Well defined silica polymer core shell hybrids and polymer hollow structures synthesis, characterization and application

WELL-DEFINED SILICA-POLYMER CORE-SHELL HYBRIDS AND POLYMER HOLLOW STRUCTURES: SYNTHESIS, CHRACTERIZATION AND APPLICATIONS LI GUOLIANG NATIONAL UNIVERSITY OF SINGAPORE 2011 WELL-DEFINED SILICA-POLYMER CORE-SHELL HYBRIDS AND POLYMER HOLLOW STRUCTURES: SYNTHESIS, CHRACTERIZATION AND APPLICATIONS LI GUOLIANG M. Sci., Polymer Chemistry and Physics Nankai University 2007 B. Eng., Polymer Science and Engineering Qingdao University of Science and Technology 2004 A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2011 ACKNOWLEDGEMENTS There are many people that deserve thanks for their friendship, advice and support during my time at NUS. I feel that I am very fortunate to be surrounded by so many wonderful and helpful people. Without each of you I would not have been able to accomplish the work described here. First of all, I would like to thank my supervisor, Professor Kang En-Tang, for his guidance to complete my Ph.D. study and thesis work. I am very grateful for his patience and knowledgeable advice. I will forever treasure the friendship built up from our supervisor-student relationship during my study at NUS. Secondly, I would like to thank Prof. Neoh Koon-Gee, Prof. Wang Chi-Hwa for advices and allowing their students collaborating with me, Prof. Srinivasan Madapusi P. and Prof. Lanry Yung Linyue giving me some valuable suggestions and comments during my Oral Qualifying Exam (O-QE) presentation. Furthermore, I thank my collaborators Dr. Liu Gang, Ms Lei Chenlu, Dr. Wang Liang, Dr. Zong Baoyu, and Mr. Liqun Xu, without whom my research cannot be shine enough to get good publications. Further thanks to my 10 FYP (final year project) students, Ms Liu Peilin, Ms Zeng Liming Dawn, Mr. Harjono Sutanto, Ms Tan Yee Ling, Mr. Eng Zhong Sheng Edmund, Mr. Tai Chin An, Ms Shang Ying, Ms Ng Yen Ling Joyce, Ms Yap Joleen, Ms Jiang Haipan. Further thanks to my colleagues Mr. I Zhao Junpeng, Mr. Li Min and Ms Wan Dong, instrument operator Dr. Yuan Zeliang, Mr. Chia, Phai Ann and Mr. Mao Ning, lab officer Xu Yanfang and Alistair, and administrative officer Doris How Yokeleng. I would like to thank the National University of Singapore for proving financial support through my period of candidate. Finally, but not least, I would like to give my special appreciation to my wife Duan Jingjing, who walked along with me during my stay at NUS, and my parents for their support. II TABLE OF CONTENTS ACKNOWLEDGEMENTS . I SUMMARY .VII NOMENCLATURE IX LIST OF FIGURES . X LIST OF SCHEMES . XVII LIST OF TABLES XVIII Chapter Introduction Chapter Literature Review . 2.1 Hollow Polymer Micro- or Nanostructures Suspension Polymerization . Emulsion Polymerization Dendrimers 11 Self-assembly 12 Core-shell Precursors 14 2.2 Precipitation Polymerization and Distillation-precipitation Polymerization 18 2.3 Sol-gel Process 23 2.4 Click Chemistry 25 Chapter Stimuli-responsive Polymeric Hollow Microspheres from Silica/Polymer Core-shell and Alternating Microspheres . 28 3.1 Introduction . 29 3.2 pH-Responsive Hollow Polymeric Microspheres and Concentric Hollow III Silica Microspheres from Silica-Polymer Core-Shell Microspheres 32 3.2.1 Experimental Section . 32 3.2.2 Results and Discussion 37 3.3 Alternating Silica/Polymer Multilayer Hybrid Microspheres Templates for Double-shelled Polymer and Inorganic Hollow Microstructures . 47 3.3.1 Experimental Section . 47 3.3.2 Results and Discussion 52 3.4 Narrowly Dispersed Double-walled Concentric Hollow Polymeric Microspheres with Independent pH and Temperature Sensitivity 65 3.4.1 Experimental Section . 65 3.4.2 Results and Discussion 69 3.5 Conclusions . 77 Chapter Rattle-type Hollow Hybrid Microspheres 79 4.1 Introduction . 80 4.2 Rattle-type Hollow Nanospheres of Mesoporous Silica Shell-Titania Core 82 4.2.1 Experimental Section . 82 4.2.2 Results and Discussion 86 4.3 Hybrid Nanorattles of Metal Core and Stimuli-Responsive Polymer Shell for Confined Catalytic Reactions . 94 4.3.1 Experimental Section . 94 4.3.2 Results and Discussion 98 4.4 Conclusions . 111 Chapter Hairy Particle Surfaces by Living Radical Polymerization and Click Chemistry 113 IV 5.1 Introduction . 114 5.2 Hairy Hybrid Nanoparticles of Magnetic Core, Fluorescent Silica Shell and Functional Polymer Brushes . 118 5.2.1 Experimental Section . 118 5.2.2 Results and Discussion 122 5.3 Hairy Hollow Microspheres of Fluorescent Shell and Temperature-Responsive Brushes via Combined Distillation-Precipitation Polymerization and Thiol-ene Click Chemistry 129 5.3.1 Experimental Section . 129 5.3.2 Results and Discussion 133 5.4 Binary Polymer Brushes on Silica@Polymer Hybrid Nanospheres and Hollow Polymer Nanospheres by Combined Alkyne-Azide and Thiol-Ene Surface Click Reactions . 146 5.4.1 Experimental Section . 146 5.4.2 Results and Discussion 152 5.5 Hairy Hybrid Microrattles of Metal Nanocore with Functional Polymer Shell and Brushes . 162 5.5.1 Experimental Section . 162 5.5.2 Results and Discussion 168 5.6 Hairy Polymer Hollow Nanospheres of Clickable and Bioactive Surface: Synthesis, Characterization and Applications in Imaging and Drug Delivery . 178 5.6.1 Experimental Section . 178 5.6.2 Results and Discussion 186 5.7 Conclusions . 198 Chapter Conclusions and Recommendations for Future Work 200 V REFERENCES . 205 LIST OF PUBLICATIONS . 216 VI SUMMARY Well-defined inorganic/polymer core-shell hybrids and polymer hollow micro-/nanostructures are of great interest because of their diverse applications in chemistry, materials, biomedicine and nanotechnology. The aim of this work was to develop a simple and general approach to the fabrication of functional inorganic/polymer core-shell hybrids and polymer hollow nanostructures with unique morphology and decorated surface functions via a combination of traditional techniques, such as sol-gel chemistry, distillation-precipitation polymerization and living radical polymerization with the newly developed ‘click’ chemistry. The as-prepared polymer hollow micro-/nanospheres (single shell, double shell, rattle-type and hairy hollow particles) could further been explored as drug delivery vehicles in drug delivery systems (DDSs) and nanoreactors in confined catalytic reactions. First of all, narrowly-distributed (or monodispersed) poly(methacrylic acid) (PMAA) hollow microspheres with stimuli-responsive properties have been fabricated from the corresponding silica/polymer composite hybrids via a combined distillation-precipitation polymerization and sol-gel chemistry. By such means, hybrid microsphres with alternating SiO2/PMAA layer were further produced by sol-gel process and distillation-precipitation polymerization. Hollow PMAA microspheres with double-shell structures and PMAA-PNIPAM double shelled hollow microspheres were obtained by selective removal of silica core and inter-layer from the alternating SiO2/PMAA/SiO2/PMAA hybrids in HF solutions. The obtained double-shelled PMAA VII and PMAA-PNIPAM hollow particles could exhibit a reversible volume change to the stimuli of the environmental medium Subsequently, a serial of rattle-type hollow nanospheres with a polymer shell or mesoporous silica shell and various metal nanocore (gold, silver, or anatase titania) were synthesized using the metal/silica core-shell particles as templates. These well-defined rattle hollow hybrid nanospheres, comprising of the two nanostructured functional materials, can be used for confined catalytic reactions as a nanoreactor system. Furthermore, the as-synthesized Ag@air@PMAA hybrid nanorattles with a Ag nanocore, PMAA shell and free space in between. The as-synthesized Ag@air@PMAA hybrid nanorattles were explored as a nanoreactor system for confined catalytic reduction of 4-nitrophenol. The rate of catalytic reaction can be further regulated by controlling molecule diffusion in and out of the stimuli-responsive PMAA shell through the simple variation of environmental stimuli, such as salt (NaCl) concentration of the medium. Lastly, combination of the robust alkyne-azide, thiol-ene ‘click’ chemistry with the living radical polymerization technique has been explored and exhibited a novel strategy for the fabrication of polymer brush-decorated inorganic/polymer core-shell hybrids and polymer hollow spheres. The as-prepared hollow nanospheres with hairy surfaces and multiple functionalities could improve the particle properties and be explored for biomedical applications as a probe for cell imaging and as a vehicle in drug delivery systems (DDSs). VIII hollow microspheres have also been explored as drug vehicles in drug delivery systems. As demonstrated above, the silica inorganic materials could be used as template for the fabrication of polymer hollow structures. Alternatively, the polymers from distillation-precipitation polymerization can also be used as the template for the inorganic silica hollow structures. Selective removal of polymer layer from the Silica@polymer@silica@polymer@silica mulitilayer hybrid microspheres resulted in the concentric hollow silica micropsheres via calcinations at high temperature. Furthermore, Rattle-type hollow spheres of a porous silica shell and anatase titania nanocore have been produced from the corresponding PMMA/TiO2@PMAA@Silica inorganic/polymer hybrid spheres by calcinations at a high temperature. Well-defined mesoporous structure could be controlled via addition of CTAB surfactant during the sol-gel reaction for the silica shell. The rattle-type titania/silica hollow particles have been employed as a nanoreactor system for photo-induced degradation of chemicals in a confined space. Furthermore, a combination of highly efficient ‘click’ chemistry (Huisgen alkyne-azide cycloaddition and thiol-ene reaction) and traditional techniques (sol-gel process and distillation-precipitation polymerization) have been used to construct hairy hollow structure with unique morphology, multiple functions and tailored surface properties. The first step involved the preparation of silica-polymer core-shell hybrids 202 and linear polymer chains from the living radical polymerization (ATRP and RAFT). Then, the surface ‘click’ reaction occurred, giving rise to polymer brush decorated silica-polymer core-shell microspheres of hairy SiO2@PVK-click-PNIPAM SiO2@P(MAA-co-PMA-co-DVB)-click-PS/PEG core-shell microspheres. The novel hairy hollow structures with decorated polymer brushes have the improved special surface properties in the confined catalytic reactions. The present research work has focused on investigating a series of functional core-shell and hollow microstructures based on combination techniques. Despite these efforts, it is still a long way to go to realize the practical applications of these hybrids and hollow particles. In the future work, the functionalization of these hollow structures for specific applications such as nanomedicine should be investigated. For the newly-developed nanotechnology in medicine, or named nanomedicine, it is highly desirable to synthesize the polymer particles in the range of nano-meters, as well as the bio-functions. The polymer particles with the size of below 200 nm in diameter would be good candidates as the drug carrier for the cancer therapy via the “enhanced permeability and retention (EPR) effect”.171-173 The nanoparticles for biomedical applications need the aqueous solubility and biocompatibility. The functionalized nanoparticles allow a long blood circulation of these nanomaterials upon intravenous injection into animal body.174-175 Targeting is one of the most key factors in cancer therapy. Cancer cells can have an enhanced uptake of nutrients with certain receptors (targeting molecules), such as folic acid, vitamins, sugars, as well as proteins. 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A.; Zhang, Y.; Nickles, R.; Cai, W. B.; Steeber, D. A.; Gong, S. Q. Biomaterials 2011, 32, 4151-4160. 179. Hatefi, A.; Canine, B. F.; Wang, Y. H. J Control Release 2009, 138, 188-196. 215 LIST OF PUBLICATIONS A) Articles in Journals 1) Li, G. L.; Xu, L. Q.; Neoh, K. G.; Kang, E. T. Hairy Hybrid Microrattles of Metal Nanocore with Functional Polymer Shell and Brushes. Macromolecules 2011, 44, 2365-2370. 2) Li, G. L.; Tai, C. A.; Neoh, K. G.; Kang, E. T.; Yang, X. L. Hybrid Nanorattles of Metal Core and Stimuli-responsive Polymer Shell for Confined Catalytic Reactions. Polym. Chem. 2011, 2, 1368-1374. 3) Li, G. L.; Wan, D.; Neoh, K. G.; Kang, E. T. Binary Polymer Brushes on Silica@Polymer Hybrid Nanospheres and Hollow Polymer Nanospheres by Combined Alkyne-Azide and Thiol-Ene Surface Click Reactions, Macromolecules 2010, 43, 10275-10282. 4) Li, G. L.; Xu, L. Q.; Tang, X. Z.; Neoh, K. G.; Kang, E. T. Hairy Hollow Microspheres of Fluorescent Shell and Temperature-Responsive Brushes via Combined Distillation-Precipitation Polymerization and Thiol-ene Click Chemistry, Macromolecules 2010, 43, 5797-5803. 5) Li, G. L.; Shi, Q.; Yuan, S. J.; Neoh, K. G.; Kang, E. T.; Yang, X. L. Alternating Silica/Polymer Multilayer Hybrid Microspheres Templates for Double-shelled Polymer and Inorganic Hollow Microstructures, Chem. Mater. 2010, 22, 1309-1317. 6) Li, G. L.; Liu, G.; Li, M.; Wan, D.; Neoh, K. G.; Kang, E. T. Organo- and Water-Dispersible Graphene Oxide-Polymer Nanosheets for Organic Electronic Memory and Gold Nanocomposites, J. Phys. Chem. C 2010, 114, 12742-12748. 7) Li, G. L.; Dawn, Z. L. M.; Wang, L.; Zong, B. Y.; Neoh, K. G.; Kang, E. T. Hairy Hybrid Nanoparticles of Magnetic Core, Fluorescent Silica Shell and Functional Polymer Brushes, Macromolecules 2009, 42, 8561-8565. 8) Li, G. L.; Kang, E. T.; Neoh, K. G.; Yang, X. L. Concentric Hollow Nanospheres of Mesoporous Silica Shell-Titania Core from Combined Inorganic and Polymer Syntheses, Langmuir 2009, 25, 4361-4364. 9) Li, G. L.; Lei, C. L.; Wang, C. H.; Neoh, K. G.; Kang, E. T.; Yang, X. L. Narrowly Dispersed Double-walled Concentric Hollow Polymeric Microspheres with Independent pH and Temperature Sensitivity, Macromolecules 2008, 41, 9487-9490. 10) Li, G. L.; Liu, G.; Kang, E. T.; Neoh, K. G.; Yang, X. L. pH-Responsive Hollow Polymeric Microspheres and Concentric Hollow Silica Microspheres from 216 Silica-Polymer Core-Shell Microspheres, Langmuir 2008, 24, 9050-9055. 11) Li, M.; Li, G. L.; Zhang, Z. G.; Li, J.; Neoh, K. G.; Kang, E. T. Self-assembly of pH-Responsive and Fluorescent Comb-like Amphiphilic Copolymers in Aqueous Media, Polymer 2010, 51, 3377-3386. 12) Wan, D.; Yuan, S. J.; Li, G. L.; Neoh, K. G.; Kang, E. T. A Glucose Biosensor from Covalent Immobilization of Chitosan-Coupled Carbon Nanotubes on Polyaniline-Modified Gold Electrode, ACS Appl. Mater. Interfaces 2010, 2, 3083-3091. 13) Fu, G. D.; Xu, L. Q.; Yao, F.; Li, G. L.; Kang, E. T. Smart Nanofibers with Photo-responsive Surface for Controlled Release, ACS Appl. Mater. Interfaces 2009, 1, 2424-2427. B) Invited Review Fu, G. D.; Li, G. L.; Neoh, K. G.; Kang, E. T. Hollow Polymeric NanostructuresSynthesis, Morphology and Function, Prog. Polym. Sci. 2011, 36, 127-167. C) Conference Paper Li, G. L.; Li, M.; Neoh, K. G.; Kang, E. T. Hairy Hollow Nanospheres of pH-Responsive Poly(methacrylic acid) Shell and Temperature-responsive Poly(N-isopropylacrylamide) Brushes, the 241st ACS National Meeting&Exposition, 2011, Anaheim, California, USA. 217 [...]... mesoporous silica shell- titania core Table 4.2 Size, size distribution and shell thickness of the hybrid nanoparticles Table 5.1 Size, size distribution and shell thickness of the SiO2@PVK core- shell microspheres Table 5.2 Size, size distribution and shell thickness of the SiO2 @polymer nanospheres with surface grafted binary brushes Table 5.3 Size, size distribution and shell thickness of the metal @silica core- shell. .. well- defined hairy core- shell and hairy hollow nanostructures were prepared by incorporation of alkyne-azide and thiol-ene surface ‘click’ reactions to surface modify silica/ polymer core- shell microspheres, such as hairy hollow polymer microspheres with a flurescent poly(N-vinylcarbazole) (PVK) shell and temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) brushes; polymer hollow microspheres... in the concentric hollow silica cages (ka is the apparent first-order rate constant.) Figure 4.7 TEM micrograph of the silver nanocore Figure 4.8 TEM micrographs of the (b) Ag@SiO2 core- shell NPs with different silica shell thickness: (a) and (a’) 8 nm, (b) and (b’) 15 nm, (c) and (c’) 53 nm Figure 4.9 FT-IR spectra of the (a) Ag@SiO2 core- shell- 3 and (b) Ag@SiO2@PMAA core- double shell- 2 NPs Figure... synthesis of PMAA1-PMAA2 hollow microspheres with pH-responsive asymmetric double shells and silica core- double shell hollow microspheres Scheme 3.3 Schematic illustration of the preparation of polymer /silica alternating hybrid microspheres and double-walled concentric hollow polymeric microspheres with independent sensitivity to pH and temperature Scheme 4.1 Combined polymerization and sol-gel reactions... SiO2@PVK-PNIPAM hairy core- shell microspheres, and (d) air@PVK-PNIPAM hairy hollow microspheres Figure 5.7 UV-visible absorption spectra of the (a) SiO2-MPS seed microspheres, (b) SiO2@PVK Core- shell- 2 microspheres and (c) SiO2@PVK-PNIPAM hairy core- shell microspheres Figure 5.8 Fluorescence spectra of the (a) SiO2@PVK Core- shell- 2 microspheres and (b) SiO2@PVK-PNIPAM hairy core- shell microspheres (λEx... core- shell and metal @silica@ polymer core- double shell microspheres XVIII Chapter 1 Introduction 1 In the past decade, hollow polymeric micro- and nanostructures have attracted considerable interest because of their new functionalities and unique physicochemical properties.1-6 The development of hollow polymer structure is reflected by the rapid increase in the number of scientific publications and patents... functionalization of the shell materials The overall purpose of this thesis is to synthesize hollow polymer micro- and nanospheres with novel morphology and functions via a combination of inorganic and polymer synthesis and optimize the applications of these hollow polymer structures in drug delivery and confined catalytic reactions This research focuses on controlling the size, size distribution and novel morphology... trilayer hybrid and (b) the corresponding concentric hollow titania core -silica shell nanospheres Figure 4.5 Nitrogen adsorption-desorption isotherms and the corresponding pore size distribution plot (inset) of the concentric hollow nanospheres with a mesoporous silica shell Figure 4.6 (a) Concentric hollow nanospheres of mesoporous silica shell- titania core as reaction cages for photocatalysis, and (b) the... Generally, polymer hollow particles have been prepared by suspension polymerization, dispersion polymerization, emulsion polymerization, self-assembly, and template-directed synthesis from dendrimers and core- shell precursors An overview of the methods for the preparation of hollow micro- and nanostructures is listed in Table 2.1 Table 2.1 Overview of methods for the preparation of hollow polymer particles.13... emulsion polymerization process.46 Initially, the core particles are synthesized via conventional emulsion polymerization In the second stage, another monomer is added to produce a layer of polymer surrounding the core particles Particles with a core of PMMA and a shell of poly(styrene-divinylbenzene) (P(St-DVB)), a core of poly(butyl acrylate) (PBA) and a shell of PS, a core of P(MMA-MAAC-EGDMA and a shell . 2011 WELL- DEFINED SILICA- POLYMER CORE- SHELL HYBRIDS AND POLYMER HOLLOW STRUCTURES: SYNTHESIS, CHRACTERIZATION AND APPLICATIONS LI GUOLIANG M. Sci., Polymer Chemistry and Physics. WELL- DEFINED SILICA- POLYMER CORE- SHELL HYBRIDS AND POLYMER HOLLOW STRUCTURES: SYNTHESIS, CHRACTERIZATION AND APPLICATIONS LI GUOLIANG . (d) hollow silica nanospheres with an inner titania core after removal of the polymeric templates, (e) mesoporous silica shell under higher magnification, and (f) hollow core- shell nanostructures