Preparation of flexible polyhedral particles via concentrated emulsion templating polymerization

This paper presents recent efforts on the preparation of flexible polyhedral particles via concentrated emulsion templating polymerization in which the hydrophilic monomer (acrylamide) and hydrophobic monomer (butyl acrylate) are polymerized simultaneously in the continuous and dispersed phase, respectively. Such templating polymerization has been enhanced in our systems owing to the introduction of acrylamide monomer and their higher polymerization rate in continuous phase as compared with butyl acrylate in dispersed phase. Diffusion between the different phases was also inhibited. Furthermore, the stability of the concentrated emulsion and the molecular weight of the produced poly(butyl acrylate) were found to be significantly affected by the amount of redox initiator. The morphology of the particles could be controlled by varying the volume fraction of the dispersed phase and the polyhedral particles were achieved at higher volume fraction. Copyright © 2005 Society of Chemical Industry     

Modeling the emulsion polymerization of amino-functionalized latex particles

A mathematical model for a semicontinuous seeded cationic emulsion polymerization was developed. The model includes the most distinctive features of the copolymerization of a cationic hydrophilic monomer with a hydrophobic one, including polymerization of the hydrophilic monomer in the outer shell of polymer particles and in the aqueous phase, and the possibility of having radical concentration profiles in the polymer particles.The reactions were carried out by means of a semicontinuous seeded cationic emulsion polymerization under starved conditions for styrene, which was the main monomer employed.The model predicts the evolution of the fractional overall conversions, the thickness of the outer shell, the total surface charge density and the partial conversions for the semicontinuous seeded cationic emulsion polymerization of styrene and aminoethyl methacrylate hydrochloride. Furthermore, the model can distinguish between the surface charge density provided by the cationic monomer than that given by the cationic initiator. Therefore, this model can predict the best conditions to obtain well-defined latexes with specific amounts of surface amino and amidine groups useful for immunoassays.     

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。     

Polystyrene latex synthesized in presence of ultrasonic initiation

The low water solubility of styrene (St) monomer increase the need for a good initiator system to speed up the emulsion polymerization and remove unreacted monomers. Polymerization of styrene monomer in water was performed at 30, 50, and 70°C under ultrasonic irradiation using sodium dodecyl sulfate as surfactant and ammonium persulfate as initiator. Ultrasonic energy was used as a tool to speed up the polymerization. Combining ultrasonic and ammonium persulfate led to a higher conversion and higher rate of polymerization. Ultrasonic energy has an effect on the particle size distribution. The particle size distribution increases with an increase in the monomer conversion of styrene for ultrasonic polymerization, whereas the particle size distribution did not change with an increase in the monomer conversion compared with the conventional thermal polymerization results. Higher molecular weights were obtained under ultrasonic irradiation. FE‐SEM and TEM pictures show different morphology with changing temperature polymerization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

新型核-壳结构醋丙乳液的合成及性能

采用2阶段方法合成了高亲水单体含量的核-壳结构醋丙乳液,第1阶段以水溶性引发剂过硫酸钾为引发剂合成了核,第2阶段以油溶性引发剂偶氮二异丁腈在核表面引发聚合成壳。并对乳液形貌、结构及膜的性能进行了表征。结果表明,该法合成的乳液具有凝胶率低、稳定、力学性能好等特点。     

聚苯乙烯纳米微球合成工艺研究

以苯乙烯(St)为单体,十二烷基硫酸钠为乳化剂、过硫酸钾为引发剂,碳酸氢钠和氢氧化钠为复合缓冲剂,通过乳液聚合反应,合成了粒径分布均匀的聚苯乙烯纳米微球(PSt)。在确定缓冲剂用量及引发剂滴加方式的条件下,经正交实验优选出最佳合成工艺条件如下:蒸馏水与苯乙烯的体积比为1.5:1、乳化剂用量为苯乙烯质量的1.0%、引发剂用量为苯乙烯质量的1.2%、反应时间为8h,反应温度为80℃。在此条件下转化率为94.58%,并用扫描电镜(SEM)和红外光谱(FTIR)对其进行了表征。     

Preparation of polystyrene/poly(methyl methacrylate) core‐shell composite particles by suspension‐emulsion combined polymerization

Suspension‐emulsion combined polymerization process, in which methyl methacrylate (MMA) emulsion polymerization constituents (EPC) were drop wise added to styrene (St) suspension polymerization system, was applied to prepare polystyrene/poly(methyl methacrylate) (PS/PMMA) composite particles. The influences of the feeding condition and the composition of EPC on the particle feature of the resulting composite polymer particles were investigated. It was found that PS/PMMA core‐shell composite particles with a narrow particle size distribution and a great size would be formed when the EPC was added at the viscous energy dominated particle formation stage of St suspension polymerization with a suitable feeding rate, whereas St‐MMA copolymer particles or PS/PMMA composite particles with imperfect core‐shell structure would be formed when the EPC was added at the earlier or later stage of St suspension polymerization, respectively. It was also showed that the EPC composition affected the composite particles formation process. The individual latex particles would exist in the final product when the concentrations of MMA monomer, sodium dodecyl sulfate emulsifier, and potassium persulfate initiator were great in the EPC. Considering the feature of St suspension polymerization and the morphology of PS/PMMA composite particles, the formation mechanism of PS/PMMA particles with core‐shell structure was proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

疏水缔合型两性聚丙烯酰胺增稠剂的制备及性能研究

以司班-80、OP-10为复配乳化体系,N,N′-亚甲基双丙烯酰胺(甲叉)为交联剂,丙烯酸十八酯(ODA)为长碳链疏水单体,用过硫酸钾引发丙烯酰胺(AM)、丙烯酸(AA)、甲基丙烯酰氧乙基三甲基氯化铵(DMC)进行反相乳液聚合,制备了疏水缔合型两性增稠剂。探讨了增稠剂的交联结构、交联剂用量、长碳链疏水单体用量,DMC用量以及所得产品的耐盐性、流变性和耐稀释性。结果表明:当交联剂占单体量0.17%,长链疏水单体为0.6%,DMC为13.8%时,其综合增稠效果最佳。     

A Mathematical Approach to the Analysis of Swollen Emulsion Polymerization of Styrene

A mathematical model for swollen emulsion polymerization of styrene was derived in this study. The experimental data were obtained using two different swelling agents: cetyl alcohol and lauryl alcohol. In the studied system, potassium persulfate and sodium dodecyl sulfate were used as initiator and emulsifier, respectively. The variation of total monomer conversion with the polymerization time obtained with different swelling agent-emulsifier combinations and data from SEM photographs of the final latexes were evaluated for estimation of the model parameters. In the mathematical model, it was assumed that the polymerization takes place according to first-order kinetics, within the forming latex particles in the presence of monomer diffusion from the monomer droplets to the forming latex particles. The kinetic rate constants and the variation of effective diffusion coefficient of monomer with the polymerization time were estimated using model expressions. Relative rate factor-Thiele modulus diagrams were derived for swollen emulsion polymerization system.     

苯乙烯-对氯甲基苯乙烯共聚物胶乳微球的制备及表征

以苯乙烯（St）和对氯甲基苯乙烯（VBC）为共聚单体,过硫酸钾（KPS）为引发剂,十二烷基苯磺酸钠（SDBS）为乳化剂,采用乳液聚合法制备了富含氯甲基的苯乙烯-对氯甲基苯乙烯共聚物功能微球。采用红外光谱（FT-IR）、扫描电镜（SEM）、激光粒度仪和X射线光电子能谱（XPS）对样品进行表征,研究了乳化剂用量、单体用量、引发剂用量、反应时间、反应温度等因素对微球粒径、乳液转化率的影响。结果表明,产物微球粒径均一,表面光滑、富含氯甲基功能基团,采用此方法可以制备粒径在100～250 nm的功能高分子微球。     

Modeling evidence in support of coagulative nucleation theory

An extensive lumped model was developed for emulsion polymerization. It incorporated all of the complex processes: aqueous‐phase radical balances for all radical species arising from initiator decomposition and from exit; determination of radical number inside the particles by balance among rates of radical entry into, exit from, and termination inside the particles; determination of the monomer concentration inside the particles and in the aqueous phase by a thermodynamic equation; and particle formation by micellar, homogeneous, and coagulative nucleation. Model validation was done for the system with styrene (monomer), potassium persulfate (initiator), and sodium dodeceyl sulfate (emulsifier) and for the variables, which included the duration of nucleation, conversion at the end of nucleation, and total number of particles formed. The validation process revealed that coagulation during nucleation needed to be included in the model, even for emulsifier concentrations above the critical micelle concentration. The model predictions were in good quantitative agreement with the experimental data. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

A new concentrated emulsion polymerization pathway

To ensure the stability of the concentrated emulsions that are employed as precursors for polymerization, a two-step concentrated emulsion polymerization pathway is described. In the first step, the monomer is partially polymerized by heating at 50°C until a certain conversion is reached. Subsequently, the partially polymerized monomer is used as the dispersed phase to prepare a concentrated emulsion in which water constitutes the continuous phase. The concentrated emulsion has a large volume fraction of the dispersed phase (0.74–0.99) and the appearance of a gel. Several typical monomers are employed to correlate the stability of the concentrated emulsion and the extent of partial polymerization of the dispersed phase. It was found that monomers, which cannot lead to stable concentrated emulsions, can generate them after partial polymerization. Subsequent polymerization of the concentrated emulsion leads to latex particles. Copolymers and polymer composites were also prepared by the two-step procedure. In the latter case, water was replaced with a solution of a hydrophilic monomer in water as the continuous phase. © 1992 John Wiley & Sons, Inc.     

A study of the soap-free emulsion polymerization of styrene

A study on the soap-free emulsion polymerization of styrene has been accomplished in this work. The polymerization reaction was carried out in a batch reactor under isothermal condition. Potassium persulfate was used as an initiator. In our experiments, the effects of agitation speed, monomer concentration, and initiator concentration on the number and size of polymer particles, on the conversion of monomer and molecular weight of polymers were investigated. In addition, the systems in the presence of emulsifier or CaSO₃ were investigated and discussed in comparison with a system free of them.     

Morphology development in polychloroprene–polystyrene latex interpenetrating polymer networks

Latex interpenetrating polymer networks (LIPNs) have been prepared using a crosslinked polychloroprene latex as the seed emulsion, followed by the in situ polymerization of styrene, typically with a 10% divinyl benzene crosslinker. Polychloroprene–crosslinked polystyrene (XPS) ratios ranging from 70/30 to 40/60 were used, with the second monomer being added as a single aliquot rather than by “starvation” routes. The majority of the work has been conducted using the water‐soluble persulfate initiator method, which entails lengthy (∼ 6 h) polymerizations. To follow the development of microstructure, polymerizations were also stopped at 0.5, 1, and thence hourly intervals up to 6 h, so that any effect of time on shell and domains could be seen by transmission electron microscopy (TEM). Parallel studies using azo‐bis(isobutyronitrile) (AIBN) as initiator at the same temperature were conducted. Products were also studied, after staining, by TEM. For the persulfate initiator, domain structures predominated for the 70/30 ratio, but polystyrene‐rich shells are found in all cases, with increasing thickness as the chloroprene/styrene ratio was reduced. The styrene‐rich products (i.e., 40/60 Neoprene/XPS ratio) appear to have larger unstained domains suggesting phase separation. For the AIBN‐initiated styrene polymerization, shells are less evident, and where they exist, are both thinner and less continuously developed. Domain sizes are somewhat larger. This relatively hydrophobic initiator has caused polymerization predominately in the interior of each latex particle. The particle size distribution of the seed neoprene latex is broad and bimodal. As the LIPNs form, the larger diameter component increases and little evidence for fresh nucleation, in the form of small diameter particles, is seen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 629–638, 1999     

Interfacial‐initiated seeded emulsion polymerization: preparation of polystyrene/poly(methacrylic acid) core/shell particles in the absence of surfactant

Composite polymer particles with hydrophobic polystyrene (PSt) as the core and hydrophilic poly(methacrylic acid) (PMAA) as the shell were prepared through two‐stage emulsion polymerization without any surfactant. In the first step, narrowly distributed PSt seed particles were prepared by surfactant‐free emulsion polymerization with 2,2′‐azobis(2‐methylpropionamide) dihydrochloride (AMPA) as the initiator. In the second step, hydrophilic PMAA shells were fabricated onto PSt seed particles through redox interfacial‐initiated seeded emulsion polymerization with cumyl hydroperoxide (CHPO)/ferrous sulfate/ethylenediaminetetraacetic acid (EDTA)/sodium formaldehydesulfoxylate (SFS), where the initiation took place mainly at the interface between PSt seed particles and the aqueous medium. The composite particles were characterized with transmission electron microscopy, fourier transform infrared spectroscopy and dynamic light scattering, and the results show that a core/shell structure was successfully built. Hydrodynamic radius (R_h) of the composite particles increased with the amount of polymerized monomers in the seeded emulsion polymerization. Copyright © 2006 Society of Chemical Industry     

高稳定性双水相共聚物PAM-AMPS的合成与表征

采用双水相聚合技术,以硫酸铵水溶液为反应介质,过硫酸铵和亚硫酸氢钠氧化还原体系为引发剂,丙烯酰胺(AM)和2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为反应单体,聚2-丙烯酰胺基-2-甲基丙磺酸(PAMPS)为稳定剂,制备了稳定的阴离子聚丙烯酰胺(PAM-AMPS)双水相分散液。采用FTIR、XRD、TG及DTA对产物进行了表征,并对其分散液进行了TEM与稳定性分析。结果表明:共聚物PAM-AMPS为无定形态的非晶聚合物,且热稳定性好;PAM-AMPS双水相分散液稳定性能优良,动力学不稳定指数(TSI)≤0.4,分散相为球形或椭球形液滴,平均粒径为186.2 nm。流变测试显示:ρ(NaCl)=2×10~4mg/L时,PAM-AMPS双水相分散液质量分数(以体系总质量计,下同)从0.2%增至1%,该混合体系黏度从8.22 Pa·s增到60.74 Pa·s;NaCl质量浓度从1×10~4mg/L增至5×10~4mg/L时,含质量分数0.2%的PAM-AMPS双水相分散液的混合体系黏度从10.80 Pa·s降至5.94 Pa·s。因而PAM-AMPS双水相分散液表现出优良的稠化及耐盐性能。     

亚微米级复合材料微粒合成研究

在乙醇-水混合溶剂中,用过硫酸钾(KPS)作为引发剂,通过乳液聚合作用来合成直径为375nm的聚苯乙烯(PSt)微球,并作为种子用于种子乳液聚合.用PEGm大分子单体作为稳定剂、偶氮二异丁腈作为引发剂,采用种子乳液聚合法,聚合苯乙烯和丙烯腈,制得特殊形态的亚微米尺寸的PEGm接枝共聚复合颗粒PEGm-g-PSAN.扫描电子显微镜(SEM)显示苯乙烯和丙烯腈同时促成了特殊形态.苯乙烯和丙烯腈的浓度、总单体浓度、引发剂类型和单体加入方式显著影响复合聚合物颗粒的形态.     

Ultrasound assisted in situ emulsion polymerization for polymer nanocomposite: A review

This review covers an ultrasound assisted synthesis of polymer nanocomposites using in situ emulsion polymerization. First of all, surface modification of core nanoparticles with a coupling agent and surfactant has been employed for the synthesis of core–shell polymer nanocomposites. In addition to application of ultrasound for the synthesis of core–shell polymer nanocomposites, due to its influential efficiency, sonochemistry has been extensively used not only as an aid of dispersion for inorganic nanoparticles and organo-clay, but also acts as an initiator to enhance polymerization rate for synthesis of polymer nanocomposites. In situ emulsion polymerization of hydrophobic monomers, such as methyl methacrylate, butyl acrylate, aniline, vinyl monomers and styrene, using surfactant and water soluble initiator were carried out for a synthesis of core–shell polymer nanocomposite. This technique assists in preparation of stable and finely dispersed polymer nanocomposite with the loading of inorganic particles up to 5 wt.%. Recent developments in the preparation of core–shell polymer nanocomposites using an ultrasound assisted method with their physical characteristics such as morphology, thermal, and rheological properties and their potential engineering applications have been discussed in this review.     

汽车工业滤纸用水乳液树脂的合成及应用研究

研究了以苯乙烯(st)和丙烯酸丁酯(BA)为单体,以十二烷基苯磺酸钠(DBS)、壬基酚聚氧乙烯醚(NP-10)为乳化剂,过硫酸铵(APS)为引发剂,加入少量功能单体Ⅳ-羟甲基丙烯酰胺(NMA),用恒温水浴控制温度,经过预乳化和聚合两阶段,制备苯丙乳液.通过红外光谱(FT-IR)和透射电镜(TEM)对乳液进行表征,并研究了其在汽车工业滤纸上的使用性能,得到乳液的最佳配方和最佳聚合工艺.合成的水性树脂乳液其粒径大小及粒径分布达到最佳,应用于纸质滤材上,呈现了较好耐水性、透气性等特点.     

大粒径磁性高分子微球的合成

本文研究了苯乙烯、丙烯酸等单体在磁性氧化铁(E_((?)3)O_4)的醇/水分散体系中的聚合行为。为了改善磁性氧化铁粒子与苯乙烯单体间的亲合性,加入聚乙二醇作为分散剂和稳定剂,制备出粒径为30～1000μm的具有磁响应性的聚苯乙烯微球。研究了控制聚合区域的方法,考察了分散稳定剂、分散介质、引发剂种类和用量、反应时间等因素对聚合行为及微球形成的影响。