Seymour/Carraher’s Polymer Chemistry Seventh Edition ß 2006 by Taylor & Francis Group, LLC ß 2006 by Taylor & Francis Group, LLC Seymour/Carraher’s Polymer Chemistry Seventh Edition Charles E Carraher, Jr Florida Atlantic University Boca Raton, Florida, U.S.A ß 2006 by Taylor & Francis Group, LLC CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2008 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S Government works Printed in the United States of America on acid-free paper 10 International Standard Book Number-10: 1-4200-5102-4 (Hardcover) International Standard Book Number-13: 978-1-4200-5102-5 (Hardcover) This book contains information obtained from authentic and highly regarded sources Reprinted material is quoted with permission, and sources are indicated A wide variety of references are listed Reasonable efforts have been made to publish reliable data 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registered trademarks, and are used only for identification and explanation without intent to infringe Library of Congress Cataloging-in-Publication Data Carraher, Charles E Seymour/Carraher’s polymer chemistry Seventh edition / by Charles E Carraher, Jr p cm Includes bibliographical references and index ISBN-13: 978-1-4200-5102-5 ISBN-10: 1-4200-5102-4 Polymers Polymerization I Seymour, Raymond Benedict, 1912- II Title III Title: Polymer chemistry QD381.S483 2007 547’.7 dc22 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com ß 2006 by Taylor & Francis Group, LLC 2007002479 Foreword Polymer science and technology have developed tremendously over the last few decades, and the production of polymers and plastics products has increased at a remarkable pace By the end of 2000, nearly 200 million tons per year of plastic materials were produced worldwide (about 2% of the wood used, and nearly 5% of the oil harvested) to fulfill the ever-growing needs of the plastic age; in the industrialized world plastic materials are used at a rate of nearly 100 kg per person per year Plastic materials with over $250 billion per year contribute about 4% to the gross domestic product in the United States Plastics have no counterpart in other materials in terms of weight, ease of fabrication, efficient utilization, and economics It is no wonder that the demand and the need for teaching in polymer science and technology have increased rapidly To teach polymer science, a readable and up-to-date introductory textbook is required that covers the entire field of polymer science, engineering, technology, and the commercial aspect of the field This goal has been achieved in Carraher’s textbook It is eminently useful for teaching polymer science in departments of chemistry, chemical engineering, and material science, and also for teaching polymer science and technology in polymer science institutes, which concentrate entirely on the science and technologies of polymers This seventh edition addresses the important subject of polymer science and technology, with emphasis on making it understandable to students The book is ideally suited not only for graduate courses but also for an undergraduate curriculum It has not become more voluminous simply by the addition of information—in each edition less important subjects have been removed and more important issues introduced Polymer science and technology is not only a fundamental science but also important from the industrial and commercial point of view The author has interwoven discussion of these subjects with the basics in polymer science and technology Testimony to the high acceptance of this book is that early demand required reprinting and updating of each of the previous editions We see the result in this new significantly changed and improved edition Otto Vogl Herman F Mark Professor Emeritus Department of Polymer Science and Engineering University of Massachusetts Amherst, Massachusetts ß 2006 by Taylor & Francis Group, LLC ß 2006 by Taylor & Francis Group, LLC Preface As with most science, and chemistry in particular, there is an explosive broadening and importance of the application of foundational principles of polymers This broadening is seen in ever-increasing vistas allowing the promotion of our increasingly technologically dependent society and solutions to society’s most important problems in areas such as the environment and medicine Some of this broadening is the result of extended understanding and application of already known principles but also includes the development of basic principles and materials known to us hardly a decade ago Most of the advancements in communication, computers, medicine, air and water purity are linked to macromolecules and a fundamental understanding of the principles that govern their behavior Much of this revolution is of a fundamental nature and is explored in this seventh edition The text contains these basic principles and also touches on their application to real-life situations Technology is the application of scientific principles In polymers there is little if any division between science and technology Polymers are found in the organic natural world as the building blocks for life itself They are also found as inorganic building blocks that allow construction of homes, skyscrapers, and roads Synthetic polymers serve as basic building blocks of society now and in the future This text includes all three of these critical segments of polymeric materials A basic understanding of polymers is essential to the training of today’s science, biomedical, and engineering students Polymer Chemistry complies with the American Chemical Society’s Committee on Professional Training old and revised guidelines as an advanced or in-depth course It naturally integrates and interweaves the important core areas since polymers are critical to all of the core areas, which in turn contribute to the growth of polymer science Most of the fundamental principles of polymers extend and enhance similar principles found throughout the undergraduate and graduate training of students This allows students to integrate their chemical knowledge illustrating the connection between fundamental and applied chemical information Thus, along with the theoretical information, application is integrated as an essential part of the information As in other areas such as business and medicine, short case studies are integrated as historical material While this text is primarily written as an introductory graduate-level text, it can also be used as an undergraduate text, or as an introductory undergraduate–graduate text The topics are arranged so that the order and inclusion or exclusion of chapters or parts of chapters will still allow students an adequate understanding of the science of polymers Most of the chapters begin with the theory followed by application The most important topics are generally at the beginning of the chapter followed by important, but less critical, sections Some may choose to study the synthesis-intense chapters first, others the analytical= analysis=properties chapters, and yet others to simply read the chapters as they appear in the book All of the elements of an introductory text with synthesis, property, application and characterization are present, allowing this to be the only polymer course taken by an individual or the first in a series of polymer-related courses taken by the student This edition continues in the ‘‘user-friendly’’ mode with special sections in each chapter containing definitions, learning objectives, questions, and further reading Application and theory are integrated so that they reinforce one another There is a continued emphasis on pictorializing, reinforcing, interweaving, and integrating basic concepts The initial chapter is short, allowing students to become acclimated Other chapters can be covered in about a ß 2006 by Taylor & Francis Group, LLC week’s time or less Where possible, difficult topics are distributed and reinforced over several topics The basic principles that apply to synthetic polymers apply equally to inorganic and biological polymers and are present in each of the chapters covering these important polymer groupings The updating of analytical, physical, and special characterization techniques continues The chapter on biological polymers has been expanded so that it is now two chapters The chapter on organometallic and inorganic polymers has likewise been greatly upgraded An additional chapter covering the important area of composites has been added Topics such as blends, multiviscosity oils, cross-linking, microfibers, protein folding, protein site identification, aerogels, carbon nanotubes, breakage of polymer chains, permeability and diffusion, mass spectroscopy, polyethers and epoxies, synthetic rubbers, poly(methyl methacrylate), polyacrylonitrile, and polyurethanes have been added or greatly enhanced A number of new selected topics have been added including nonlinear optical behavior, photo physics, drug design and activity, flame retardants, textiles, water-soluble polymers, hydrogels, and anaerobic adhesives The emphasis on the molecular behavior of materials has been expanded as has been the emphasis on nanotechnology and nanomaterials The practice of including a number of appendices has continued, including an enlargement of the trade names appendix ß 2006 by Taylor & Francis Group, LLC Acknowledgments The author gratefully acknowledges the contributions and assistance of the following in preparing this text: John Droske, Charles Pittman, Edward Kresge, Gerry Kirshenbaum, Sukumar Maiti, Alan MacDiarmid, Les Sperling, Eckhard Hellmuth, Mike Jaffe, Otto Vogl, Thomas Miranda, Murry Morello, and Graham Allan; and a number of our children who assisted in giving suggestions for the text: Charles Carraher III, Shawn Carraher, Colleen Carraher-Schwarz, Erin Carraher, and Cara Carraher—to Erin for discussions on materials, Cara for her help with the biomedical material, and Shawn for his help in relating the business and industrial aspects Special thanks to Gerry Kirshenbaum for his kind permission to utilize portions of my articles that appeared in Polymer News This book could not have been written except for those who have gone before us, especially Raymond Seymour, Herman Mark, Charles Gebelein, Paul Flory, and Linus Pauling; all of these friends shepherded and helped me My thanks to them I thank Girish Barot, Amitabh Battin, and Randy Doucette, for their assistance in proofing I also thank my wife Mary Carraher for her help in proofing and allowing this edition to be written ß 2006 by Taylor & Francis Group, LLC 708 H2N H2N O O OH OH HS L-phenylalanine or L-cysteine S-phenylalanine or R-cysteine As noted above, with the exception of alanine, the addition of amino acids to form polypeptides allows for a large number of stereochemical isomers to be formed, even considering that all are of the L form But nature does not allow for this diversity and rather selects only one configuration for a sequence to occur in its synthesis of structure-specific proteins such as those employed as enzymes Even those employed for other activities such as muscle have a specific geochemistry In fact, the cell produces only geometry-specific polypeptides Nature is also selective in the geometry involved in nucleic acid synthesis This specificity involves both the base order and the particular sugar employed For DNA the employed sugar is b-2-deoxy-D-ribose, deoxyribose (below left) Deoxyribose has three chiral centers but only one of them is employed in the synthesis of nucleic acids Ribose, the sugar employed in the synthesis of RNA, has four geometric sites (below right) OH HO OH HO O O 2 OH OH OH Now let us examine simple vinyl polymers, with only one site of substitution per repeat unit When we look at a polymer chain, we focus only on combinations of diads or couples For our discussion, we will use segments of poly(vinyl chloride) The geometries can be divided into three general groups The first group, in which the substitutes, or here the chloride atoms, are all identical with adjoining neighbors, comprise meso diads Polymers or sections of polymers that contain meso diads are referred to as isotactic Cl H Cl Cl H Cl H H R R Meso diad Meso diad Meso diad Isotactic poly(vinyl chloride) segment In the second grouping, the geometry of the substitutes alternates on the chiral carbons that contain the chloride atoms Here each diad is racemic Such segments are referred to as syndiotactic ß 2006 by Taylor & Francis Group, LLC 709 Cl H H Cl Cl H H Cl R R Racemic diad Racemic diad Racemic diad Syndiotactic poly(vinyl chloride) segment The third group consists of mixtures of racemic and meso diads These sequences are given the name atactic or ‘‘having nothing to with tacticity or orderly arrangement.’’ Cl H Cl H H H Cl Cl R R Meso diad Racemic diad Meso diad Atactic poly(vinyl chloride) segment Stereoregular polymers are those that contain large ordered segments In truth, even stereoregular polymers contain some atactic regions Even so, polymers that contain large fractions of ordered segments exhibit a greater tendency to form crystalline regions and to exhibit, relative to those containing large amounts of atactic regions, greater stress=strain values, greater resistance to gas flow, greater resistance to chemical degradation, lower solubilities, etc Cl Cl H H H Cl Cl H H Cl H Cl Cl Cl H H H Cl Cl H R R Atactic poly(vinyl chloride) segment While the situation with respect to simple vinyl polymers is straightforward, the tacticity and geometrical arguments are more complicated for more complex polymers Here we will only briefly consider this situation Before we move to an illustration of this let us view two related chloride-containing materials pictured below We notice that by inserting a methylene between the two chlorine-containing carbons the description of the structure changes from racemic to meso Thus, there exists difficulty between the historical connection of meso with isotactic and racemic with syndiotactic Cl H Cl R R H R H Cl H R Cl 2R,3R-dichloro diad Racemic ß 2006 by Taylor & Francis Group, LLC 2R,4S-dichloro diad plus inserted methylene Meso 710 Let us now move to the insertion of another methylene, forming the following segments The first set contains racemic pairs Cl H H Cl R R R R Cl Cl H H 2R,5R-dichloro segment Racemic pairs 2S,5S-dichloro segment The second contains a meso pairing Cl H H Cl R R R R H H Cl Cl 2R,5S-dichloro segment 2S,5R-dichloro segment Meso pair Now let us look at triad segments of our poly(vinyl chloride) The first one had meso adjacent units and is isotactic by definition of the meso, racemic argument but the adjacent chlorides are not on one side of the plane Cl Cl H Isotactic H R R CI H Meso Meso The second pair contains racemic diads and is syndiotactic by the meso, racemic argument but with the chloride atoms on the same side CI CI H H Syndiotactic R R H CI Racemic Racemic ß 2006 by Taylor & Francis Group, LLC 711 We will now consider segments of a polymer derived from the polymerization of propylene oxide Here the simplest approach is to simply consider this an extension of the case immediately above except where the chloride atoms are substituted by methyl radicals and the next methylene is now an oxygen atom Thus, we can make the same assignments based on the meso, racemic considerations H H3C O R Syndiotactic O O H H3C H H3C CH3 H O R O R O Isotactic H H3C H3C H3C Atactic R H H O R O R O H3C H H CH3 Similarly, we can make assignments for poly(lactic acid) except considering that the carbon next to the chloride-containing carbon has a methyl group, the next following methylene is now a carbonyl, and the next following methylene is an oxygen O O H H3C O R R O Syndiotactic O H H3C O H H H3C O O CH3 O R R O Isotactic H3C O H H3C O O H3C H O H O R Atactic R O H3C ß 2006 by Taylor & Francis Group, LLC H O O H CH3 712 ß 2006 by Taylor & Francis Group, LLC 713 Appendix K Statistical Treatment of Measurements In research and product development and control, there exists variability in the particular value measured such as percentage yield, melting point, tensile strength, and electrical conductivity as you repeat the measurement Accuracy concerns how close to the true value your measured value is Unless there is an established value for a particular material, the values you obtain may well contribute to the ‘‘true’’ value Precision deals with the closeness of a group of measurements to one another Today, most modern instruments making spectral measurements collect many spectra in a short time and those measurements undergo some type of statistical treatment, such as FT-IR, so that the statistical treatment of these results has already been completed In comparison, many measurements are done more or less singularly This is true for most physical testing measurements Thus, to evaluate the tensile strength of a polycarbonate plastic sheeting, sample ‘‘dog-bones’’ of the shape given in Figure 14.11 are cut from several sheets picked at random and tested under an appropriate set of conditions These results are then statistically treated and the reported value given along with the variability Following is a brief summary of one of the more common statistical treatments for such measurements The first step involves calculation of the average value (A), which is simply the summation of the individual values (Ai), divided by the number of measurements or observations (n) This is described mathematically as: A ¼ (SAi)=n where the summation is for all of the n values The most common statistical measure of the variability, dispersion, or scatter is the standard deviation (s) defined as: s¼ hX i1=2 ðAi À AÞ2 =n À The smaller the value of s, the greater is the precision of the measurements Some testing calls for the precision to be within some s value such as one s, two s, three s, etc ß 2006 by Taylor & Francis Group, LLC 714 ß 2006 by Taylor & Francis Group, LLC 715 Appendix L Combinatorial Chemistry Langer and coworkers synthesized a series of copolymers containing various amounts of diacrylate and amine monomers, investigating copolymer composition with the ability to act as transport DNA into cells They screened 140 copolymers as synthetic gene-delivery vectors Of these, 56 were able to bind DNA These polymers were then screened for their ability to facilitate the transfer of plasmid DNA into a common monkey cancer cell line Two of the copolymers with quite varied compositions showed good activity—one expected and the other unexpected The expected copolymer composition would have been a selected composition in a typical search and the other would have been omitted Thus, combinatorial-like approaches can offer unexpected results to problems ß 2006 by Taylor & Francis Group, LLC 716 ß 2006 by Taylor & Francis Group, LLC 717 Appendix M Polymerization Reactors Polymerization can occur within glass ampules, large-scale batch reactors, laboratory beakers, flow-through systems, etc The processes used for small preparation in the research laboratory can be similar or dissimilar to those employed for the industrial-scale preparation of pound and larger quantities While the kind or polymerization influences molecular weight and molecular-weight distribution, polymer structure, and composition as well as some of the physical characteristics, the kind of reactor also influences these factors The reactor must allow adequate temperature control, mix of reactants, and, if needed, catalysts (and at times a number of additives), reactant homogeneity, blending=mixing, etc It must also allow for the economical ‘‘mass production’’ of the material While there exists a wide variety of commercial reactors, we will look at only three of the most used styles—batch, plug flow, and continuous stirred tank reactors Batch In batch reactions, the reactants are added (charged) to the reactor, mixed for a specific time and temperature, and then removed (discharged) Batch reactors are generally simple and can vary from relatively small (such as a gallon) to large (several hundred gallons) with the reaction occurring under varying conditions throughout the reaction vessel with time, giving products that vary with time and, secondarily, location within the vessel This second condition is referred to as the polymerization occurring under nonsteady state or unsteady state conditions The general material balance can be described as follows: Rate of monomer flow into reactor ¼ Rate of monomer flow from reactor þ Rate of monomer loss þ through reaction Rate of polymer accumulation in reactor In a batch system the first two terms are zero since monomer is only added once and leaves only once, after the reaction is completed Thus, ¼ Rate of monomer loss through reaction þ Rate of polymer accumulation ¼ d[M ]=dt þ Rp or Àd[M ]=dt ¼ Rp For free radical polymerization we have: Rp ¼ k0 [M][I ]1=2 ¼ k00 [M] or dt ¼ d[M]=k00 [M] ß 2006 by Taylor & Francis Group, LLC 718 Integration gives: log ([M]=[M0 ]) ¼ Àk00 t and 00 [M] ¼ [M0 ]eÀk t and 00 % Conversion ¼ 100 ([M0 ] À [M]=[M0 ]) ¼ 100 (1 À eÀk t ) This was derived assuming uniform concentration because good mixing is important for this relationship to hold It also assumes a constant temperature Both these assumptions are only approached in most batch systems Further, stirring becomes more difficult as conversion increases so that both control of localized temperature and concentration become more difficult In reality, this relationship holds for only a few percentage points of conversion Overall, temperature is a major concern for vinyl polymerizations because they are relatively quite exothermic This is particularly important for bulk polymerizations This, coupled with the general rapid increase in viscosity, leads to the Trommsdorff-like effects Plug Flow (Tubular) A plug flow or tubular flow reactor is tubular in shape with a high length=diameter (l=d) ratio In an ideal case (as in the case of an ideal gas, this only approached reality) flow is orderly with no axial diffusion and no difference in velocity of any members in the tube Thus, the time a particular material remains within the tube is the same as that for any other material We can derive relationships for such an ideal situation for a first-order reaction One that relates extent of conversion with mean residence time, t, for free radical polymerizations is: 00 [M] ¼ [M0 ] eÀk t and k00 ¼ À(1=t) ln ([M]=[M0 ]) Again, while such relationships are important, they are approximate at best For vinyl polymerizations temperature control is again difficult, with temperature increasing from the cooling reactor wall to the center of the tube, and along with high and different viscosities leads to broad molecular weight distributions Further, these factors contribute to differences in initiator and monomer concentrations again leading to even greater molecular weight distributions Continuous Stirred Tank Reactor In the continuous stirred tank reactor (CSTR) instant mixing to achieve a homogeneous reaction mixture is assumed so that the composition throughout the reactor is uniform During the reaction, monomer is fed into the system at the same rate as polymer is withdrawn The ‘‘heat’’ problem is somewhat diminished because of the constant removal of heated products and the addition of nonheated reactants In a CSTR, each reaction mixture component has an equal chance of being removed at any time regardless of the time it has been in the reactor Thus, in a CSTR, unlike the tubular and bach systems, the residence time is variable and can take the exponential form R(t) ¼ eÀt=t where R(t) is the residence time distribution, t the time, and t the mean residence time, which is a ratio of the reactor volume to the volumetric flow rate The residence time distribution ß 2006 by Taylor & Francis Group, LLC 719 TABLE Listing of Selected Polymerization Processes and the Most Industrially Employed Reactor Types Polymerization Reaction Stepwise Chain-free radical Chain-ionic Polymerization Process Batch Plug Flow Solution Bulk Solution Suspension Emulsion Precipitation Solution Precipitation X X X X X X X X X X CSTR X X X X X X influences the mixing effectiveness, which in turn determines the uniformity of the composition and temperature of the reactants in the reactor and ultimately the primary and secondary polymer structure Table contains a listing of selected polymerization processes and the most industrially employed reactor types ß 2006 by Taylor & Francis Group, LLC 720 ß 2006 by Taylor & Francis Group, LLC 721 Appendix N Material Selection Charts In the selection of a material for a specific application many considerations are involved Today, for the most part, charts and other relationships are computerized Here we will look at their use by employing a graphical chart for illustration only Let us consider making a shaft for a blade that mixes salt water with freshwater for controlled saline irrigation The shaft material must be strong and lightweight and able to absorb twisting shear As strength and weight are two important considerations, we will focus on these A mathematical relationship between weight or mass and strength for a cylindrical shaft can be made such that: Mass is proportional to [density=(shear stress)2=3 ] times some safety factors: This tells us that the best lightweight material to make our shaft is a material with a low density=(shear stress)2=3 ratio Often, the inverse of this ratio is employed and given the name performance index, P (There are performance indexes for many different relationships between various physical behaviors.) Here then: P ¼ (shear stress)2=3=density: Taking the log of both sides gives: log P ¼ 2=3 log shear stress À density: Rearrangement gives: log shear strength ¼ 3=2 log þ 3=2 log P: This expression tells us that a plot of the log of the shear strength versus log density will give a family of straight and parallel lines, each with a slope of 3=2 and each straight line corresponding to a different performance index, P These lines are called design guidelines Figure contains a general plot of log shear strength versus density for a number of materials grouped together under a common heading Within each circle are particular materials with appropriate strength and density values For instance, polytetrafluoroethylene exists in the midrange, extreme right on the ‘‘Polymers’’ circle and so has a relatively high density and strength, while polypropylene exists in the upper left corner of the ‘‘Polymers’’ circle and has a relatively low density and good strength Such charts allow the quick focusing in on the general type of material that exhibits needed characteristics ß 2006 by Taylor & Francis Group, LLC 722 10,000 Advanced ceramics 1,000 Strength, MPa Composites 100 Alloys Wood 10 Polymers Polymer foams 0.5 Elastomers 10 Density (g/mL) FIGURE Materials selection chart for a material’s strength as a function of density ß 2006 by Taylor & Francis Group, LLC