Electroconductive performance of polypyrrole/graphene nanocomposites synthesized through in situ emulsion polymerization

The present study demonstrates a modified in situ emulsion polymerization (EP) approach convenient for the formation of polypyrrole/graphene (PPy/GN) nanocomposites with harnessed conductivities. A series of PPy/GN nanocomposites were prepared by loading different weight percent (wt %) of GN during in situ EP of pyrrole monomer. The polymerization was carried out in the presence of dodecyl benzene sulfonic acid, which acts as an emulsifier and protonating agent. The microstructures of the nanocomposites were studied by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, Fourier transform infrared, X‐ray photoelectron spectroscopy, UV–vis spectroscopy, Raman spectroscopy, photoluminescence spectroscopy and thermogravimetric analyses. The electrical conductivities of the nanocomposite pellets pressed at different applied pressures were determined using four probe analyzer. The electrical conductivities of the nanocomposites were considerably enhanced as compared to those of the individual PPy samples pressed at the same pressures. An enhanced conductivity of 717.06 S m^?1 was observed in the sample with 5 wt % GN loading and applied pressure of 8 tons. The results of the present study signify that the addition of GN in the PPy polymer harnesses both electrical and thermal properties of the polymer. Thus, PPy/GN nanocomposites with superior properties for various semiconductor applications can be obtained through direct loading of GN during the polymerization process. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41800.     

Morphology control of conducting polypyrrole nanostructures via operational conditions in the emulsion polymerization

Polypyrrole (PPy) nanostructures with diameter smaller than 100 nm were synthesized by chemical oxidative polymerization of pyrrole in the presence of cetyl trimethylammonium bromide and sodium dodecyl sulfate as surfactants. Hydrochloric acid was used as dopant, and a solution of potassium peroxydisulfate was used as initiator. The influence of polymerization temperature, feeding strategy, and the type of surfactant on the morphology and conductivity of PPy nanostructures were investigated and well‐described. A simple route just via controlling the operational conditions in the emulsion polymerization is reported to obtain nanostructured PPy with desirable morphology and relatively good conductivity. The analysis results demonstrated that the conductivity of samples is highly affected by their morphology whereas PPy nanofibers exhibited higher conductivity respecting the other morphologies (0.66 S/cm). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44697.     

Nano‐SiO2/PMMA‐PU composite particles with core‐shell structure via emulsion polymerization and their application in epoxy resin

A novel method of nano‐SiO₂/poly(methyl methacrylate)(PMMA)‐polyurethane(PU) composite particles modifying epoxy resin is reported. The composite particles with the obvious core‐shell structure were prepared by emulsion polymerization of PMMA and PU prepolymer on the surface of nano‐SiO₂. The diameter of the composite particles was 50–100 nm with dark core SiO₂ (30–60 nm) and light shell polymer of PMMA and PU (20–30 nm); moreover, PU was well distributed in PMMA with about 10 nm diameter. After nano‐SiO₂ was encapsulated by PMMA and PU, the Si content on the surface decreased rapidly to 2.08% and the N content introduced by PU was about 1.27%. The ratio of polymer to original nano‐SiO₂ (f_p), the grafting ratio of polymer to original nano‐SiO₂ (f_r) and the efficiency grafting ratio of polymer (f_e) were, respectively, about 116.7%, 104.4%, and 89.5%. The as‐prepared composite particles were an effective toughness agent to modify epoxy resin, and the impact strength of the modified epoxy resin increased to 46.64 kJ m^?2 from 19.12 kJ m^?2 of the neat epoxy resin. This research may enrich the field of inorganic nanoparticles with important advances toward the modification for polymer composite materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41919.     

种子乳液聚合制备MCPU-PMMA复合乳液

本文采用改性蓖麻油合成了软段中含不饱和双键的阴离子聚氨酯水分散液（MCPU），将其作为可聚合乳化剂和种子成分同甲基丙烯酸甲酯（MMA）进行共聚，制得了MCPU－PMMA复合乳液。1HNMR谱图显示MCPU中含有双键结构,共聚后双键消失。通过考察单体转化率和复合乳液平均粒径、凝胶量及成膜耐水及甲苯性探讨了影响种子乳液聚合的多种因素：采用过硫酸钾作为引发剂，单体转化率高，乳液粒径小，成膜耐水及甲苯性好；反应的表观活化能Ea为164.86kJ/mol，反应温度控制在70℃较适宜；聚合反应速率Rp∝［I］1.0856，引发剂用量宜控制在聚合有效组份总质量的0.5％。     

Preparation of emulsifier‐free polystyrene by conventional emulsion polymerization with a hydrolysable emulsifier

An alkali‐hydrolyzable surfactant, (1‐tetradecyloxycarbonyl)trimethylammonium chloride, was used as an emulsifier for emulsion polymerization of styrene inwater. The polymerization yielded a high molecular‐weight polymer almost quantitatively. Addition of a small amount of NaOH to the resulting latex solution precipitated the polymer immediately. Analysis of the centrifuged solid indicated almost perfection of both recovery of the polymer and removal of surface‐active species from it. Minimization of ionic species in the polymer solid was confirmed by a high contact angle of the polymer film with water. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polymer/carbon nanotube composite emulsion prepared through ultrasonically assisted in situ emulsion polymerization

In this study, ultrasonic irradiation and in situ emulsion polymerization were combined to prepare stable poly(methyl methacrylate‐co‐n‐butyl acrylate) (P(MMA‐BA))/carbon nanotubes (CNTs) composite emulsion, which solves the dispersion problem of CNTs in the latex. Two stages were adopted. In Stage I, ultrasonically initiated in situ emulsion polymerization was conducted to disperse CNTs and prepare the seed emulsion containing polymer coated CNTs. In Stage II, conventional in situ emulsion polymerization was conducted to further enhance the monomer conversion and solid content. The dispersion behavior of MWCNTs in aqueous solution under ultrasonic irradiation was investigated by spectrophotometry. The effects of CNTs content on the emulsion stability and mechanical properties of composite film were studied. The results suggest that in the composite emulsion the long CNTs with a diameter of 20–40 nm are separated and dispersed by the formed polymer latex nanoparticles with a size of 20–40 nm. The spherical polymer latex nanoparticles adhere to the wall of CNTs to form a structure like “grapes on the twig.” The smooth, uniform, and flexible polymer/CNTs composite films were prepared from the composite emulsion. The CNTs can be individually dispersed in P(MMA‐BA)/CNTs composite film. Tensile tests suggest that with the increase in the CNTs content, the Young's modulus and the yield strength of the film increase. Only at 1 wt % CNTs, the Young's modulus increases from 124 to 289 MPa, and the yield strength is improved about ～14%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3123–3130, 2006     

Synthesis and characterization of functionalized polymer latex particles through a designed semicontinuous emulsion polymerization process

Monodispersed noncarboxylated and carboxylated poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) latices were synthesized with a well‐defined semicontinuous emulsion polymerization process. A modified theory to correlate the polymerization rate to the instantaneous conversion of the monomer or comonomer mixture was developed. The resulting equation was used to determine the maximum polymerization rate only below or equal to which the polymerization could be operated in the highly monomer‐starved regime, which corresponded to an instantaneous conversion of 90% or greater. Experimental data from reaction calorimetry supported that the polymerization was under highly monomer‐starved conditions when the model latices were synthesized with the modified model. The estimation of the average number of free radicals per latex particle(n?) during the feeding stage revealed that n? was as high as 1.4 in the actual polymerization, which showed that the original selection of 0.5 as the n? value was not accurate in the developed model. From the conductimetric titration experiments, we found that most of the carboxyl groups from the methacrylic acid (MAA) were buried inside the latex particles, and the surface carboxyl group coverage increased as the MAA concentration in the comonomer feed increased. The glass‐transition temperatures of the synthesized polymers were close to the designed value from the Pochan equation, and only one glass transition was observed in the polymer samples in the differential scanning calorimetry measurements, indicating a homogeneous copolymer composition in the functionalized shell. Particle size characterization and transmission electron microscopy confirmed the uniformity in the latex particle size. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 248–256, 2005     

Synthesis of well‐defined,functionalized polymer latex particles through semicontinuous emulsion polymerization processes

The design of a semicontinuous emulsion polymerization process, primarily based on theoretical calculations, has been carried out with the objective of achieving overall independent control over the latex particle size, the monodispersity in the particle size distribution, the homogeneous copolymer composition, the concentration of functional groups (e.g., carboxyl groups), and the glass‐transition temperature with n‐butyl methacrylate/n‐butyl acrylate/methacrylic acid as a model system. The surfactant coverage on the latex particles is very important for maintaining a constant particle number throughout the feed process, and this results in the formation of monodisperse latex particles. A model has been set up to calculate the surfactant coverage from the monomer feed rate, surfactant feed rate, desired solid content, and particle size. This model also leads to an equation correlating the polymerization rate to the instantaneous conversion of the monomer or comonomer mixture. This equation can be used to determine the maximum polymerization rate, only below or at which monomer‐starved conditions can be achieved. The maximum polymerization rate provides guidance for selecting the monomer feed rate in the semicontinuous emulsion polymerization process. The glass‐transition temperature of the resulting carboxylated poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) copolymer can be adjusted through variations in the compositions of the copolymers with the linear Pochan equation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 30–41, 2003     

Poly(methyl methacrylate) nanoparticles prepared through microwave emulsion polymerization

The emulsifier‐free emulsion polymerization of methyl methacrylate (MMA) was conducted with microwave irradiation. Superfine and monodisperse poly(methyl methacrylate) (PMMA) microspheres were obtained. Microwave irradiation notably promoted the polymerization reaction. This phenomenon was ascribed to the acceleration of the initiator [potassium persulfate (KPS)] decomposition by microwave irradiation. The experimental results revealed that the apparent activation energy of KPS decomposition decreased from 128.3 to 106.0 kJ/mol with microwave irradiation. The average particle size of the prepared PMMA latex was mainly controlled with the MMA concentration; it increased linearly from 103 to 215 nm when the MMA concentration increased from 0 to 0.3 mol/L and then remained almost constant at MMA concentrations of 0.3–1.0 mol/L. The KPS concentration had no effect on the average particle size, but the particle size dispersity was significantly reduced by a high KPS concentration. With a mixed polymerization phase (water/acetone = 1:3 v/v) or a redox initiation system, PMMA nanoparticles were obtained with an average particle size of 45 or 67 nm, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2815–2820, 2004     

Ionic liquid as surfactant in microwave‐assisted emulsion polymerization

The aim of this work is to study the use of an ionic liquid (IL) as surfactant in emulsion polymerization reactions and to evaluate its effect when these reactions are heated under microwave irradiation. The IL 1‐n‐dodecyl‐3‐methylimidazolium chloride was chosen to replace the surfactant dodecyltrimethylammonium bromide (DTAB) in methyl methacrylate emulsion polymerizations. The conversion evolutions and the final average diameter of polymeric particles were quite similar for reactions using the surfactant DTAB or the IL, showing that the IL acted efficiently as surfactant in emulsion polymerizations. Comparing the polymerization reactions performed under microwave irradiation and conventional heating, reaction rate enhancements were obtained for both DTAB and IL. Using a pulsed scheme, under high‐power microwave irradiation, slightly higher reaction rates and molecular weights were obtained in reactions using IL, in comparison with surfactant DTAB, indicating the existence of some specific effects linked to IL–microwaves interaction. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Novel hydrophilic N-halamine polymer with enhanced antibacterial activity synthesized by inverse emulsion polymerization

N-halamine-based antibacterial agents have high efficiency and rechargeable antibacterial properties. However, their applications are limited due to their complex synthetic process and fuzzy antibacterial mechanism. In this study, a novel N-halamine antibacterial polymer was synthesized by inverse emulsion polymerization and characterized by Fourier transform infrared, nuclear magnetic resonance, scanning electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. Due to the difficulty of purification, most of the subjects studied previously were hydrophobic polymers, while little research on hydrophilic polymers. In this experiment, this difficulty was overcome by controlling the dosage of sodium hypochlorite and methods of dialysis. Because of the complex cell structure of Gram-negative bacteria, it is difficult for N-halamines to release the oxidizing chlorine into the cell. However, the hydrophilic N-halamines can solve this problem, which showed a stronger antibacterial effect on Gram-negative Escherichia coli synthesized in this study. In addition, the particle size and hydrophilic property of the polymer were changed by changing the amount of initiator, and the differences in their antibacterial properties were studied. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47419.     

Synthesis of stable high hydroxyl content self‐emulsifying waterborne polyacrylate emulsion

The stability of hydroxyl polyacrylate emulsion was studied from two aspects of the structure of latex particles and polymerization conditions. Waterborne polyacrylate was prepared through seeded semicontinuous emulsion polymerization method with pre‐emulsification process. HEMA was used to provide a high content of hydroxyl group, and the reactive emulsifier SE‐10 was introduced to substitute for the traditional emulsifier. The best conditions including polymerization process and temperature, monomer types and dropping time were determined, and the effects of emulsifier content and addition method, HEMA content, chain transfer agent content, and soft/hard monomer ratio on the properties of emulsion were investigated. Through the optimization of polymerization conditions and the control of the structure of particles, we have successfully synthesized the core‐shell structure of polyacrylate emulsion with a good appearance, low viscosity and a solid content of 46.5%. The hydroxyl polyacrylate exhibits good performance, which has great potential in development and application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44844.     

Lamotrigine‐loaded polyacrylate nanoparticles synthesized through emulsion polymerization

A series of copolymeric nanoparticles of the partially water‐soluble monomer ethyl methacrylate and the water‐soluble monomer 2‐hydroxyl ethyl methacrylate were synthesized from emulsions containing sodium dodecyl sulfate via free‐radical polymerization. Lamotrigine, as a model drug, was loaded in nanoparticles during in situ polymerization. A stable and transparent poly(ethyl methacrylate‐co‐hydroxyl ethyl methacrylate) nanolatex was produced for all compositions and characterized for particle size by dynamic light scattering and transmission electron microscopy. Particles were found to be smaller than 50 nm in size. Structural characterization of copolymers was done by infrared spectrometry, gel permeation chromatography, and NMR spectroscopy. Drug encapsulation efficiency was determined by ultraviolet (UV)–visible spectrometry and was found to be 26–62% for copolymers with different compositions. UV data suggest molecular‐level dispersion of the drug in the nanoparticles. In vitro drug‐release studies showed the controlled release of lamotrigine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Core–shell emulsion polymerization of styrene and butyl acrylate in the presence of polymerizable emulsifier

A series of core–shell polymeric particles of styrene butyl acrylate were successfully prepared in the presence of polymerizable emulsifier. The compositions of the emulsions obtained were confirmed by Fourier transformed infrared spectrometry. Latexes and emulsion films were characterized by transmission electron microscopy and scanning electron microscopy, respectively. The thermostability of emulsion films was characterized by thermogravimetric analysis. The results showed that the existence of polymerizable emulsifier could enhance the solid content of the emulsion and the monomer conversion. The optimum mass ratio of polymerizable emulsifier to traditional emulsifier was 1:1, and the polymerizable emulsifier can participate in the emulsion polymerization perfectly. An emulsion with reverse core–shell particles exhibited better hydrophobic properties and thermostability than one with traditional core–shell particles. The film formed by the emulsion with reverse core–shell particles had lower water absorption, and it could be used in the fields of coatings, surface sizing agents, and spinning. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43091.     

乳液聚合方法研究进展

乳液聚合方法具有各方面的优点和广泛的应用范围,因此,受到人们的广泛关注。本文介绍了乳液聚合的优缺点,并着重介绍了一些新的乳液聚合方法及其原理、特点、应用以及中外最新的一些研究成果。     

Synthesis of polyaniline nanofiber and copolymerization with acrylate through in situ emulsion polymerization

Polyaniline (PANI) was prepared, respectively, by direct mixed oxidation method in different acids. Scanning electron microscopy showed that high quality of PANI nanofibers can be obtained easily in hydrochloric acid, sulfuric acid, and acetic acid, especially in the sulfuric acid; infrared and ultraviolet spectra characterization showed all products were the doped PANI. Then, using complex emulsifiers, PANI was dispersed in acrylate emulsion by supersonic dispersion assisted with mechanical stirred to obtain mixed pre‐emulsion, the result showed different PANI performed different dispersing stability in the pre‐emulsion. More importantly, PANI–polyacrylate copolymer was prepared through multi‐steps in situ emulsion polymerization using water‐soluble azo (VA‐044) as initiator. Experiment showed that good dispersing stability of PANI in the pre‐emulsion was premise to obtain the final stable copolymer emulsion. Further, the micro‐morphology and thermal property of the copolymer were studied by transmission electron microscopy, differential scanning calorimetry, and thermogravimetric analyzer. The result proved that acrylate occurred in situ polymerization on surface of PANI nanofibers, the presence of PANI increased glass transition temperature (T_g) and thermal decomposed temperature of the copolymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of a novel polymerizable surfactant and its application in the emulsion polymerization of vinyl acetate,butyl acrylate,Veova 10, and hexafluorobutyl methacrylate

A novel anionic, polymerizable fumaric surfactant (surfmer) was synthesized. The chemical structure of the surfactant was confirmed with ¹H‐NMR, IR, and mass spectrometry. The surfmer was then used with constant addition profiles in the semicontinuous polymerization of vinyl acetate, butyl acrylate, Veova 10, and hexafluorobutyl methacrylate. The particle size, amount of coagulum, and stability against electrolytes and freezing/thawing were evaluated. Films were cast from latices; then, photographs were taken of the films after immersion in water for days, and the water adsorption was assessed. As a reference, an unreactive surfactant (sodium dodecyl sulfate) was also used for the polymerization. Compared with sodium dodecyl sulfate, the surfmer behaved much better with respect to the stability of the latices and the water sensitivity of the films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

乳液法制备聚合物纳米粒子的研究进展

综述了乳液法制备聚合物纳米粒子的研究进展,详细介绍了采用新型乳化剂,即高分子表面活性剂与反应性表面活性剂,和以超声波辐照技术为主的新技术制备聚合物纳米粒子方面的研究成果。     

Methacrylic acid-based amphiphilic block-random copolymer stabilizers for emulsion polymerization

The emulsion polymerization of styrene was investigated using polystyrene-b-[polystyrene-r-poly(methacrylic acid)] amphiphilic block-random copolymers (BRCs) of different compositions as stabilizers. These stabilizers with molar masses <20,000 g/mol, which possess unique dispersion behaviour (i.e., self-assembly with low aggregation numbers) when dissolved in aqueous medium at alkaline pH, were prepared by the nitroxide-mediated bulk polymerization of styrene to achieve a desired molar mass followed by chain extension by batchwise addition of styrene and methacrylic acid monomers to obtain the stabilizing group. Emulsion polymerizations of styrene stabilized by these BRCs yielded stable latexes with particle diameters that range between 30 and 150 nm. When different concentrations of the stabilizer (2–3.5 mM) were utilized for emulsion polymerization of styrene, a similar novel emulsion polymerization mechanism observed previously by our group for the acrylic-acid based amphiphilic BRCs was also seen, further validating the difference between this class of polymeric surfactants and conventional small molecule surfactants, block copolymers, or alkali soluble resins. The performance of methacrylic-acid based BRCs was more efficient and yielded higher surface coverage of the polystyrene latexes when compared to the acrylic-acid based BRCs as a result of the more hydrophobic nature of the former.     

Core‐shell latex synthesized by emulsion polymerization using an alkali‐soluble resin as sole surfactant

A series of alkali‐soluble resins were prepared from esterification reaction of styrene‐maleic anhydride copolymer (SMA) and four fatty alcohols having different alkyl chains. The critical aggregates concentration of the prepared hemiester was lower than SMA, indicating that modification of SMA resin with long alkyl chains could improve their emulsification efficiency. The detailed experiments of emulsion polymerization of methyl methacrylate and butyl acrylate using these hemiesters as sole surfactants showed that SMA‐C12‐75, SMA‐C14‐70, and SMA‐C16‐65 were good surfactants. In the end, we successfully prepared stable latexes using above three good surfactants with relatively low surfactant concentration and high solid content. Characterization of latexes by Zetasizer and transmission electron microscopy revealed that particles of these latexes have core‐shell nanostructure with average particle size below 60 nm. Compared with SMA, the improvement of emulsification efficiency of its hemiesters may come from the better hydrophilic‐lipophilic balance and steric stabilization after incorporation of long alkyl chain. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013