Surface modification of monolithic PolyHIPE Polymers for anionic functionality and their ion exchange behavior

Monolithic PolyHIPE Polymer (PHP), being a highly porous, low density, open cellular material was produced by polymerization of a high internal phase emulsion (HIPE) in which the polymerizable continuous phase consisted of monomers, styrene (STY), and divinyl benzene (DVB). The inner dispersed phase (90 vol %) was an aqueous solution containing 0.4 wt % potassium persulphate as initiator. The resulting porous structure had 12% crosslinking density. Surface chemistry of the monoliths was modified by chloromethylation and amination to impart anionic functionality. Surface modified monoliths had ion exchange capacity of 3.01 meq/g, and had the ability to uptake water about 10 times of its mass. It was used Cr (VI) ion removal from aqueous solution. The experimental results investigated for both the Langmuir and the Dubinin–Radushkevich adsorption models. The maximum Cr (VI) adsorptions are 126.6 mg Cr (VI)/g and 129.3 mg Cr (VI)/g, respectively. The mean free energy E of adsorption is 11.18 kJ/mol according to the Dubinin–Radushkevich adsorption model, indicating that the adsorption occurs through a chemical ion‐exchange process and it is not diffusion limited. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42286.     

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     

Preparation and properties of core [poly(styrene‐n‐butyl acrylate)]–shell [poly(styrene–methyl methacrylate–vinyl triethoxide silane)] structured latex particles with self‐crosslinking characteristics

Structured latex particles with a slightly crosslinked poly(styrene‐n‐butyl acrylate) (PSB) core and a poly(styrene–methacrylate–vinyl triethoxide silane) (PSMV) shell were prepared by seed emulsion polymerization, and the latex particle structures were investigated with Fourier transform infrared, thermogravimetric analysis, differential scanning calorimetry, transmission electron microscopy, and dynamic light scattering. The films that were formed from the structured core (PSB)–shell (PSMV) particles under ambient conditions had good water repellency and good tensile strength in comparison with films from structured core (PSB)–shell [poly(styrene–methyl methyacrylate)] latex particles; this was attributed to the self‐crosslinking of CH₂?CH? Si(OCH₂CH₃)₃ in the outer shell structure. The relationship between the particle structure and the film properties was also investigated in this work. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1824–1830, 2006     

Kinetic investigations of acrylic–polyurethane composite latex

The effect of various reaction parameters on the rate of polymerization, R_p, and on the particle size and morphology of aqueous acrylic–polyurethane hybrid dispersions, prepared by semibatch emulsion polymerization, was investigated. The particles of polyurethane dispersion were used as seeds during the polymerization of acrylic component: methyl methacrylate (MMA), butyl acrylate (BA), and a mixture of MMA and BA with the ratio of 1:1. These emulsions were found to form structured polymer particles in aqueous media using scanning electron microscopy. The kinetics of the emulsion polymerization was studied on the basis of Wessling's model. The influence of emulsifier and initiator concentrations, including the monomer feed rates, R_m, on the rates of polymerization and on the properties of the resulting dispersions were studied. The number of particles and the particle size were also measured during the polymerization process. The final values were found to be independent of the concentration of the emulsifier, initiator and the monomer feed rate in monomer starved conditions. In the steady‐state conditions, during the seeded semibatch hybrid emulsion polymerization, the rate of polymerization and the monomer feed rate followed the Wessling relationship 1/R_p = 1/K + 1/R_m. The dispersions MMA/PU, BA/PU, and MMA/BA/PU have K values of 0.0441, 0.0419 and 0.0436 mol/min, respectively. The seeded BA/PU hybrid polymerization proceeded according to Smith‐Ewart Case I kinetics, while the MMA/PU hybrid emulsions demonstrate Case II of the Smith‐Ewart kinetic model. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2639–2649, 2002     

Encapsulation of magnetic particles via miniemulsion polymerization of styrene. II. Effect of some parameters on the polymerization of styrene

Effects of some parameters on the polymerization of Styrene (St) during encapsulation of iron oxide particles via miniemulsion polymerization have been investigated. At the early stage of reaction, polymerization rate increased slightly with the increase of sonicating time, and then it leveled off. The polymerization rate increased with the increase of KPS at the early stage of polymerization, which tendency is analogous to the result of polymerization of St in miniemulsion without the presence of iron oxide particles. The increase of iron oxide not only decreased the polymerization rate but also resulted in poorer monodisperse of the particles when keeping the amount of dispersant constant. The dispersant played an important role in the encapsulation of magnetic particles via miniemulsion polymerization of St. It not only made the iron oxide disperse well in monomer droplets but also led to a much faster polymerization than that of no dispersant in system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation of monodispersed hollow polymer particles by seeded emulsion polymerization under low emulsifier conditions

In a low emulsifier system, the MMA‐BA‐MAA copolymer emulsions were prepared as seed latices and the seeded emulsion polymerization of MMA‐MAA‐DVB was consequently carried out to prepare carboxylated core particles. The hydrophobic shell was then synthesized onto the core using styrene, acrylonitrile, and divinylbenzene as comonomers. The hollow latex particles were obtained by alkalization treatment of the core‐shell latex particles. The effects of the feeding rate of monomer mixture, contents of emulsifier SDBS and crosslinking agent DVB, and ratio of the monomers during the core stage and shell stage on the morphology and volume expansion of the latex particles were investigated. The results show that the monodispersed hollow latex particles with large size can be obtained when the feeding rate is 0.1 g/min, SDBS content is 0.15 and 0.2 wt % during the core stage and shell stage, respectively, DVB contents are 1% during the preparation of shell copolymers, and the monomer ratio of the core particle to shell layer is 1 : 8. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1505–1510, 2005     

Simple method of related sensitivity range to predict the thermodynamic equilibrium morphology of a core–shell latex particle

The equilibrium morphologies of different core–shell latices are predicted, and a related sensitivity analysis is given for the predictions. This article proposes a related sensitivity range for estimating the accuracy of predictions, made with the simple method, of the thermodynamically preferred morphology of a core–shell latex particle in two‐stage seeded emulsion polymerization. The related sensitivity range of the predictions is defined and calculated, and the results show that different core–shell latices have different sensitivity ranges. The wider the sensitivity range is, the more reliable the prediction is of the morphology of the core–shell latex. The simple method of related sensitivity range has been verified in the literature and with experiments. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3144–3152, 2004     

室温可自成膜中空微粒乳液的制备

采用羧基单体进行多阶段的种子乳液聚合,制备了内核为带羧基的聚合物、最外层为易成膜的低玻璃化温度聚合物、中间为轻度交联中间隔离层的多层核壳结构乳胶粒,最后通过碱处理制成了具有室温成膜性的中空结构聚合物微粒。研究表明,在反应前期以十二烷基苯磺酸钠为乳化剂,包壳阶段同时加入OP-10可有效控制乳胶粒结构形态,同时提高聚合物乳液的电解质稳定性;以甲基丙烯酸为羧基单体,其用量为核单体总量的30%(质量分数)时,聚合物微粒中空直径较大且微粒结构规整;碱处理温度以100℃为宜。在优化的工艺下,制得的室温可成膜中空聚合物微粒外径约500 nm,中空直径约300 nm。     

中空聚合物乳胶粒子的制备

研究了在制备中空乳胶粒子的过程中,复合乳液（苯乙烯（Ｓｔ）－丙烯酸丁酯（ＢＡ）－甲基丙烯醛（ＭＡ））进行种子聚合时,Ｓｔ／ＢＡ的质量比和ＭＡ的用量对胶乳粒子的空径、粒径和表面羧基质量摩尔浓度的影响。实验结果表明,当Ｓｔ／ＢＡ的质量比为１９,ＭＡ质量分数为单体的５．６％时,形成的乳胶粒子的空径最大。     

Preparation of core‐shell latexes for paper coatings

Novel core‐shell latices with a partially crosslinked hydrophilic polymer core and a hard hydrophobic shell of polystyrene were prepared to improve optical properties of coated paper such as gloss and brightness. These core‐shell latices were prepared by sequential addition of a monomer mixture of styrene, n‐butylacrylate and methacrylic acid. Different crosslinkers were used to form the polymer core and in the second stage styrene to form the hard shell component. In addition, attempts were made to further improve optical properties by introducing a new polymerizable optical brightener, i.e., 1‐[(4‐vinylphenoxy)methyl]‐4‐(2‐phenylethylenyl)benzene during polymerization either into the core or into the shell. The prepared core‐shell latex particles were used as specialty plastic pigments for paper coating together with kaolin as the primary pigment. The runability of paper coating formulation by either using a laboratory scale Helicoater or pilot scale JET‐coating machine was very good. The produced coated papers were printed on both sides employing a heat set web offset (HSWO) printer to study the quality of image reproduction in terms of print gloss, print mottle, print through, etc. The core‐shell latices improved the overall print quality. Furthermore, the results demonstrated that by optimizing polymer composition one can significantly enhance the optical properties and surface smoothness of coated paper. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of spherical nanocomposites consisting of silica core and polyacrylate shell by emulsion polymerization

Nanocomposite particles consisting of silica (inorganic core) and polyacrylate (organic shell) were prepared in a form of emulsion by a new and simple method—the emulsion polymerization of acrylic monomers in the presence of silica sol. The key technique of the present emulsion polymerization, which made the formation of the nanocomposites successful, is the usage of nonionic surfactant above its cloud point. The morphology of the composite was investigated by DLS, AFM, and TEM, which clearly showed formation of the core‐shell‐type particles. A transparent film was prepared by casting the emulsion, which showed high resistibility against organic solvents. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 659–669, 2006     

Synthesis and characterization of PNIPAM/PS core/shell particles

Crosslinked, monodisperse PNIPAM particles were synthesized by precipitation polymerization. The particle size was measured by dynamic light scattering (DLS), capillary hydrodynamic fractionation (CHDF), and transmission electron microscopy (TEM). Two different polymerization methods were used to prepare PNIPAM/PS core/shell particles, both above and below the volume phase transition temperature (VPPT) using either a semibatch or seeded semibatch polymerization process. In both processes, uniform “raspberry” structures were obtained in which polystyrene formed small domains on the surface of the PNIPAM particles. The resulting core and shell structure was confirmed by temperature‐dependent particle size and density gradient experiments. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

Emulsifier‐free emulsion polymerization of acrylonitrile in the presence of poly(methyl methacrylate) seed particles: Influence of the addition mode on the surface morphology

Acrylonitrile (AN) was polymerized in the presence of poly(methyl methacrylate) (PMMA) seed latex by both the batch and dropwise addition modes. The two addition modes both led to PMMA/polyacrylonitrile (PAN) composite particles with a core/shell structure with PMMA as the core and PAN as the shell. The shell thickness could be adjusted by a change in the amount of the second‐stage AN monomer relative to the PMMA seed polymer. However, the surface morphologies of the composite polymers were quite different, which showed a rambutan‐like batch mode and an urchinlike dropwise mode. The reason was considered as the different precipitation mechanisms of PAN small‐particle precipitation for the batch mode and linear PAN segment growth for the dropwise mode. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

种子聚合法制备PS/PAA核壳微球的研究

设计制备了以疏水性聚苯乙烯(PS)为核、以亲水性聚丙烯酸(PAA)为壳的PS/PAA核壳结构复合微球。首先利用无皂乳液聚合法制备了亚微米级的PS微球,再以其为种子,利用种子无皂乳液聚合法制备PS/PAA核壳微球。在种子聚合阶段,选用AIBN当引发剂,经过红外光谱(IR)表征,表明当使用油溶性引发剂偶氮二异丁腈(AIBN),使其最终形成PS/PAA核壳结构微球。这种方法解决了亲水性较强的单体在以水为介质时在PS微球溶于少量的苯乙烯(St),并在引发聚合之前经过充分的吸附溶胀,可使亲水性单体AAc在PS种子微球表面聚合生成壳层,解决表面不容易直接聚合生成壳层的问题。     

核／壳型可遮盖聚合物乳液的研制

采用了种子乳液聚合法,以可被碱溶胀的丙烯酸类聚合物为核,交联型的丙烯酸类高聚物为壳,合成了新型的可以代替部分钛白粉等颜料的可遮盖聚合物。讨论了乳化剂、单体、核壳比等对聚合物性能的影响,其中核壳比在1:15-1:25时,聚合物具有较好的遮盖效果。     

Preparation of multinuclear microparticles using a polymerization in emulsion process

A new microencapsulation method, in which a paraffin medium and small sub‐micron spheres were encapsulated by an amino resin has been established. These multinuclear microparticles were made by polymerization in emulsion and characterized by scanning electron microscopy and interfacial tension measurements. This process is based on several emulsion mixings following Torza and Mason's approach, in which we combined the characteristics of a coacervation with a conventional interfacial reaction and an in situ polymerization followed by a water in oil in water emulsion. The inner phase of the microcapsules consisted of a mixture of paraffin and microspheres of poly(vinyl) alcohol/hydrated salt crosslinked by methylene diisocyanate. The encapsulation mechanism is based on the liquid/solid–liquid separation of methoxylolmelamines and will be described in this study to explain the surface morphology. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Preparation and characterization of trilayer core–shell polysilsesquioxane–fluoroacrylate copolymer composite emulsion particles

Polysilsesquioxane–fluoroacrylate copolymer [poly(methyl methacrylate)–butyl acrylate–dodecafluoroheptyl methacrylate)] (FPSQ) composite latex particles with a trilayer core–shell morphology were manufactured by seeded emulsion polymerization, where PSQ latex particles bearing reactive methacryloxypropyl moieties were first produced by the hydrolysis‐condensation of (3‐methacryloxypropyl)trimethoxysilane, and then they were utilized as seeds, with methyl methacrylate, butyl acrylate, and dodecafluoroheptyl methacrylate as the inner and outer shell monomers. Fourier‐transform infrared spectra and ¹H‐NMR confirm the structure of the FPSQs. Transmission electron microscopy and scanning electron microscopy demonstrate that the obtained composite emulsion particles emerge with the trilayer core–shell pattern. Due to the anchoring of PSQ nanoparticles, the thermal stabilities of the FPSQ films are strengthened, and the resistance to heat is gradually improved along with the increase of the fluoroacrylate dose in the polymer matrix composite. X‐ray photoelectron spectroscopy, atomic force microscopy (AFM), and hydrophobicity investigations indicate that the fluorinated chain segments tend to concentrate at the film–air two‐phase interface. In addition, the AFM result denotes that importing more fluorine into the FPSQ hybrid material will engender greater phase separation and enrichment of the fluoroalkyl segments and a rougher morphology. Thus, the water contact angle of the FPSQ film can ultimately reach 121.4°. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44845.