 galactomannans, 226 Thermal depolymerization, 401 agarose, 403 cellulose, 403 chitosan, 402 n-Carrageenan, 403 pectin, 404 polysaccharides, 401 sodium alginate, 404 sodium hyaluronate, 404 xanthan, 404 Thermomechanical pulp, 180 asynchronous 2-D FT IR spectra, 182 dynamic FT IR spectra, 180 static FT IR spectra, 180 synchronous 2-D FT IR spectra, 181 6-S-Thiosulfate-6-deoxycelluloses, 565 Thrombin, 778 Tight junction, 644 structural composition, 644 Time-resolved IR spectroscopy, 161 Tissue engineering, 817 hydrogels, 818 polysaccharide based hydrogels, 817, 819 p-Toloylacetoxy cellulose, 559 Tosyl celluloses, 566 Transmembrane glycoprotein, 1066 glycophorin, 1066 N,N,N-Trimethyl chitosan chloride, 667 permeation-enhancing properties, 667 structure, 668 1204 Trimethyl chitosan, 653, 673 DNA vaccination, 673 membrane permeability, 653 peptide drug, 653 Trimethylsilyl cellulose, 563, 570 solubility, 570 Tri-O-allyl cellulose, 568 Tri-O-crotyl cellulose, 568 6-O-Triphenylmethyl cellulose, 571 Tunicin cellulose, 56 Two-dimensional (2-D) NMR, 10 Two-dimensional IR correlation analysis, 163 Ultrafiltration membranes, 1091 blend membranes, 1094 cellulose acetate butyrate, 1094 cellulose membranes, 1092 chitin membranes, 1094 chitosan composites, 1095 Unsaturated heparan sulfate Disaccharides, 799 liquid chromatography/mass spectroscopy analysis, 798 Vaccines, 655 chitosan microparticles, 655 chitosan, 655 Diphtheria toxoid, 655 Valonia macrophysa cellulose, 135 raman spectra, 134 Valonia macrophysa, 135 raman spectra, 134 Valonia ramie, 134 raman spectra, 134 Wood cell wall, 492 Wood chips, 1041 diffusion, 1042 impregnation, 1043 penetration, 1041 presteaming, 1041 pretreatment, 1041 Wood fibers, 61, 476 polysaccharides, 476 structure, 61 Wood, 63, 159, 492, 1035, 1146 chemical reactions, 1146 FT IR spectroscopy, 159 microfibril organisation, 63 microwave treatment, 492 world forest, 1036 Copyright 2005 by Marcel Dekker Index Xanthan, 112, 205, 238, 245, 397, 416, 444, 446, 449, 459, 470, 480 acid hydrolysis, 397 chemical structure, 416 commercial products, 449 conformational transition, 240, 459 conformation, 112, 416, 461 double helix, 113, 206, 470 helical conformation, 240, 418 helix-coil transition, 238, 445 Manning’s polyelectrolyte theory, 464 molar mass distribution, 460 molar mass, 460 order-disorder transition, 462 463 ordered conformation, 462, 470 persistence length, 466 primary structure, 205, 459 proton NMR spectra, 418 rheology, 245, 420 solution properties, 462 static light scattering, 466 structure, 480 thermal stability, 419 worm-like dimer model, 469 xanthan lyase, 446 Xanthan-guaran interactions, 293 structures, 293 X-Ray diffraction, 100 crystal structure, 102 measurements, 101 programm LALS, 103 programm PS79, 103 sample preparation, 100 Xylan, 223, 477, 483, 503, 786 chemical structure, 224 organostannanes, 503 oxidation, 483 structure, 477 sulfonation, 786 Xylanases, 1017 activities, 1017 Xylanolytic enzymes, 1019 synergy, 1019 Xyloglucan, 34 molecular model, 34 Xyloglucan aggregates, 35 Xyloglucan gel, 33 supramolecular structure, 33 Zimm plot, 194 pullulan, 194 Rhizobium trifolii, 195 ... NAC a-D-Glc-(1! h-D-Glc-(1! a-D-Man-(1! h-D-Man-(1! a-D-Gal-(1! h-D-Gal-(1! h-D-GlcNAc-(1! a-D-GalNAc-(1! h-D-GalNAc-(1! a-L-Fuc-(1! a-L-Rha-(1! h-D-Xyl-(1! 3-u-Me-a-L-Fuc-(1! 3-u-Me-a-L-Rha-(1!... h-D-laminarabioside h-D-laminarabiose Methyl hepta-O-acetyl-h-D-laminarabioside Methyl hepta-O-acetyl-a-D-laminarabioside Octa-O-acetyl-h-D-laminarabioside Octa-O-acetyl-a-D-laminarabioside Copyright... octa-O-acetyl-h-D-laminarabiose), and by Lamba et al [11] on (methyl hepta-Oacetyl-h-D-laminarabiose) Recently, 3-O-h-D-glucopyranosyl-h-D-glucopyranoside (methyl h-D-laminarabioside) [12] and