Organic solvent‐free catalytic hydrogenation of diene‐based polymer nanoparticles in latex form: Part I. Preparation of nano‐substrate

Poly(butadiene‐co‐acrylonitrile) (NBR) nanoparticles were synthesized in a semibatch emulsion polymerization system using Gemini surfactant trimethylene‐1,3‐bis (dodecyldimethylammonium bromide), referred to as Gemini‐type surfactant (GS) 12‐3‐12, as the emulsifier. In this polymerization system, an enhanced decomposition rate of initiator ammonium persulfate was achieved even under the low temperature of 50 °C which is attributed to the acidic initiation environment provided using GS 12‐3‐12. The microstructure and copolymer composition of the polymer nanoparticles were characterized by Fourier‐transformed infrared and ¹H nuclear magnetic resonance spectroscopy. The effects of the surfactant concentration on the particle size, zeta potential, polymerization conversion, copolymer composition, molecular weight, and glass transition temperature (T_g) were investigated. It was found that the particle diameter can be controlled by the surfactant concentration and monomer/water ratio and particle sizes below 20 nm can be reached. The obtained latex particles exhibit a spherical morphology. A kinetic study of the copolymerization reaction was carried out, which indicated that an azeotropic composition was produced. The synthesized fine NBR nanoparticles can be employed as the nano substrate for a subsequent hydrogenation process so as to overcome the challenge involved in the field of latex hydrogenation of polymers, which can be found in a related report: Organic Solvent‐Free Catalytic Hydrogenation of Diene‐based Polymer Nanoparticles in Latex Form: Part II. Kinetic Analysis and Mechanistic Study. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Organic solvent‐free catalytic hydrogenation of diene‐based polymer nanoparticles in latex form. Part II. Kinetic analysis and mechanistic study

The central challenge that has limited the development of catalytic hydrogenation of diene‐based polymer latex (i.e., latex hydrogenation) in large‐scale production pertains to how to accomplish the optimal interplay of accelerating the hydrogenation rate, decreasing the required quantity of catalyst, and eliminating the need for an organic solvent. Here, we attempt to overcome this dilemma through decreasing the dimensions of the polymer substrate (such as below 20 nm) used in the hydrogenation process. Very small diene‐based polymer nanoparticles were synthesized and then used as the substrates for the subsequent latex hydrogenation. The effects of particle size, temperature, and catalyst concentration on the hydrogenation rate were fully investigated. An apparent first‐order kinetic model was proposed to describe the rate of hydrogen uptake with respect to the concentration of the olefinic substrate (C?C). Mass transfer of both the hydrogen and catalyst involved in this solid (polymer)–liquid (water)–gas (hydrogen) three‐phase latex system is discussed. The competitive coordination of the catalyst between the C?C and acrylonitrile units within the copolymer was elucidated. It was found that (1) using very small diene‐based polymer nanoparticles as the substrate, the hydrogenation rate of polymer latex can be increased vastly to achieve a high conversion of 95% while a quite low level of catalyst loading is required; (2) this latex hydrogenation process was completely free of organic solvent and no cross‐linking was found; (3) the mass transfer of hydrogen is not a rate‐determining step in the present hydrogenation reactions; (4) the catalyst was dispersed homogeneously within the polymer nanoparticles; (5) for the reaction that has reached about 95 mol % conversion, the kinetic study shows that the reaction is chemically controlled with an apparent activation energy of 100–110 kJ/mol; (6) the strong coordination of C[tbond]N to the catalytically active species RhH₂Cl(PPh₃)₂ imposed a negative effect on the hydrogenation activity. The present research provides a comprehensive study to appreciate the underlying chemistry of latex hydrogenation of diene‐based polymer nanoparticles and more importantly shows great promise toward the commercialization of a “green” catalytic hydrogenation operation of a diene‐based polymer latex in industry. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preparation of poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) core–shell nanoparticles

Poly(methyl methacrylate)–poly(acrylonitrile‐co‐butadiene) (PMMA–NBR) core–shell structured nanoparticles were prepared using a two‐stage semibatch microemulsion polymerization system with PMMA and NBR as the core and shell, respectively. The Gemini surfactant 12‐3‐12 was used as the emulsifier and found to impose a pronounced influence on the formation of core–shell nanoparticles. The spherical morphology of core–shell nanoparticles was observed. It was found that there exists an optimal MMA addition amount, which can result in the minimized size of PMMA–NBR core–shell nanoparticles. The formation mechanism of the core–shell structure and the interaction between the core and shell domains was illustrated. The PMMA–NBR nanosize latex can be used as the substrate for the following direct latex hydrogenation catalyzed by Wilkinson's catalyst to prepare the PMMA–HNBR (hydrogenated NBR) core–shell nanoparticles. The hydrogenation rate is rapid. In the absence of any organic solvent, the PMMA–HNBR nanoparticles with a size of 30.6 nm were obtained within 3 h using 0.9 wt % Wilkinson's catalyst at 130 °C under 1000 psi of H₂. This study provides a new perspective in the chemical modification of NBR and shows promise in the realization of a “green” process for the commercial hydrogenation of unsaturated elastomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Monodispersed PEG‐b‐PSt nanoparticles prepared by atom transfer radical emulsion polymerization under microwave irradiation

Atom transfer radical emulsion polymerization of styrene using PEG‐Cl as macroinitiator under microwave irradiation was successfully conducted and monodispersed nanoparticles were prepared. The PEG‐Cl macroinitiator was synthesized, and confirmed by FTIR spectrum. The structure of the PEG‐b‐PSt diblock copolymer was characterized by ¹H‐NMR and the number of styrene unit in the diblock copolymer was calculated. The morphology, size, and size distribution of the nanoparticles were characterized by transmission electron microscope (TEM) and photon correlation spectroscopy (PCS). The effects of the ratio of macroinitiator and monomer, the ratio of catalyst and macroinitiator on the size and size distribution of nanoparticles were investigated. It was found that the diameters of PEG‐b‐PSt nanoparticles prepared under microwave irradiation were smaller (<50 nm) and more monodispersed than those prepared with conventional heating. Moreover, with the increasing of the ratio of St/PEG‐Cl, the hydrodynamic diameters (D_h) of the nanoparticles increased and the poly index decreased, both D_h and poly index of the nanoparticles prepared under microwave irradiation were smaller then those prepared with conventional heating; as the concentration of catalyst increased, the D_h of the nanoparticles decreased and the poly index of the nanoparticles increased. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 481–488, 2008     

Preparation of monodisperse nanoparticles containing poly(propylene imine)(NH2)32‐polystyrene

Polypropylenimine dendrimer (DAB‐Am‐32, generation 4.0) was converted into a macroinitiator DAB‐Am‐32‐Cl via reaction with 2‐chloropropionyl chloride. Monodisperse nanoparticles containing poly(propylene imine)(NH₂)₃₂‐polystyrene were prepared by emulsion atom transfer radical polymerization (ATRP) of styrene (St), using the DAB‐Am‐32‐Cl/CuCl/bpy as initiating system. The structure of macroinitiator was characterized by FTIR spectrum, ¹H NMR, and ¹³C NMR. The structure of poly(propylene imine)(NH₂)₃₂‐polystyrene was characterized by FT‐IR spectrum and ¹H NMR; the molecular weight and molecular weight distribution of poly(propylene imine)(NH₂)₃₂‐polystyrene were characterized by gel permeation chromatograph (GPC). The morphology, size and size distribution of the nanoparticles were characterized by photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The effects of monomer/macroinitiator ratio and surfactant concentration on the size and size distribution of the nanoparticles were investigated. It was found that the diameters of the nanoparticles were smaller than 100 nm (30–80 nm) and monodisperse; moreover, the particle size could be controlled by monomer/macroinitiator ratios and surfactant concentration. With the increasing of the ratio of St/DAB‐Am‐32‐Cl, the number‐average diameter (D_n), weight‐average diameter (D_w) were both increased gradually. With enhancing the surfactant concentration, the measured D_h of the nanoparticles decreased, while the polydispersity increased. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2892–2904, 2009     

High solids TEMPO‐mediated radical semibatch emulsion polymerization of styrene

A bicomponent initiation system consisting of 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) and the water soluble initiator potassium persulfate (KPS) was used to develop a robust and versatile semibatch emulsion polymerization process to obtain polystyrene (PS) latexes with solids contents of 5–40 wt %. A window of operating conditions was found that yielded high conversion (>95%) stable latexes and well controlled polymers, overcoming limitations found in previous attempts at developing similar processes using TEMPO. The critical parameters studied were surfactant concentration, monomer concentration in the nucleation step and the monomer feed rate in the semibatch step. Methyl acrylate (MA) was used in the nucleation step to improve the nitroxide efficiency (N_Eff). Latexes having molecular weight distribution (MWD) with dispersity (?) lower than 1.5, average particle size (D_p) from ≈32 to ≈500 nm, nitroxide efficiencies N_Eff up to ≈1.0 and monomer conversions >90% were obtained in less than 12 h with solids contents up to 40 wt %. These results constitute a significant advance over prior efforts in TEMPO‐mediated polymerization in aqueous dispersions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 49–62     

Preparation and Stabilization of Emulsifier‐free Macromolecule Nanoparticle Latex Particles

By using acetone‐water as the medium and potassium persulfate (KFS) as the initiator, emulsifier‐free emulsion co‐polymerization of styrene with co‐monomers: MMA, BMA, EA and BDA under microwave irradiation has been investigated. The influence of the each co‐monomer content and hydrophilicity on the hydrodynamic radius R_h of the synthesized copolymer nanoparticles is discussed in detail. The results show mat the increase in ratio of hydrophilic copolymer causes an increase in consumption of the initiator in the initiation reaction, so an increase in the concentration of the surface ? OSO₃ groups which cause the increase in the stability of the latex and gives rise to the formation of smaller micelles. The nano‐particle radius will increase again when the co‐monomer content increases to a certain degree. The curve of the particle hydrodynamic radius vs the co‐monomer content has a minimum point.     

Fabrication and Characterization of Sulfonate‐containing Polystyrene/CaCO3 Core‐shell Nanoparticles

Polystyrene (PSt) seed latex was first prepared via soap‐free emulsion polymerization in the presence of a small amount of methacrylic acid using ammonium persulfate as initiator, and then seeded emulsion polymerization of sodium 4‐styrenesulfonate (NaSS) and St was carried out to synthesize P(St‐NaSS) core latex using 2,2′‐azobisisobutyronitrile as initiator. After that, P(St‐NaSS)/CaCO₃ core‐shell nanoparticles were fabricated by sequentially introducing Ca(OH)₂ aqueous solution and CO₂ gas into the core latex. The morphology of the core and core‐shell nanoparticles was characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM), and the state of CaCO₃ shell was confirmed with high‐resolution scanning transmission electron microscope (HR‐STEM) and selected area electron diffraction (SAED). Results showed that PNaSS chains were successfully grafted onto the PSt seed surface, and length of the PNaSS "hairs" could be modulated by adjusting NaSS amount. Sulfonic groups of the PNaSS hairs served as additives in the formation and stabilization of amorphous CaCO₃(ACC) and prevented ACC from sequent transformation into crystalline states. The amount of the anchored CaCO₃ increased with the growth of PNaSS hair length, and reached 51 wt% (by thermalgravimetric analysis) under the optimal encapsulating temperature of 45°C. Moreover, the forming mechanism of P(St‐NaSS)/CaCO₃ core‐shell nanoparticles was proposed.     

Unseeded semibatch emulsion polymerization of butyl acrylate: Bimodal particle size distribution

Unseeded semibatch emulsion polymerization of butyl acrylate (BA) using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator was carried out at the conditions where secondary nucleation was probable. This was achieved by using no emulsifier in the initial reactor charge. The effects of changes in monomer emulsion feed rate, initiator concentration and distribution, emulsifier concentration in the feed, and temperature on the evolution of particle size averages and distribution were investigated. Bimodal particle size distributions (PSD) were obtained for most of the latexes. Inhibition effects were found to be important in the development of PSD. Primary particle formation occurred through micellar nucleation, whereas secondary nucleation probably occurred through homogenous nucleation. The polydispersity index (PDI) of the latexes increased with the decreasing monomer emulsion feed rate. The application of a larger amount of initiator to the reactor charge or using a higher temperature, reduced the formation of secondary particles and resulted in a formation of an unimodal PSD. The overall steady‐state rate of polymerization was found to approach the rate of monomer addition (R_p ≈ R_a ), if the emulsifier concentration in the aqueous phase was appreciable. This is different from the correlation 1/R_p = 1/K + 1/R_a obtained for the BA semibatch process with neat monomer feed. This suggests that different rate expressions can be used for BA semibatch emulsion polymerization at different conditions. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 528–545, 2000     

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     

Preparation of a Polyethylene Latex by Catalytic Hydrogenation of a Polybuta‐1,4‐diene‐Based Dispersion

Summary: Fully linear polyethylene‐based latexes have been prepared by the hydrogenation of polybuta‐1,4‐diene dispersions. The latter were synthesized via dispersion ring‐opening metathesis polymerization of cycloocta‐1,5‐diene, and hydrogenated using RuCl₂(PPh₃)₃ as catalyst, without any further treatment. A high hydrogenation efficiency was achieved as demonstrated by different techniques including DSC, and ¹H NMR and FT‐IR spectroscopy. The hydrogenation process could be carried out without detrimental effect on particle size and colloidal stability as evidenced by optical microscopy and light scattering analysis.

Optical microscopy photograph of a polybutadiene‐based dispersion after hydrogenation. No change in size is observed.     

Stability of the polymerizable surfactant stabilized latex particles during semibatch emulsion polymerization

The effect of the polymerizable surfactant, sodium dodecyl allyl sulfosuccinate (JS-2), on the stability of polybutyl acrylate latex particles during semibatch emulsion polymerization was investigated in this work. Experimental data show that the ionic strength is the most important parameter in determining the latex stability during the reaction. Both the amount of coagulum produced by intensive coagulation and percentage of the particle volume change (ΔV) caused by limited flocculation increase with increasing electrolyte concentration. The parameter Δ V increases significantly when the concentration of JS-2 in the initial reactor charge ([JS-2]_i) increases. The amount of coagulum increases rapidly when the agitation speed is increased from 400 to 800 rpm. Experiments of coagulation kinetics were carried out to study the stability of latex products toward added salts. The experimental data show that the chemical stability of the latex product increases with increasing pH. Furthermore, the critical coagulation concentration and diffuse potential increase with increasing [JS-2]_i. It is postulated that the increasing electrostatic attraction force between two approaching particles due to the increased [JS-2] _i can increase the apparent magnitude of Hamaker constant.     

Semibatch emulsion polymerization of methyl methacrylate using different polyurethane particles

Aqueous acrylic‐polyurethane (AC–PU) hybrid emulsions were prepared by semibatch emulsion polymerization of methyl methacrylate (MMA) in the presence of four polyurethane (PU) dispersions. The PU dispersions were synthesized with isophorone diisocyanate (IPDI), 1000 and 2000 molecular weight (MW) poly(neopentyl) adipate, 1000 MW polytetramethyleneetherglycol, butanediol (BD), and dimethylol propionic acid (DMPA). MMA was added in the monomer emulsion feed. We studied the effect of the use of different PU seed particles on the rate of polymerization, the particle size and distribution, the number of particles, and the average number of radicals per particle. The PU rigidity was controlled by varying the polyol chemical structure, the polyol MW (M_n), and by adding BD. The monomer feed rate was varied to study its influence on the process. It was observed that the PU particles that had been prepared with a higher MW polyol swelled better with MMA before the monomer‐starved conditions occurred. There seemed to be no significant discrepancies between the series with different PU seeds in the monomer‐starved conditions. The overall conversion depended on the monomer addition rate, and the polymerization rate acquired a constant value that was comparable to the value of the monomer addition rate. The instantaneous conversion increased slightly. The average particle size increased, and the total particle number in the reactor was constant and similar to the number of PU particles in the initial charge. The average number of radicals per particle increased. The differences between the system with a constant particle number and average number of radicals per particle and the system with a fixed radical concentration are discussed. The semibatch emulsion polymerization of MMA in the presence of PU particles studied was better compared to the system with a fixed radical concentration. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 844–858, 2005     

Investigation of cationic soapless P(St-<Emphasis Type="Italic">co</Emphasis>-DMAEMA) latex and its electrostatic adsorption of laponite

Cationic poly(styrene-co-N,N-dimethylaminoethyl methacrylate) (P(St-co-DMAEMA)) latexes were prepared in the absence of surfactant by using 2,2’ -azobis (2-methylpropionamidine) dihydrochloride (AIBA) as the initiator. The effects of the AIBA concentration, HCl/DMAEMA molar ratio and DMAEMA amount on the emulsion polymerization and the latex properties were investigated. The particle morphology and size, the zeta potential and the amino distribution of the P(St-co-DMAEMA) latexes were characterized by transmission electron microscope (TEM), dynamic light scattering (DLS) and conductometric titration, respectively. Results showed that the emulsion polymerization performed smoothly with high monomer conversion and narrow particle size distribution under the optimized conditions with AIBA concentration of 1 wt%, HCl/DMAEMA molar ratio of 1.2 and DMAEMA content of 5 wt%. The diameter of the dried latex particles decreased and the density of amino groups on the particle surfaces increased with increasing the DMAEMA content. The zeta potential of the P(St-co-DMAEMA) latexes was pH-dependent and the zero point was around at pH 7.2. A facile method was developed to fabricate P(St-co-DMAEMA)/laponite hybrid nanoparticles via electrostatic adsorption, in which the loading capacity of laponite platelets reached 17.7 wt%, and the resultant hybrid nanoparticles showed good thermal stability.     

Direct Catalytic Hydrogenation of an Acrylonitrile‐Butadiene Rubber Latex Using Wilkinson's Catalyst

Summary: Hydrogenated acrylonitrile‐butadiene rubber is a high‐performance elastomer that has found important applications in the automobile industry and petroleum fields. A new catalytic process has been investigated for producing hydrogenated acrylonitrile‐butadiene rubber by direct hydrogenation of the rubber in latex form using RhCl(PPh₃)₃ as catalyst. The reactions were achieved without the addition of any organic solvents. This is the first time that the direct catalytic hydrogenation of an acrylonitrile‐butadiene rubber latex has been successfully realized in the absence of any organic solvent with a conversion of higher than 95% without cross‐linking of the polymer.

Effect of RhCl(PPh₃)₃/acrylonitrile‐butadiene rubber ratio on hydrogenation.     

Synthesis of Composite Polystyrene/Silica Nanoparticles via Precipitation and Emulsion Polymerization Methods

Polystyrene/silica composite nanoparticles were synthesized via precipitation and emulsion polymerization methods, in the presence of a basic co‐monomer (e.g., 4‐VP and 1‐VID), and a colloidal aqueous silica solution. The effects of key process parameters, that is, solvent type, monomer/co‐monomer volume ratio and total monomers concentration for precipitation polymerization, and reaction temperature, pH value, initial silica‐sol concentration and initial monomer/co‐monomer molar ratio for emulsifier‐free emulsion polymerization on the particle morphology, silica content, and particle size distribution of the composite nanoparticles were experimentally investigated. Stable, spherical, and uniform in size composite nanoparticles were synthesized by both techniques. The average particle diameter varied from 108 to 182 nm for the emulsifier‐free emulsion polymerization and from 400 to 800 nm for the precipitation polymerization, while the silica content was as high as 38.3 wt.‐% for the former method and up to 15.5 wt.‐% for the later. The synthesized composite polymer/silica particles were then electrolytically co‐deposited with zinc on steel plates to improve the corrosion resistance of the metal's surface.

     

Preparation of novel suspensions of ZnO/living block copolymer latex nanoparticles via pickering emulsion polymerization and their long term stability

In this work, we present the first Pickering emulsion polymerization with a controlled/living character. Pickering emulsion polymerization in the presence of a novel suspension of zinc oxide/poly(sodium 4‐styrenesulfonate) (ZnO/PSS^?) nanocomposite particles was applied to prepare ZnO/living block copolymer latexes. In the emulsion system, 1,1‐diphenylethene (DPE)‐controlled radical polymerization of poly(methyl methacrylate)‐b‐poly(butyl acrylate) (PMMA‐b‐PBA) was proceeded in oil phase. The nanocomposite particles of ZnO/PSS^? with an average diameter of 20 nm and negatively charged zeta potential around ?30 mV were synthesized via hydrothermal method then served as an effective emulsion stabilizer at the oil/water interface. Living polymerization was carried out using DPE‐capped PMMA as the macroinitiator and PMMA‐b‐PBA block copolymer latex was successfully prepared with coverage of ZnO/PSS^? nanoparticles. Narrow size distributions of the droplets as well as latex particles were obtained, and the livingness of block copolymers was comparable to that of emulsions stabilized by conventional surfactants. The controlled/living character in Pickering emulsion polymerization was slightly influenced by the amount of PSS^? immobilized into the ZnO/PSS^? nanoparticles, whereas it was significantly influenced by the weight ratios between ZnO/PSS^? and oil phase. The Pickering latexes showed excellent long term stability against either coalescence or sedimentation over several months. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of Poly(n‐butyl acrylate/methyl methacrylate)/CNC Latex Nanocomposites via In Situ Emulsion Polymerization

Cellulose nanocrystals (CNCs) are renewable, nontoxic and naturally available organic nanoparticles derived from cellulosic resources such as cotton and wood pulp. Poly(n‐butyl acrylate‐co‐methyl methacrylate)/CNC latexes are successfully synthesized via in situ emulsion polymerization. The effect of CNC loading on overall conversion, polymer particle size, glass transition temperature (T_g), gel content, latex viscosity, and storage and loss moduli of dried latex are studied. While the effect of CNC content on overall conversion, polymer particle size, and T_g of the resulting latexes is negligible, significant increase in gel content, latex viscosity, and storage and loss moduli are observed.

     

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     

Emulsion synthesis of nanoparticles containing PEDOT using conducting polymeric surfactant: Synergy for colloid stability and intercalation doping

Poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) is a widely used conductive aqueous dispersion synthesized by using emulsion polymerization method. To further enhance its solution processability and conductivity of PEDOT derivatives, we proposed to replace the nonconductive PSS with conductive poly[2‐(3thienyl)‐ethoxy‐4‐butylsulfonate] (PTEB) as surfactant for the emulsion polymerization of PEDOT. The reaction involved colloid stabilization and doping in one step, and yielded PEDOT:PTEB composite nanoparticles with high electrical conductivity. Contrary to its counterpart containing nonconductive surfactant, PEDOT: PTEB showed increasing film conductivity with increasing PTEB concentration. The result demonstrates the formation of efficient electrical conduction network formed by the fully conductive latex nanoparticles. The addition of PTEB for EDOT polymerization significantly reduced the size of composite particles, formed stable spherical particles, enhanced thermal stability, crystallinity, and conductivity of PEDOT:PTEB composite. Evidence from UV–VIS and FTIR measurement showed that strong molecular interaction between PTEB and PEDOT resulted in the doping of PEDOT chains. X‐ray analysis further demonstrated that PTEB chains were intercalated in the layered crystal structure of PEDOT. The emulsion polymerization of EDOT using conducting surfactant, PTEB demonstrated the synergistic effect of PTEB on colloid stability and intercalation doping of PEDOT during polymerization resulting in significant conductivity improvement of PEDOT composite nanoparticles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2536–2548, 2008