Effect of the monomer ratio on the properties of poly(methyl methacrylate butyl acrylate) latex‐modified mortars

This article deals with the effect of the monomer ratio on the typical properties of polymer‐modified mortars with poly(methyl methacrylate butyl acrylate) latices. Polymer‐modified mortars, with methyl methacrylate/butyl acrylate copolymer latices of various methyl methacrylate/butyl acrylate ratios, were prepared with different polymer/cement ratios and were tested for their workability, air content, compressive strength, flexural strength, and water absorption. On the basis of the test results, the effects of the monomer ratio and polymer/cement ratio on the typical properties were examined. The properties of the latex‐modified mortars were affected to a great extent by both the monomer ratio and polymer/cement ratio. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2403–2409, 2004     

Complexation of poly(dimethylsiloxane)/poly(methyl methacrylate‐co‐butyl acrylate‐co‐methacrylic acid) latex with poly(dimethylsiloxane)/poly(vinyl acetate‐co‐butyl acrylate) latex

Two latices—the poly(dimethylsiloxane) (PDMS)/poly(methyl methacrylate‐co‐butyl acrylate‐co‐methacrylic acid) system (PA latex) and the PDMS/poly(vinyl acetate‐co‐butyl acrylate) system (PB latex)—were prepared by seeded emulsion polymerization, and PA/PB complex latices were obtained through the interparticle complexation of the PA latex with the PB latex. In addition, for the further study of the interparticle complexation of the PA latex with the PB latex, copolymer latices [PDMS/methyl methacrylate‐co‐butyl acrylate‐co‐vinyl acetate‐co‐methacrylic acid) (PC)] were prepared according to the monomer recipe of the complex latices and the polymerization process of the component latices. The properties of the obtained polymer latices and complex latices were investigated with surface‐tension, contact‐angle, and viscosity measurements. The mechanical properties of the coatings obtained from the latices were investigated with tensile‐strength measurements. The results showed that, in comparison with the two component latices (PA latex and PB latex) and the corresponding copolymer latices (PC latices), the PA/PB complex latices had lower surface tension, lower viscosities, and better wettability to different substrates. The tensile strengths of the coatings obtained from the complex latices were higher than the tensile strengths of the coatings from the two component latices and copolymer latices. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2522–2527, 2004     

Synthesis and characterization of poly(butyl acrylate)/silica and poly(butyl acrylate)/silica/poly(methyl methacrylate) composite particles

Poly(butyl acrylate)/poly(methyl methacrylate) (PBA/PMMA) core–shell particles embedded with nanometer‐sized silica particles were prepared by emulsion polymerization of butyl acrylate (BA) in the presence of silica particles preabsorbed with 2,2′‐azobis(2‐amidinopropane)dihydrochloride (AIBA) initiator and subsequent MMA emulsion polymerization in the presence of PBA/silica composite particles. The morphologies of the resulting PBA/silica and PBA/silica/PMMA composite particles were characterized, which showed that AIBA could be absorbed effectively onto silica particles when the pH of the dispersion medium was greater than the isoelectric potential point of silica. The critical amount of AIBA added to have stable dispersion of silica particles increased as the pH of the dispersion medium increased. PBA/silica composite particles prepared by in situ emulsion polymerization using silica preabsorbed with AIBA showed higher silica absorption efficiency than did the PBA/silica composite particles prepared by direct mixing of PBA latex and silica dispersion or by emulsion polymerization in which AIBA was added after the mixing of BA and silica. The PBA/silica composite particles exhibited a raspberrylike morphology, with silica particles “adhered” to the surfaces of the PBA particles, whereas the PBA/silica/PMMA composite latex particles exhibited a sandwich morphology, with silica particles mainly at the interface between the PBA core and the PMMA shell. Subsequently, the PBA/silica/PMMA composite latex obtained had a narrow particle size distribution and good dispersion stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3425–3432, 2006     

Preparation of hemispherical poly(4‐vinylpyridine‐co‐butyl acrylate)/poly(styrene‐co‐butyl acrylate) composite microspheres by seeded preswelling emulsion polymerization

Seeded preswelling emulsion polymerization was carried out by using monodispersed poly(4‐vinylpyridine‐co‐butyl acrylate) [P(4VP‐BA)] particles as the seed, and styrene and butyl acrylate as the second‐stage monomers under different polymerization conditions, to obtain hemispherical polystyrene (PST)‐rich–P4VP‐rich microspheres. Prior to polymerization, toluene was added into the preswelling system together with the second‐stage monomers. It was found that, with the increase of the amount of toluene, the particle morphology showed a tendency toward desirable hemispherical structure, and the colloidal stability of composite latex was improved. When the weight ratio of toluene/seed latex was increased up to 7.5/40 (g/g), the stable hemispherical latex could be obtained. However, when toluene was not added, the coagulum formed on the wall of the reactor during polymerization, and the composite particles with multiple surface domains (such as sandwich‐like, popcorn‐like) were formed. In addition, the final morphology of composite particles was influenced by the polarity of the seed crosslinker and the hydrophilicity of the second‐stage initiator, which could affect the mobility of poly(styrene‐co‐butyl acrylate) [P(ST‐BA)] chains. The morphology development during the polymerization was investigated in detail, and a schematic model was derived to depict the formation mechanism of hemispherical P(4VP‐BA)/P(ST‐BA) composite microspheres. The results revealed that the mobility of the P(ST‐BA) chains influenced the diffusion of the P(ST‐BA) domains on the surface of the P(4VP‐BA) matrix. When the mobility of the P(ST‐BA) chains allowed small‐size P(ST‐BA) domains to coalesce into one larger domain, complete phase‐separated morphology (hemisphere) could be achieved. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3811–3821, 2003     

Synthesis and characterization of butyl acrylate/methyl methacrylate/glycidyl methacrylate latexes

The butyl acrylate (BA)/methyl methacrylate (MMA), and glycidyl methacrylate (GMA) composite copolymer latex was synthesized by seeded emulsion polymerization technique taking poly(methyl methacrylate) (PMMA) latex as the seed. Four series of experiments were carried out by varying the ratio of BA : MMA (w/w) (i.e. 3.1 : 1, 2.3 : 1, 1.8 : 1, and 1.5 : 1) and in each series GMA content was varied from 1 to 5% (w/w). The structural properties of the copolymer were analyzed by FTIR, ¹H‐, and ¹³C‐NMR. Morphological characterization was carried out using transmission electron microscopy (TEM). In all the experiments, monomer conversion was ～99% and final copolymer composition was similar to that of feed composition. The incorporation of GMA into the copolymer chain was confirmed by ¹³C‐NMR. The glass transition temperature (T_g) of the copolymer latex obtained from the differential scanning calorimetry (DSC) curve was comparable to the values calculated theoretically. With increase in GMA content, particles having core‐shell morphology were obtained, and there was a decrease in the particle size as we go from 2–5% (w/w) of GMA. The adhesive strength of the latexes was found to be dependent on the monomer composition. With increase in BA : MMA ratio, the tackiness of the film increased while with its decrease the hardness of the film increased. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influences of the polymerization ingredients on the porous morphology of soap‐free poly(methyl methacrylate/ethyl acrylate/methacrylic acid) seeded latex particles

Monodispersed soap‐free poly(methyl methacrylate/ethyl acrylate/methacrylic acid) latex particles were synthesized by the seeded emulsion polymerization of methyl methacrylate, ethyl acrylate, and methacrylic acid (MAA), and particles with a porous morphology were obtained after an alkali posttreatment. The effects of the unsaturated acid and crosslinking agent on the properties and morphology of the latex particles were investigated. The results showed that the particle size decreased and its distribution widened when the concentration of MAA was greater than 10.0 mol % or the concentration of ethylene glycol dimethacrylate (EGDMA) was greater than 1.5%. When more than 4.0 mol % MAA was used, a porous structure could be detected clearly under a transmission electron microscope, and the particle volume and pore size first gradually increased to a maximum and then decreased rapidly with an increase in the MAA concentration. The porous morphology disappeared completely as the MAA concentration reached 16.0 mol %. A multihollow morphology was generated when the EGDMA concentration exceeded 1.0%, and the particle volume decreased monotonously with the concentration of EGDMA increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1934–1939, 2006     

Synthesis and characterization of poly(butyl acrylate–methyl methacrylate)/polyaniline core–shell latexes

Poly(butyl acrylate–methyl methacrylate) [P(BA–MMA]/polyaniline (PANI) core–shell complex particles were synthesized with a two‐step emulsion polymerization method with P(BA–MMA) as the core and PANI as the shell. The first step was to prepare P(BA–MMA) latex particles as the core via soapless emulsion polymerization. The second step was to prepare P(BA–MMA)/PANI core–shell particles. Sodium dodecyl sulfate was fed into the P(BA–MMA) emulsion as a surfactant, and this was followed by the addition of the aniline monomer. A bilayer structure of the surfactant over the surfaces of the core particles was desired so that the aniline monomer could be attracted near the outer surface of the core particles. In some cases, dodecyl benzene sulfonic acid was added after 2 h when the polymerization of aniline was started. The final product was the desired core–shell particles. The morphology of P(BA–MMA) and P(BA–MMA)/PANI particles was observed with transmission electron microscopy. The thermal properties were studied with thermogravimetric analysis and differential scanning calorimetry. Furthermore, conductive films made from the core–shell latexes were prepared, and the electrical conductivities of the films were studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 823–830, 2007     

Phase behavior of a sodium dodecanol allyl sulfosuccinic diester/n‐pentanol/methyl acrylate/butyl acrylate/water microemulsion system and preparation of acrylate latexes by microemulsion polymerization

Pseudoternary phase diagrams of quaternary microemulsion systems composed of the reactive surfactant sodium dodecanol allyl sulfosuccinic diester, n‐pentanol, methyl acrylate/butyl acrylate, and water were made. The influence of the mass ratio of sodium dodecanol allyl sulfosuccinic diester to the cosurfactant (n‐pentanol) in the system and the influence of electrolyte sodium chloride on the microemulsion area were examined. The microstructure of the microemulsion was determined with a conductance technique. The results suggested that there were three structures in the microemulsion system: water in oil, oil in water, and a bicontinuous phase. Microemulsion polymerizations were carried with some point in the microemulsion region being chosen as the formulation. The structure and configuration of the polymer latexes were determined and analyzed with Fourier transform infrared, differential scanning calorimetry, and scanning electron microscopy. The results suggested that the reactive surfactant could participate in the polymerization with the monomers to some extent; the glass‐transition temperature of the latex was ?31.4°C. The polymer latex was transformed gradually from an open porous structure to a closed porous structure when its pregnant microemulsion was varied from a bicontinuous structure to an oil‐in‐water structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and properties of alkoxysilane/butyl acrylate/methyl methacrylate copolymer latices

The incorporation of alkoxysilanes into latex systems is of major interest in the field of colloidal science. Two kinds of vinyl‐containing alkoxysilanes, methacyloxypropyltrimethoxyl silane and vinyltriethoxysilane, were copolymerized with butyl acrylate and methyl methacrylate by seeded emulsion polymerization, and copolymer latices were obtained. The morphologies of the latex particles were characterized with transmission electron microscopy. Dynamic light scattering showed that the particle size increased and the particle size distributions of all the copolymer latex particles were alike with increasing amounts of organosilane. The effects of the organosilane content on the morphology of the particles, the rheology, and the swelling properties were also investigated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of poly(butyl acrylate)‐poly(methyl methacrylate) core–shell nanomaterials of anti‐crease‐whitening properties

Core–shell nanomaterials of poly(butyl acrylate)‐poly(methyl methacrylate) were synthesized using a differential microemulsion polymerization method for being used as polyacrylate‐based optical materials, which meet the requirement of anti‐crease‐whitening and proper mechanical strength. The effects of reaction temperature and surfactant amount on the particle sizes, as well as the effect of reaction temperature on the conversion and solid content were investigated to reveal the dependence of the application properties on the reaction conditions. The spherical morphology of core–shell nanoparticles was also studied via transmission electron microscopy. The resulting polymers with a core–shell monomer ratio of butyl acrylate/methyl methacrylate at 32/10 (vol/vol) demonstrated the optimal balanced properties in the anti‐crease‐whitening and mechanical property, confirmed by the visible light transmittance measurement and the dynamic analysis of the viscoelastic properties of the synthesized core–shell nanomaterials. The smaller the particle size, the better the transparency of the resulting polymer films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39991.     

Effect of seed characteristics on morphology development in poly(n‐butyl acrylate)‐poly(n‐butyl methacrylate) core‐shell dispersions

This article reports on the influence of synthesis characteristics such as seed cross linking, particle‐size distribution (PSD), and surfactant in the seeded emulsion polymerization of n‐butyl acrylate–butyl methacrylate core‐shell systems. These systems were studied using a combination of techniques such as light scattering (static and dynamic), asymmetric field flow fractionation coupled with multiangle laser light scattering and transmission electron microscopy. Complimentary data, obtained from static light scattering and electron microscopy studies, on the effect of seed crosslinking on morphology development reveals that the presence of a crosslinked seed favors the formation of nonequilibrium core‐shell morphology. For uncrosslinked seeds occluded structures were present with a diffuse boundary between the core and the shell. In both cases, i.e., with or without surfactant, a monomodal PSD was observed for the core‐shell systems and the relative size polydispersity and the shape of the seed PSD were retained. Use of surfactant was found to broaden the PSD but did not seem to affect the formation core‐shell morphology. The study also shows the influence of crosslinked seeds on the film properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation of poly(methyl methacrylate)/titanium oxide composite particles via in‐situ emulsion polymerization

Poly(methyl methacrylate) (PMMA)/Titanium oxide (TiO₂) composite particles were prepared via in‐situ emulsion polymerization of MMA in the presence of TiO₂ particles. Before polymerization, the TiO₂ particles was modified by the silane coupling agent, which is crucial to ensure that PMMA reacts with TiO₂ via covalent bond bindings. The structure of the obtained PMMA/TiO₂ composite particles was characterized using Fourier transform infrared spectra (FTIR) and thermogravimetric analysis (TGA). The results indicate that there are covalent bond bindings between PMMA macromolecules and TiO₂ particles. Based on these facts, several factors affecting the resulting PMMA/TiO₂ composite system, such as the type of coupling agents, the mass ratio of the MMA to the modified TiO₂, the emulsifier concentration, and the initiator concentration, etc., were examined by the measurement of conversion of monomers, the gel content of polymers, the percentage of grafting, and the grafting efficiency, using gravity method or TGA method. As a result, the optimized recipe was achieved, and the percentage of grafting and the grafting efficiency could reach 216.86 and 96.64%, respectively. In addition, the obtained PMMA/TiO₂ composite particles were found to a stable colloidal dispersion in good solvent for PMMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4056–4063, 2006     

Morphology of poly(butyl acrylate)/poly(styrene‐co‐methyl methacrylate) latex prepared by starved emulsion polymerization: II. Development of particle morphology

Heterogeneous latexes were prepared by a two‐stage seeded emulsion polymerization process under monomer starved conditions at 80 °C using potassium persulfate as the initiator and sodium dodecyl sulfate as the emulsifier. Poly(butyl acrylate) latexes were used as seeds. The second‐stage polymer was poly(styrene‐co‐methyl methacrylate). By varying the amount of methyl methacrylate (MMA) in the second‐stage copolymer, the polarity of the copolymer phase could be controlled. It was found that the latex particles displayed different morphologies depending on the monomer ratio. The amount of MMA had a significant effect on the evolution of morphology. The morphologies were observed by transmission electron microscopy. In addition, the evolution of the particle morphology was predicted by the mathmatical model for cluster migration. The model gave the same trends as the experimental results. © 2002 Society of Chemical Industry     

Effect of the chain‐transfer‐agent content on the emulsion polymerization process and adhesive properties of poly(n‐butyl acrylate‐co‐acrylic acid) latexes

The effect of water on regenerated silkworm silk fibers has been studied and compared with that of water on natural silkworm silk fibers. Regenerated fibers are spun from an N‐methylmorpholine‐N‐oxide (NMMO) fibroin solution through a wet‐spinning process, leading to fibers with two distinct tensile behaviors, labeled as brittle and ductile, respectively. Regenerated fibers show a significant contraction when immersed in water. Contraction increases further after drying. In contrast, natural silkworm silk fibers show a negligible contraction when submerged in water. Regenerated fibers tested in water are considerably more compliant than samples tested in air, though their stiffness and tensile strength are significantly reduced. It has been shown that the tensile properties of brittle regenerated fibers can be modified by a wet‐stretching process, which consists of deforming the fiber while immersed in water. Regenerated wet‐stretched fibers always show a ductile behavior independent from their initial tensile behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

粒径可控的聚丙烯酸丁酯/聚甲基丙烯酸甲酯核壳乳液的制备及表征

采用种子乳液聚合法制备了聚丙烯酸丁酯(PBA)乳液,然后通过第二单体甲基丙烯酸甲酯的预溶胀法聚合制备了PBA/聚甲基丙烯酸甲酯(PMMA)乳液,用激光散射粒度仪和透射电子显微镜对乳液粒径和结构进行了表征.结果表明,当乳化剂十二烷基硫酸钠质量分数为丙烯酸丁酯的1.5%时,可制备粒径为53.6 nm且分布窄的PBA种子乳液;通过调整补加乳化剂、单体与种子乳液的用量,可制得粒径为53.6～443.8 nm的一系列单分散PBA乳液;PBA/PMMA乳液具有完善的核壳结构,且在核壳两相间存在着一个过渡层.     

Molecular weight development in emulsion copolymerization of n‐butyl acrylate and styrene

The seeded emulsion copolymerization of n‐butyl acrylate and styrene in a weight ratio of 50/50 was investigated. The effect of the type of process (batch vs. semicontinuous) and the amounts of initiator and emulsifier charged into the reactor on the time evolution of the fractional conversion, number of polymer particles, and weight‐average molecular weight (M_w) was analyzed. It was found that the M_w depends to a slight extent on the type of process and the emulsifier concentration and to a larger extent on the initiator concentration. The molecular weight distributions (MWDs) and the gel content of the final latexes were also analyzed. In the absence of chain transfer agents (CTAs), the fraction of gel was higher in the semicontinuous processes. It was also found that the gel content increased with increasing initiator concentration in the recipe. The addition of 1 wt % CTA avoided gel formation and led to an important reduction of the M_w. Nevertheless, the MWDs presented a shoulder or even a second peak at high molecular weights that was due to reactions of chain transfer to the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1918–1926, 2003     

Preparation and properties of core–shell nanosilica/poly(methyl methacrylate–butyl acrylate–2,2,2‐trifluoroethyl methacrylate) latex

A core–shell nanosilica (nano‐SiO₂)/fluorinated acrylic copolymer latex, where nano‐SiO₂ served as the core and a copolymer of butyl acrylate, methyl methacrylate, and 2,2,2‐trifluoroethyl methacrylate (TFEMA) served as the shell, was synthesized in this study by seed emulsion polymerization. The compatibility between the core and shell was enhanced by the introduction of vinyl trimethoxysilane on the surface of nano‐SiO₂. The morphology and particle size of the nano‐SiO₂/poly(methyl methacrylate–butyl acrylate–2,2,2‐trifluoroethyl methacrylate) [P(MMA–BA–TFEMA)] core–shell latex were characterized by transmission electron microscopy. The properties and surface energy of films formed by the nano‐SiO₂/P(MMA–BA–TFEMA) latex were analyzed by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy/energy‐dispersive X‐ray spectroscopy, and static contact angle measurement. The analyzed results indicate that the nano‐SiO₂/P(MMA–BA–TFEMA) latex presented uniform spherical core–shell particles about 45 nm in diameter. Favorable characteristics in the latex film and the lowest surface energy were obtained with 30 wt % TFEMA; this was due to the optimal migration of fluorine to the surface during film formation. The mechanical properties of the films were significantly improved by 1.0–1.5 wt % modified nano‐SiO₂. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011