SYNTHESIS AND CHARACTERIZATION OF NANOSTRUCTURED MATERIALS USING DISPERSION POLYMERIZATION CHENG DAMING (M. Sc. Nanjing University) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY OF SCIENCE DEPARTMENT OF CHEMISTRY NATIONAL UNIVERSITY OF SINGAPORE 2006 Acknowledgement An enormous amount of credit belongs to a multitude of people for making this research successful. First of all, I would like to thank my supervisor, Prof. Chan Sze On Hardy of Department of Chemistry. I thank you for your excellent guidance, invaluable support and discussions during this work. The linguistic revision of the thesis and manuscripts is also highly appreciated. Science investigation is a field in which the progress of one is always built upon the achievements of others before him. I truly believe that my work would have been impossible without the guidance and help provided by the other people working in the lab. I have had the pleasure of discussing different aspects of this work with Xia Haibing and Zhou Xuedong. From you I have learned a great deal. There is not a single piece of equipment or process in the lab that I have not learned, or learned to better, from Dr. Xu Lingge and Lee Teck Chia. The wisdom you guys have collected over the years is truly remarkable. Meanwhile, I wish to thank Mdm Loy Gek Luan for your training and guidance with TEM and Mr. Lee Yoon Kuang for your help with FT-IR and UV-vis. For contributions of a less technical nature, I am thankful for other research fellows and students in the lab: Dr. Yang Xiaotun, Dr. Liu Feng, Dr. Liu Shouping, Tang Weihua, Zhou Yong, Liu Xiao, Che Huijuan, Zhang Sheng and Xu Changhua. You guys have made the lab a happy home. Finally, I would like to express my deepest thanks to my family. Thanks my parents for giving me the confidence and character to allow me to follow my dreams. Haihua, my beloved wife, your unwavering love and support through every day of this has been a great gift. You never let me forget that there is a wonderful world outside the lab. I Table of Contents Acknowledgement……… …………… .……………………………………………I Table of Contents…………………………………………………… …………… II Summary……………………………….… ………………………… .………….VII List of Publications …… ……………………………………… …………… . IX List of Abbreviations……… ………………………………………………… X List of Tables .…………………………………….……………………… XI List of Figures…… ………………………………… .…………………….…….XII Chapter Introduction………………………………………………………………1 1.1 Overview of Nanostructured Materials……………………………………… 1.2 Conductive Polymer Nanoparticles.…………………………… …………….4 1.2.1 Methods to Improve the Processability of Conducting Polymers………6 1.2.2 Applications of Conducting Polymers………………………………….12 1.2.2.1 Conducting coatings.……………… ………………………….13 1.2.2.2 Analytical and Separation Uses……………………………… .13 1.2.2.3 Diagnostics…………………………………………………… 14 1.2.2.4 Catalysis………………………………………………….…….15 1.3 Polymeric Hollow Nanospheres……………………………………… …….16 1.3.1 Self-assembly Strategy…………………………………………………17 1.3.2 Emulsion / Suspension Polymerization Approach……………… ……19 1.3.3 Template Strategy………………………………………………………22 1.4 Objectives…………………………………………………………………….27 1.4.1 Surface-functionalized PANI-CS and PPy-CS nanoparticles………….28 1.4.2 PPy-CS hollow nanostructures…………………………………………29 1.4.3 PPy-CS Hollow Nanospheres Containing Movable Ag Cores…………29 Chapter Synthesis and characterization of Surface-Functionalized Conducting Polyaniline-Chitosan Nanocomposites……………………… .………31 2.1 Introduction………………………………………………………………… 32 II 2.2 Experimental…………………………………………………………………35 2.2.1 Chemicals………………………………………………………………35 2.2.2 Synthesis of surface-functionalized PANI-CS nanoparticles……….35 2.2.3 Characterizations……………………………………………………….36 2.2.3.1 Ultraviolet-Visible Spectroscopy…………………………….36 2.2.3.2 Transmission Electron Microscopy…………………………….36 2.2.3.3 Colloidal stability………………………………………………37 2.2.3.4 X-ray Photoelectron Spectroscopy…………………………… 37 2.2.3.5 Elemental Analysis…………………………………………… 37 2.2.3.6 Electrical Conductivity Measurement………………………….38 2.2.3.7 Zeta Potential Measurement……………………………………38 2.2.3.8 Fourier Transform Infrared Spectroscopy…………… .………38 2.2.3.9 Thermogravimetry analysis…………………………………….39 2.3 Results and Discussion……………………………………………………….39 2.3.1 Formation of the colloidal dispersion of PANI-CS nanoparticles…… .39 2.3.2. Morphologies and formation mechanism of the PANI-CS nanoparticle41 2.3.3 Effect of reaction parameters on the size of PANI-CS nanoparticles… 47 2.3.4 Effect of reaction parameters on the colloidal stability of PANI-CS dispersion………………………………………………………… .….48 2.3.5 Conductivities………………………………………………………… 51 2.3.6 Zeta potential………………………………………………………… .53 2.3.7 Structural characterizations of the PANI-CS nanocomposite……….54 2.3.8 TG studies of the PANI-CS nanocomposite……………………………56 2.4 Conclusions………………………………………………………………… 59 Chapter Synthesis and characterization of Surface-Functionalized Conducting Polypyrrole-Chitosan Nanocomposites…………… …………………61 3.1 Introduction………………………………………………………………… 62 3.2 Experimental…………………………………………………………………63 3.2.1 Chemicals………………………………………………………………63 III 3.2.2 Synthesis of surface-functionalized PPy-CS nanoparticles……………64 3.2.3 Characterizations……………………………………………………….65 3.3 Results and Discussion……………………………………………………….65 3.3.1 UV-vis spectra of PPy-CS colloid dispersions…………………………65 3.3.2. Morphologies and Formation Mechanism of PPy-CS nanoparticles….67 3.3.3 Effect of Reaction Parameters on the Size of PPy-CS Nanoparticles….73 3.3.4 Effect of Reaction Parameters on the Colloidal Stability of PPy-CS Dispersion………………………………………………………………74 3.3.5 Conductivities………………………………………………………… 77 3.3.6 Zeta Potential………………………………………………………… .79 3.3.7 Structural Characterizations of the PPy-CS Nanocomposite………… 80 3.4 Conclusions ………………………………………………………………….84 Chapter Facile Fabrication of AgCl@Polypyrrole-Chitosan Core-Shell Nanoparticles and Polymeric Hollow Nanospheres… .……………85 4.1 Introduction………………………………………………………………… 86 4.2 Experimental…………………………………………………………………88 4.2.1 Chemicals………………………………………………………………88 4.2.2 Synthesis of AgCl@PPy-CS Core-shell Nanoparticles………………88 4.2.3 Synthesis of PPy-CS Hollow Nanospheres…………………………….89 4.2.4 Characterization .………………………………………………………89 4.2.4.1 Transmission Electron Microscopy…………………………….89 4.2.4.2 Ultraviolet-visible Spectroscopy……………………………….89 4.2.4.3 X-ray Diffraction Pattern……………………………………….90 4.3 Results and Discussion……………………………………………………….90 4.3.1 Illustration of the reaction route…………………………………… 90 4.3.2 Morphologies………………………………………………………… 91 4.3.3 Formation Mechanism………………………………………………….95 4.3.4 Stability of PPy-CS Hollow Nanospheres……………………………97 4.3.5 Structure Characterizations………………………………………… .98 IV 4.3.5.1 UV-vis Absorption Spectroscopy…………………………… 98 4.3.5.2 Powder X-Ray Diffraction Pattern……………………………100 4.4 Conclusions…………………………………………………………………101 Chapter Fabrication of pH-Responsive Polymeric Hollow Nanospheres, Hollow Nanocubes and Hollow Nanoplates……….………………………….103 5.1 Introduction…………………………………………………………………104 5.2 Experimental………………………………………………………………106 5.2.1 Chemicals……………………………………………………………106 5.2.2 Preparation of AgBr@PPy-CS core-shell nanoparticles……………107 5.2.2.1 AgBr@PPy-CS core-shell nanosphere………………………107 5.2.2.2 AgBr@PPy-CS core-shell nanocube………………………….108 5.2.2.3 AgBr@PPy-CS core-shell plate………………………………108 5.2.3 Preparation of PPy-CS hollow nanostructure……………………….109 5.2.4 Characterization……………………………………………………….109 5.3 Results and Discussion………………………………………………… .…110 5.3.1 Formation of PPy-CS Hollow Nanostructures………………………110 5.3.2 Morphologies of PPy-CS Hollow Nanostructures……………………111 5.3.3 Structure Characterization…………………………………………….117 5.3.4 Permeability of the Shell………………………………………….124 5.4 Conclusions…………………………………………………………………126 Chapter Preparation of Polypyrrole-Chitosan Hollow Nanospheres Containing Silver Cores with Different Sizes………… ……………………… .128 6.1 Introduction…………………………………………………………………129 6.2 Experimental Section……………………………………………………….131 6.2.1 Chemicals…………………………………………………………… 131 6.2.2 Preparation of PPy-CS hollow nanospheres………………………… 131 6.2.3 Preparation of Ag@PPy-CS core-shell nanoparticles………… .……132 6.2.4 Characterization……………………………………………………….133 6.3 Results & Discussion……………………………………………………….133 V 6.4 Conclusions…………………………………………………………………141 Chapter Conclusions and Outlook…………… .………………………………143 7.1 Conclusions………………………………………………………… .……144 7.2 Outlook……………………………………………………………………146 References………………………………………………………………………….149 VI Summary Nanostructured materials are becoming of major significance and the technology of their production and use is rapidly growing into a powerful industry. The purpose of this work was to develop simple methods to prepare novel nanostructured materials and to explore their properties. This work focuses on three nanostructures, nanoparticle, hollow nanostructure, and core-shell nanostructure. Dispersion polymerization technique was used in the preparation of these nanostructures. In the first part of this work, two surface-functionalized conducting nanoparticles, PANI-CS and PPy-CS were prepared. Chitosan was developed as the steric stabilizer to prevent the aggregation of polyaniline and polypyrrole. XPS spectrum proved that chitosan was present on the surface of both PANI-CS and PPy-CS nanoparticles. TEM studies showed that PPy-CS nanoparticles had the regular spherical shape while PANI-CS nanoparticles presented a non-spherical shape. TG studies showed that there exist certain chemical interaction between PANI and chitosan. The chemical structure of the PANI-CS and PPy-CS nanocomposite were characterized by FT-IR and UV-vis. In the second part of this work, a facile method was developed for the fabrication of PPy-CS hollow nanostructures with different sizes and shapes. Two silver halides (AgCl and AgBr) were employed as templates for polymer nucleation and growth. Polymeric hollow nanospheres, hollow nanocubes and hollow plate were prepared. Control over particle dimensions (e.g. core shape, core diameter and shell thickness) VII was achieved easily. These hollow nanostructures were extensively characterized using TEM, FT-IR, UV-vis, and XRD. The PPy-CS shell was found to be permeable for small molecules. The permeability of shell was controlled by the pH of the medium. In the last part of this work, a novel photoreduction method was developed for the preparation of PPy-CS hollow nanospheres with movable Ag nanoparticles inside (Ag@PPy-CS). The formation of this novel core-shell nanostructure was a simple photoreduction process. Ag nanoparticle was formed by ultraviolet irradiation in the interior of the PPy-CS hollow nanosphere. TEM images confirmed the formation of core-shell nanostructure. XRD studies proved that the component of the core was metallic Ag. UV-vis studies showed that the surface plasmon absorption of the core-shell nanoparticle could be tuned in the range of 399.5 - 455 nm. PANI-CS and PPy-CS nanoparticles prepared in this work may be suitable in applications such as labels, conducting coatings, electrorheology, and catalysis. The functional amine groups located at the surface of these nanoparticles are of particular useful for these applications. The pH-responsive hollow nanostructures developed in this work may find applications for the protection, delivery, and storage of chemicals with unstable properties or be used as nanoreactors. The Ag@PPy-CS core-shell nanostructures may be used as new drug delivery devices such as smart laserresponsive carrier systems. VIII List of Publications ☆ “Fabrication of pH-Responsive Polymeric Hollow Nanospheres, Hollow Nanocubes and Hollow Nanoplates”, Cheng, D. M.; Xia, H.; Chan, H. S. O. Nanotechnology, 2006, 17, 1661-1667. ☆ “Novel Method for the Preparation of Polymeric Hollow Nanospheres Containing Silver Cores with Different Sizes”, Cheng, D. M.; Zhou, X.; Xia, H.; Chan, H. S. O. Chemistry of Materials, 2005, 17, 3578-3581. ☆ “Synthesis and Characterization of Surface-functionalized Conducting Polyaniline-Chitosan Nanocomposite”, Cheng, D. M.; Xia, H.; Chan, H. S. O. Journal of Nanoscience & Nanotechnology, 2005, 5, 474-481. ☆ “Morphology of Polyaniline Nanoparticles Synthesized in Triblock Copolymer Micelles”, Cheng, D. M.; Ng, S. -C.; Chan, H. S. O. Thin Solid Films, 2005, 477, 19-23. ☆ “Facile Fabrication of AgCl@Polypyrrole -Chitosan Core-Shell Nanoparticles and Polymeric Hollow Nanospheres”, Cheng, D. M.; Xia, H.; Chan, H. S. O. 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Langmuir, 1996, 12, 788. 170 [...]... dispersants or as materials for removal of contaminated waste [138] Size- and shape-persistent hollow spheres can be prepared using a variety of techniques, each of them having its special advantages (and also disadvantages) In the following sections, an overview of the current state of the art in the field of hollow polymer particles preparation will be given Both strengths and weakness of the respective... theoretical and experimental tools and techniques, which increases our understanding of matter in both the micro and the nano regimes A typical example is the development of atomic force and scanning tunneling microscopy, which has led to sophisticated instruments that change the landscapes of surfaces atom by atom Today nanostructured materials have attracted a great deal of attention in many areas as... processability of PPy and PANI include: 6 (ⅰ) chemical modification of pyrrole and aniline monomers, (ⅱ) doping with functionalized organic acids, and (ⅲ) dispersion polymerization using steric stabilizers The first strategy which has been widely attempted in achieving solublization involves functionalization of the starting material with suitable side chain prior to polymerization Pyrrole and aniline... precipitation polymerization) ; and (ⅲ) the macroscopic precipitation of the polymer is prevented by the presence of a suitable stabilizer The principles of steric stabilization and the use of various types and architectures of 8 steric stabilizers have been studied in recent years as the interest in conducting polymers and their processing has increased A variety of polymers, copolymers and particulate stabilizers... evaporation of PANI or PPy dispersions Conductivity and mechanical properties are tuned by varying the composition of the film and the type of stabilizer Eisazadeh et al [114] prepared PANI and PPy dispersion electrochemically Colloids were electrocoagulated at negative potentials and both PANI and PPy-based coatings on metallic surfaces were obtained in this way Kasicka et al [115] investigated the control of. .. nanoparticles (size of Ag: 36 ± 4 nm; (d) Ag@PPy-CS core-shell nanoparticles (size of Ag: 50 ± 6 nm); (e) Ag@PPy-CS core-shell nanoparticles (size of Ag: 60 ± 7 nm)…… 140 Figure 6.5 XRD patterns of (a) PPy-CS hollow nanospheres; and (b) Ag@PPy -CS core-shell nanoparticles (size of Ag: 20 ± 4 nm)……………… 141 XVI Chapter 1 Introduction 1 1.1 Overview of Nanostructured Materials Nanostructured materials have... of the sample.)………………………………………………………… 83 Figure 4.1 Schematic illustration of the preparation of AgCl@PPy-CS core -shell nanoparticles and PPy-CS hollow nanospheres……………… 91 Figure 4.2 TEM images of (a) AgCl nanoparticles; (b) AgCl@PPy-CS nanoparticles; (c) PPy-CS hollow nanospheres Reaction condition: 20 ml of chitosan (1 wt%, in 0.05 M of HNO3), 0.01 g of AgNO3, XIII 0.025 ml of pyrrole, 0.14 g of. .. first uses of nanoscale materials [5] Metal nanoparticles have been widely used in this area The research on the effect of particle size and shape has been and continues to be vigorous Besides, the broad field of colloid chemistry can also be viewed as an early integral part of 2 nanotechnology [6] The significant advance in nanomaterials is made possible due to the development of theoretical and experimental... Introduction of small quantities of PANI dispersion was found to accelerate the polymerization of aniline both in precipitation and dispersion mode [129] Huang et al [130] prepared PANI and PPy colloids stabilized with colloidal silica These colloids were able to uptake palladium from aqueous solutions PANI colloids offer a large specific surface area compared to other forms of PANI and can act as a catalyst... in dispersion polymerization in aqueous media The dispersion polymerization produces particles of submicrometer size Dispersion polymerization has several typical features: (ⅰ) the monomer is miscible with the reaction medium (in contrast to emulsion or suspension polymerization) ; (ⅱ) the polymer produced during the polymerization is insoluble under the same conditions (like in the precipitation polymerization) ; . SYNTHESIS AND CHARACTERIZATION OF NANOSTRUCTURED MATERIALS USING DISPERSION POLYMERIZATION CHENG DAMING (M. Sc. Nanjing. 1 1.1 Overview of Nanostructured Materials Nanostructured materials have attracted great research interest and the technology of their production and use is rapidly growing into. VI Summary Nanostructured materials are becoming of major significance and the technology of their production and use is rapidly growing into a powerful industry. The purpose of this work