Conductive ATO‐acrylate nanocomposite hybrid coatings: Experimental results and modeling

The electrical volume conductivity σ of antimony‐doped tin oxide (ATO)–acrylate nanocomposite hybrid coatings was investigated. The relation between σ and the volume filler fraction p was analyzed for the ATO‐acrylate coatings containing ATO nanoparticles grafted with different amounts of 3‐methacryloxy‐propyl‐trimethoxy‐silane coupling agent. Percolation thresholds were observed at very low filler fractions (1–2 vol %) for the coatings containing ATO nanoparticles with a low amount of surface grafting. A modified effective medium approximation (EMA) model was introduced. This model takes into consideration different distances between adjacent semiconductive particles in the particle network. The model elucidates how self‐arrangement of the particles influences the location of the percolation threshold in the log σ ? p plot. The modified EMA model can successfully explain the multiple transition behavior and the variable percolation thresholds found for the ATO‐acrylate nanocomposite hybrid coatings. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2147–2160, 2007     

Synthesis of P(AA‐SA)/ZnO composite latex particles via inverse miniemulsion polymerization and its application in pH regulation and UV shielding

Poly(acrylic acid‐co‐sodium acrylate)/zinc oxide, P(AA‐SA)/ZnO, composite latex particles were synthesized by inverse miniemulsion polymerization. The ZnO nanoparticles were prepared by hydrothermal synthesis and undergone oleic acid (OA) surface treatment. The X‐ray diffraction pattern and FT‐IR spectra characterized the crystal structure and functional groups of OA‐ZnO nanoparticles. An appropriate formulation in preparing P(AA‐SA) latex particles, ensuring the dominant in situ particle nucleation and growth, was developed in our experiment first. Sodium hydroxide was chosen as a costabilizer, because of its ability to increase the deprotonation of acylic acid and enhance the hydrophilicity of monomer, acrylic acid besides providing osmotic pressure. The growth mechanism of P(AA‐SA)/ZnO composite particles was proposed. The OA‐ZnO nanoparticles were adsorbed on or around the surface of P(AA‐SA) latex particles by hydrophobic interaction, thus enhanced the interfacial tension over latex particles. The P(AA‐SA)/ZnO composite latex particles owned better thermal stability than pure latex particles. The pH regulation capacity was excellent for both ZnO and P(AA‐SA) particles. Combining P(AA‐SA) and ZnO nanoparticles into composite particles, the performance in pH regulation and UV shielding was discussed from our experimental results. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8081–8090, 2008     

Synthesis and characteristics of poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite hollow latex particles and their application as drug carriers

In this work, the poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite hollow latex particles was synthesized by a three‐step reaction. The first step was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly(MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second step was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and N,N′‐methylenebisacrylamide in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles. In the third step, the core–shell latex particles were heated in the presence of ammonia solution to form the crosslinking poly(MAA‐NIPAAm) thermosensitive hollow latex particles. The morphologies of poly(MMA‐MAA)/poly(MAA‐NIPAAm) core–shell latex particles and poly(MAA‐NIPAAm) hollow latex particles were observed. The influences of crosslinking agent and shell composition on the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) core–shell latex particles and poly(MAA‐NIPAAm) hollow latex particles were, respectively, studied. Besides, the poly(MAA‐NIPAAm) thermosensitive hollow latex particles were used as carriers to load with the model drug, caffeine. The effect of various variables on the amount of caffeine loading and the efficiency of caffeine release was investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5203–5214     

Bio‐based copolymers obtained through miniemulsion copolymerization of methyl esters of acrylated fatty acids and styrene

Polymers based on renewable sources are promising materials, and can find many uses in coatings and adhesive applications. The goal of this work was to synthesize and characterize bio‐based styrene/acrylated fatty acid methyl ester (AFAME) copolymer—poly(styrene‐co‐AFAME) prepared by miniemulsion polymerization. The main strategy adopted was to functionalize the bio‐monomer with acrylic acid that was confirmed by ¹H NMR and FTIR measurements, to allow its free‐radical homo‐ or copolymerization with styrene. Poly(styrene‐co‐AFAME) with different AFAME content were obtained and their composition were evaluated by ¹H NMR. Dynamic light scattering measurements throughout the reactions have indicated a very stable colloidal systems and average particles size ranges 100–150 nm. The structural and physical properties of poly(styrene‐co‐AFAME) were investigated by DTG‐DTA, DSC which displayed a decreasing of glass transition temperature with increase of AFAME content. The results showed in this study have indicated that the poly(styrene‐co‐AFAME) can be used in several fields because their characteristics are totally distinct. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1422–1432     

Polypyrrole/poly(N‐isopropylacrylamide‐co‐acrylic acid) thermosensitive and electrically conductive composite microgels

The electrically conductive polypyrrole/dodecylbenzene sulfonic acid/poly(N‐isopropylacrylamide‐co‐acrylic acid) (PPy/DBSA/poly(NIPAAm‐co‐AA)) composite microgels were synthesized by a chemical oxidation of pyrrole in the presence of DBSA as the primary dopant, and poly(NIPAAm‐co‐AA) microgels as the polymeric codopant and template, in which APS was used as the oxidant. It was proposed to prepare “intelligent” polymer microgel particles containing both thermosensitive and electrically conducting properties. The polymerization of pyrrole took place directly inside the microgel networks, leading to formation of composite microgels and the morphology was observed by transmission electron microscope. PPy particles interacted strongly with microgels, as the acid groups of microgels acted as the polymeric codopant. The composite microgels thus formed showed electrically conducting behavior dependent on humidity and temperature. At temperatures lower than lower critical solution temperature, the conductivity decreased with increasing the humidity and a small hysteresis phenomenon was observed. The hysteresis became indistinct when temperature was near volume phase transition temperature. However, after the treatment of high temperature and high humidity, the conductivity increased surprisingly due to the structure reorganization inside the composite microgels. The distinctive functionality of the PPy composite microgels was expected to be utilized in many attractive applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1648–1659, 2006     

Synthesis and characteristics of poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive semi‐hollow latex particles and their application to drug carriers

In this work, the poly(methyl methacrylate‐co‐methacrylic acid)/poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite semi‐hollow latex particles was synthesized by three processes. The first process was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly (MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second process was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and crosslinking agent, N,N′‐methylenebisacrylamide, in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles with solid structure. In the third process, part of the linear poly(MMA‐MAA) core of core–shell latex particles was dissolved by ammonia to form the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles. The morphologies of the semi‐hollow latex particles show that there is a hollow zone between the linear poly(MMA‐MAA) core and the crosslinked poly(MAA‐NIPAAm) shell. The crosslinking agent and shell composition significantly influenced the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) semi‐hollow latex particles. Besides, the poly(MMA‐MAA)/poly(MAA‐NIPAAm) thermosensitive semi‐hollow latex particles were used as carriers to load with the model drug, caffeine. The processes of caffeine loaded into the semi‐hollow latex particles appeared four situations, which was different from that of solid latex particles. In addition, the phenomenon of caffeine released from the semi‐hollow latex particles was obviously different from that of solid latex particles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3441–3451     

Synthesis and characteristics of poly(N‐isopropylacrylamide‐co‐methacrylic acid)/Fe3O4 thermosensitive magnetic composite hollow latex particles

In this study, the poly(NIPAAm–MAA)/Fe₃O₄ hollow latex particles were synthesized by three steps. The first step was to synthesize the poly(methyl methacrylate‐co‐methylacrylate acid) (poly(MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. Following the first step, the second step was to polymerize N‐isopropylacrylamide (NIPAAm), MAA, and crosslinking agent (N,N'‐methylene‐bisacrylamide (MBA)) in the presence of poly(MMA‐MAA) latex particles to form the linear poly(MMA‐MAA)/crosslinking poly (NIPAAm‐MAA) core‐shell latex particles. After the previous processes, the core‐shell latex particles were heated in the presence of NH₄OH to dissolve the linear poly(MMA‐MAA) core in order to form the poly(NIPAAm‐MAA) hollow latex particles. In the third step, Fe²⁺ and Fe³⁺ ions were introduced to bond with the ? COOH groups of MAA segments in the poly(NIPAAm‐MAA) hollow polymer latex particles. Further by a reaction with NH₄OH and then Fe₃O₄ nanoparticles were generated in situ and the poly(NIPAAm‐MAA)/Fe₃O₄ magnetic composite hollow latex particles were formed. The concentrations of MAA, crosslinking agent (N,N'‐methylene bisacrylamide), and Fe₃O₄ nanoparticles were important factors to influence the morphology of hollow latex particles and lower critical solution temperature of poly(NIPAAm–MAA)/Fe₃O₄ magnetic composite hollow latex particles. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Aqueous latex/ceramic nanoparticle dispersions: colloidal stability and coating properties

The effect of pH on the colloidal stability of aqueous dispersions containing antimony-doped tin oxide (ATO) or indium tin oxide (ITO) nanoparticles and poly(vinyl acetate-acrylic) copolymer (PVAc-co-acrylic) latex particles was investigated using experimental observations and Derjiaguin, Landau, Verwey and Overbeek (DLVO) theory. The microstructure, electrical properties and optical properties of composite coatings prepared from various dispersions were also studied. Zeta potential measurements revealed that the isoelectric point (IEP) of ATO nanoparticles was below pH 2.0, that of ITO nanoparticles was at pH approximately 6.0 and that of PVAc-co-acrylic latex was at pH approximately 2.0. ATO/PVAc-co-acrylic dispersions prepared at pH 3 were stable, but those prepared at pH 1.5 formed aggregates, which settled quickly with time. DLVO theory predictions are in accord with these results. Stable ITO/PVAc-co-acrylic dispersions are obtained at a pH of 3.0 and 11.0, but dispersions are not stable at a pH of 6.0, the IEP of ITO. At a pH of 3.0, DLVO results predict attraction between ITO particles and latex particles. Dispersion pH affected the microstructures and properties of ATO (or ITO)/PVAc-co-acrylic coatings. Suspensions that formed aggregates produced coatings with lower percolation thresholds and lower transparencies than those produced from stable suspensions.     

Synthesis and morphology of Fe3O4/polystyrene/poly(isopropylacrylamide‐co‐methyl acrylate acid) magnetic composite latex – 2,2′‐azobis (2‐methylpropionamidine) dihydrochloride as initiator

In this work, Fe₃O₄/polystyrene/poly(N‐isopropylacryl amide‐co‐methylacrylate acid) (Fe₃O₄/PS/P(NIPAAM‐co‐MAA)) magnetic composite latex was synthesized by the method of two stage emulsion polymerization. In this reaction system, 2,2′‐azobis(2‐methyl propionamidine) dihydrochloride (AIBA) was used as initiator to initiate the first stage reaction and second stage reaction. The Fe₃O₄ particles were prepared by a traditional coprecipitation method. Fe₃O₄ particles were surface treated by either PAA oligomer or lauric acid to form the stable ferrofluid. The first stage for the synthesis of magnetic composite latex was to synthesize PS in the presence of ferrofluid by soapless emulsion polymerization to form the Fe₃O₄/PS composite latex particles. Following the first stage of reaction, the second stage of polymerization was carried out by the method of soapless emulsion polymerization with NIPAAM and MAA as monomers and Fe₃O₄/PS latex as seeds. The magnetic composite particles, Fe₃O₄/PS/P(NIPAAM‐co‐MAA), were thus obtained. The mechanism of the first stage reaction and second stage reaction were investigated. Moreover, the effects of PAA and lauric acid on the reaction kinetics, morphology, and particle size distribution were studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3912–3921, 2007     

Synthesis of an alkali‐swellable emulsion and its effect on the rate of polymer diffusion in poly(vinyl acetate‐butyl acrylate) latex films

We describe the synthesis and characterization of a weakly cross‐linked poly(methacrylic acid‐co‐ethyl acrylate) alkali‐swellable emulsion (ASE), as well as an investigation of its influence on the rate of polymer diffusion in latex films. The films examined were formed from poly(vinyl acetate‐co‐butyl acrylate) latex particles containing a small amount of acrylic acid as a comonomer. Polymer diffusion rates were monitored by the energy transfer technique. We found that the presence of the ASE component, either in the acid form or fully neutralized by ammonia or sodium hydroxide, had very little effect on the polymer diffusion rate. However, in the presence of 2 wt % NH₄‐ASE, there was a small but significant increase in the polymer diffusion rate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5632–5642, 2005     

Preparation and clinical application of immunomagnetic latex

Magnetic poly(methyl methacrylate) (PMMA)/poly(methyl methacrylate‐co‐methacrylic acid) [P(MMA–MAA)] composite polymer latices were synthesized by two‐stage soapless emulsion polymerization in the presence of magnetite (Fe₃O₄) ferrofluids. Different types and concentrations of fatty acids were reacted with the Fe₃O₄ particles, which were prepared by the coprecipitation of Fe(II) and Fe(III) salts to obtain stable Fe₃O₄ ferrofluids. The Fe₃O₄/polymer particles were monodisperse, and the composite polymer particle size was approximately 100 nm. The morphology of the magnetic composite polymer latex particles was a core–shell structure. The core was PMMA encapsulating Fe₃O₄ particles, and the shell was the P(MMA–MAA) copolymer. The carboxylic acid functional groups (COOH) of methacrylic acid (MAA) were mostly distributed on the surface of the composite polymer latex particles. Antibodies (anti‐human immunoglobulin G) were then chemically bound with COOH groups onto the surface of the magnetic core–shell composite latices through the medium of carbodiimide to form the antibody‐coated magnetic latices (magnetic immunolatices). The MAA shell composition of the composite latex could be adjusted to control the number of COOH groups and thus the number of antibody molecules on the magnetic composite latex particles. With a magnetic sorting device, the magnetic immunolatices derived from the magnetic PMMA/P(MMA–MAA) core–shell composite polymer latex performed well in cell‐separation experiments based on the antigen–antibody reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1342–1356, 2005     

Synthesis and morphology of an iron oxide/polystyrene/poly(isopropylacrylamide‐co‐methacrylic acid) thermosensitive magnetic composite latex with potassium persulfate as the initiator

In this work, an iron oxide (Fe₃O₄)/polystyrene (PS)/poly(N‐isopropylacryl amide‐co‐methacrylic acid) [P(NIPAAM–MAA)] thermosensitive magnetic composite latex was synthesized by the method of two‐stage emulsion polymerization. The Fe₃O₄ particles were prepared by a traditional coprecipitation method and then surface‐treated with either a PAA oligomer or lauric acid to form a stable ferrofluid. The first stage for the synthesis of the thermosensitive magnetic composite latex was to synthesize PS in the presence of a ferrofluid by emulsion polymerization to form Fe₃O₄/PS composite latex particles. Following the first stage of reaction, the second stage of polymerization was carried out with N‐isopropylacryl amide and methacrylic acid as monomers and with Fe₃O₄/PS latex as seeds. The Fe₃O₄/PS/[P(NIPAAM–MAA)] thermosensitive magnetic particles were thus obtained. The effects of the ferrofluids on the reaction kinetics, morphology, and particle size of the latex were discussed. A reaction mechanism was proposed in accordance with the morphology observation of the latex particles. The thermosensitive property of the thermosensitive magnetic composite latex was also studied. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3062–3072, 2007     

Synthesis and characteristics of poly(N‐isopropylacrylamide‐co‐methacrylic acid)/Fe3O4/poly(N‐isopropylacrylamide‐co‐methacrylic acid) two‐shell thermosensitive magnetic composite hollow latex particles

In this study, the poly(N‐isopropylacrylamide‐methylacrylate acid)/Fe₃O₄/poly(N‐isopropylacrylamide‐methylacrylate acid) (poly(NIPAAm‐MAA)/Fe₃O₄/poly(NIPAAm‐MAA)) two‐shell magnetic composite hollow latex particles were synthesized by four steps. The poly(methyl methacrylate‐co‐methylacrylate acid) (poly(MMA‐MAA)) copolymer latex particles were synthesized first. Then, the second step was to polymerize NIPAAm, MAA, and crosslinking agent in the presence of poly(MMA‐MAA) latex particles to form the linear poly(MMA‐MAA)/crosslinking poly(NIPAAm‐MAA) core–shell latex particles. Then, the core–shell latex particles were heated in the presence of NH₄OH to dissolve the linear poly(MMA‐MAA) core to form the poly(NIPAAm‐MAA) hollow latex particles. In the third step, the Fe₃O₄ nanoparticles were generated in the presence of poly(NIPAAm‐MAA) hollow polymer latex particles and formed the poly(NIPAAm‐MAA)/Fe₃O₄ magnetic composite hollow latex particles. The fourth step was to synthesize poly(NIPAAm‐MAA) in the presence of poly(NIPAAm‐MAA)/Fe₃O₄ latex particles to form the poly(NIPAAm‐MAA)/Fe₃O₄/poly(NIPAAm‐MAA) two‐shell magnetic composite hollow latex particles. The effect of various variables such as reactant concentration, monomer ratio, and pH value on the morphology and volume‐phase transition temperature of two‐shell magnetic composite hollow latex particles was studied. Moreover, the latex particles were used as carriers to load with caffeine, and the caffeine‐loading characteristics and caffeine release rate of latex particles were also studied. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2880–2891     

Cryo-SEM studies of latex/ceramic nanoparticle coating microstructure development

Cryogenic scanning electron microscopy (cryo-SEM) was used to investigate microstructure development of composite coatings prepared from dispersions of antimony-doped tin oxide (ATO) nanoparticles (approximately 30 nm) or indium tin oxide (ITO) nanoparticles (approximately 40 nm) and latex particles (polydisperse, D(v): approximately 300 nm). Cryo-SEM images of ATO/latex dispersions as-frozen show small clusters of ATO and individual latex particles homogeneously distribute in a frozen water matrix. In contrast, cryo-SEM images of ITO/latex dispersions as-frozen show ITO particles adsorb onto latex particle surfaces. Electrostatic repulsion between negatively charged ATO and negatively charged latex particles stabilizes the ATO/latex dispersion, whereas in ITO/latex dispersion, positively charged ITO particles are attracted onto surfaces of negatively charged latex particles. These results are consistent with calculations of interaction potentials from past research. Cryo-SEM images of frozen and fractured coatings reveal that both ceramic nanoparticles and latex become more concentrated as drying proceeds; larger latex particles consolidate with ceramic nanoparticles in the interstitial spaces. With more drying, compaction flattens the latex-latex particle contacts and shrinks the voids between them. Thus, ceramic nanoparticles are forced to pack closely in the interstitial spaces, forming an interconnected network. Finally, latex particles partially coalesce at their flattened contacts, thereby yielding a coherent coating. The research reveals how nanoparticles segregate and interconnect among latex particles during drying.     

Toughening of polycarbonate by core‐shell latex particles: Influence of particle size and spatial distribution on brittle‐ductile transition

The impact toughness of polycarbonate modified with acrylic core‐shell latex particles was investigated. Addition of impact modifiers with size ranging from 115.7 to 231.4 nm can result in maximum impact strength. Equations for spatial distribution of modified particles were proposed to associate the interparticle distance with particle size and modifier volume fraction in terms of two possible morphologies, given by T = d[0.91/(φ)^1/3 ? 1] or T = d[0.88/(φ)^1/3 ? 1]. The influence of particle size on brittle‐ductile transition was also studied. The results indicated that critical interparticle distance was not a definitive value and had a narrow region. Moreover, there existed a linear relationship between critical interparticle distance and modifier size, that is, critical interparticle distance would enlarge with the increasing of core‐shell particle size. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1970–1977, 2010     

Synthesis of SiO2/poly(styrene‐co‐butyl acrylate) nanocomposite microspheres via miniemulsion polymerization

A series of SiO₂/poly(styrene‐co‐butyl acrylate) nanocomposite microspheres with various morphologies (e.g., multicore–shell, normal core–shell, and raspberry‐like) were synthesized via miniemulsion polymerization. The results showed that the morphology of the composite latex particles was strongly influenced by the presence or absence of the soft monomer (butyl acrylate), the particle sizes of the silica, and the emulsifier concentrations. The incorporation of the soft monomer helped in forming the multicore–shell structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3202–3209, 2006     

Starch‐graft‐(synthetic copolymer) latexes initiated with Ce4+ and stabilized by amylopectin

A method is presented for synthesizing surfactant‐free latexes comprising starch‐graft‐(vinyl polymer) starting with a suspension of amylopectin, either native or modified, then using cerium(IV) with either potassium persulfate or glucose to create grafting sites on the starch. Latex particles comprising polystyrene, poly(styrene‐co‐(n‐butyl acrylate)) and poly(vinyl acetate) grafted onto high molecular weight amylopectin were developed, with up to 80% of the starch effectively grafted to the particles. These latexes were colloidally stable against electrolyte (several months in 4 M NaCl). Reaction rates of Ce⁴⁺ with simple sugars and polysaccharides were investigated, as well as the gelation mechanism of the latex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4185–4192, 2007     

Influence of polymer particle size on the percolation threshold of electrically conductive latex‐based composites

Monodispersed copolymer emulsions, each with a different polymer particle size, were used to investigate the effect of particle size on the electrical and thermomechanical properties of carbon black (CB)‐filled segregated network composites. These emulsions were synthesized with equal moles of methyl methacrylate and butyl acrylate, with latex particle size ranging from 83 to 771 nm. The electrical percolation threshold was found to decrease from 2.7 to 1.1 vol % CB as the latex particle size was increased. Microstructural images reveal diminished latex coalescence, and improved CB segregation, with increasing latex particle size. In general, coalescence is shown to increase for all systems with increasing CB concentration. Furthermore, all systems exhibited a similar maximum electrical conductivity plateau of 0.7 S cm^?1, albeit at lower concentration for larger latex particle size. This ability to tailor percolation threshold with latex particle size provides an important tool for manipulating electrical and mechanical properties of polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1547–1554, 2011     

Thermosensitive and control release behavior of poly (N‐isopropylacrylamide‐co‐acrylic acid) latex particles

In this work, poly(N‐isopropylacrylamide‐co‐acrylic acid) (poly(NIPAAm‐AA)) copolymer latex particles (microgels) were synthesized by the method of soapless emulsion polymerization. Poly(NIPAAm‐AA) copolymer microgels have the property of being thermosensitive. The concentration of acrylic acid (AA) and crosslinking agent N,N′‐methylenebisacrylamide were important factors to influence the lower critical solution temperature (LCST) of poly(NIPAAm‐AA) microgels. The effects of AA and crosslinking agent on the swelling behavior of poly(NIPAAm‐AA) microgels were also studied. The poly(NIPAAm‐AA) copolymer microgels were then used as a thermosensitive drug carrier to load caffeine. The effects of concentration of AA and crosslinking agent on the control release of caffeine were investigated. How the AA content and crosslinking agent influenced the morphology and LCST of the microgels was discussed in detail. The relationship of morphology, swelling, and control release behavior of these thermosensitive microgels was established. A new scheme was proposed to interpret the control release of the microgels with different morphological structures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5734–5741, 2008     

Preparation of a xanthate‐terminated dextran by click chemistry: Application to the synthesis of polysaccharide‐coated nanoparticles via surfactant‐free ab initio emulsion polymerization of vinyl acetate

Stable monodisperse poly(vinyl acetate) (PVAc) submicronic latex particles were synthesized by ab initio batch emulsion polymerization using a dextran derivative from renewable resource as an efficient steric stabilizer. The dextranend‐functionalized by a xanthate moiety was synthesized by Huisgen's 1,3‐dipolar cycloaddition (click chemistry). It was applied as a macromolecular RAFT (reversible addition fragmentation chain transfer) agent in surfactant‐free emulsion polymerization of vinyl acetate to form in situ an amphiphilic block copolymer able to efficiently stabilize the latex particles. The method afforded the preparation of high solids content (27%) latices coated by dextran. Both the kinetic study and the molar mass analyses confirmed the involvement of the dithiocarbonate group in the emulsion polymerization process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2845–2857, 2008