苯乙烯-甲基丙烯酸甲酯悬浮-乳液复合聚合过程中聚合物复合粒子组成的变化

采用苯乙烯(St)悬浮聚合过程中滴加甲基丙烯酸甲酯(MMA)乳液聚合组分,悬浮乳液复合聚合(SECP)方法,制备大粒径聚苯乙烯聚甲基丙烯酸甲酯(PS- PMMA)复合粒子.采用FTIR、1H- NMR、13C- NMR分析方法,研究SECP各个时期复合粒子中MMA- St链节摩尔比,发现悬浮粒子中MMA St链节摩尔比逐渐增大,而PMMA乳胶粒子中逐渐减少,表明悬浮相和乳液相间存在物质传递过程.悬浮粒子中MMA链节质量与MMA总投料质量比主要由乳胶粒子生成速率和乳胶粒子向悬浮粒子凝聚速率决定.最终得到的复合粒子除含PS和PMMA均聚物外,还含少量MMA-St共聚物.     

聚甲基丙烯酸甲酯/聚甲基丙烯酸-2-羟乙酯复合微球的合成及药物吸放性能

采用在甲基丙烯酸甲酯（MMA）悬浮聚合过程中滴加甲基丙烯酸-2-羟乙酯（HEMA）乳液聚合组分的悬浮-乳液耦合聚合方法,制备了大粒径聚甲基丙烯酸甲酯／聚甲基丙烯酸-2-羟乙酯（PMMA／PHEMA）复合微球。PMMA／PHEMA复合微球表面以HEMA乳液聚合物为主,且具有微孔结构。PMMA／PHEMA复合微球在水和苄醇中的平衡溶胀率大于PMMA微球。PMMA／PHEMA复合微球48h异丁苯丙酸负载百分比为35．6％,PMMA为27．6％。在磷酸盐缓冲液中释放时间达到360h,释放量占负载总量的82％;而PMMA微球的释放时间为216h,释放量仅占负载总量的60％。     

新型乳液聚合制备疏松PMMA树脂及成粒机理

采用以水相为分散相、甲基丙烯酸甲酯 (MMA) 环己烷混合物为连续相的新型乳液聚合制备PMMA树脂 .发现 ,在未加乳化剂和加入少量Tween2 0乳化剂时 ,均可制备由初级粒子凝聚而成、无明显皮膜结构的疏松PMMA粒子 ,初级粒子粒径小于环己烷存在下MMA悬浮聚合得到的PMMA粒子的初级粒子 .根据聚合体系相构成、PMMA在MMA 环己烷混合液的溶解性及PMMA粒子粒径分布和形态的演变 ,提出了在分散水滴内乳液聚合形成初级粒子 生长 凝聚的新型乳液聚合成粒机理     

复合微乳液聚合制备P(MMA-UA)纳米乳胶粒子的研究

将聚氨酯预聚体可聚合乳化剂 (APUA)和甲基丙烯酸甲酯 (MMA)的复合微乳液体系 ,分别用水溶性过硫酸钾 (K2 S2 O8)和油溶性偶氮二异丁腈 (AIBN)作引发剂 ,进行微乳液聚合研究 ,制备了P(MMA UA)复合纳米乳胶粒子 .研究了APUA用量、聚合温度对聚合动力学的影响 ;用透射电子显微镜 (TEM)观察了不同乳化剂浓度及引发剂体系对胶粒形态、大小及分布的影响 .结果表明 ,用可聚合乳化剂APUA可制得稳定性很好的P(MMA UA)纳米级核 壳型乳胶粒子 ,乳胶粒径在 5 0nm左右 .随着乳化剂用量增加 ,粒子变小 ;不同类型的引发剂对胶乳的性质有较大影响 ,以APUA为乳化剂 ,K2 S2 O8为引发剂 ,在聚合反应过程中或在聚合反应后的放置中 ,会出现P(MMA UA)的纳米水凝胶 (Nanogel)现象 .     

P（MMA—co—AA）乳液的制备及pH响应特性

以过硫酸钾(KPS)为引发剂、十二烷基硫酸钠(SDS)为乳化剂,利用正相乳液聚合制备(甲基丙烯酸甲酯-co-丙烯酸)共聚物(P(MMA-co-AA))乳液.通过测定聚合转化率和观察聚合过程稳定性,探讨了AA与MMA不同质量比时制备稳定的共聚物乳液的工艺条件;通过黏度法测定了乳液在不同pH时的相对黏度η,利用粒度分析仪分析了乳胶粒子在不同pH时的平均粒径和粒径分布.结果表明:AA含量较高时,控制聚合时间是得到稳定聚合物乳液的关键,当m(AA)/m(MMA)=12.5/100,65 ℃下反应120 min时,所制得的乳液稳定性最好.随着pH增大,乳液黏度先增大后降低;随着m(AA)/m(MMA)增加,制得的乳液pH敏感性增大;随着乳液从酸性(pH=5.17)变到碱性(pH=8.61),聚合物乳胶粒子平均粒径减小,粒径分布变窄.     

苯乙烯与甲基丙烯酸甲酯在聚乙二醇水溶液中无皂乳液共聚的粒径变化

利用高倍光学显微镜、库尔特粒径测试仪、TEM及zeta电位跟踪观测了苯乙烯(St)与甲基丙烯酸甲酯(MMA)在聚乙二醇(PEG)水溶液无皂乳液共聚过程中的粒径、粒径分布以及zeta电位变化.聚合物粒径会经历由小到大(某些粒径甚至超过1000μm,分布在0.04～2000μm的极宽范围内),再由大变小(形成的数均分布在0.04～0.18μm)过程,且粒径分布也由宽变窄,最终粒径数均分布集中在0.04～0.18μm窄范围内.结合聚合转化率数据,根据PEG水溶液中进行的St/MMA无皂乳液共聚粒径变化过程,以及zeta电位在聚合过程中异于普通无皂乳液的现象,认为该体系在反应初期形成的粒子会形成粒子堆,并随着聚合反应的继续,带有离子片段的自由基链段不断扩散进入粒子堆表面的小粒子,使其zeta电位不断增强,最终脱离粒子堆.提出了PEG水溶液中St/MMA无皂乳液共聚聚并脱析成核机理.     

PU-St超浓乳液聚合动力学及聚合物性质的研究

采用一步法制备聚氨酯预聚体 ( PU)苯乙烯 ( St)超浓乳液 ,探讨了稳定的超浓乳液的 NCO/OH和 St/PU最佳比例范围。研究了乳化剂和引发剂浓度对超浓乳液聚合的稳定性及聚合动力学的影响 ,并制得了用 PU改性的聚苯乙烯 ( PS)粉状树脂。测定了乳胶粒子大小、粒径分布、分子量和聚合物膜的动态力学性质。发现乳胶粒子大小及其单分散性随聚合转化率的增加而增加 ;与本体聚合比较 ,聚合物的分子量有明显增大 ;PU- PS复合聚合物具有优良性能。     

反应性复合乳液的合成、表征及其交联反应

利用种子半连续乳液聚合方法合成了核层或壳层带有环氧基以及壳层带有羧基的3种不同核/壳结构的乳胶粒子,通过物理共混带环氧基和羧基的乳胶粒子,得到了两种反应性复合乳液.利用透射电镜和激光动态光散射对乳胶粒子进行了表征,其粒径分布较窄,粒径分布的多分散系数为0.062,平均粒径约76 nm,乳胶粒子具有明显的核/壳结构.通过胶膜的凝胶率和膨胀率的测定和红外光谱分析对反应性复合乳液中乳胶粒子的扩散及交联反应进行了研究,并探讨了不同核壳结构复合乳液对涂膜机械性能的影响.研究表明,当反应性复合乳液中的环氧基和羧基分别分布在乳胶粒子的核层和壳层时,有利于聚合物分子链的充分扩散和化学交联反应的进行,从而提高涂膜的物理化学性能,当甲基丙烯酸缩水甘油酯(GMA)含量为10 wt%时,涂膜的拉伸强度达20.3 MPa.     

可聚合乳化剂制备纳米色料的形貌及其影响因素

以α-烯烃磺酸钠(AOS)为可聚合乳化剂、苯乙烯(St)为非极性单体、甲基丙烯酸甲酯(MMA)为极性单体、二乙烯基苯(DVB)为交联剂、十六烷(HD)为助稳定剂,通过细乳液聚合法制备了聚合物包覆蒽醌类染料的纳米色料。利用透射电子显微镜(TEM)、激光粒度仪(DLS)等研究了可聚合乳化剂、极性单体和交联剂的用量对纳米色料形貌的影响。结果表明:该纳米色料具有明显的核壳结构,且乳液的稳定性好。随着乳化剂用量的增加,粒子粒径变小;少量极性单体的加入有助于得到粒径分布较窄的核壳结构纳米粒子,交联剂和单体彼此极性的差异会导致粒子表面粗糙。以St为聚合单体,当DVB的质量小于St质量的30%时,能够得到结构规整的纳米粒子,超过30%时,纳米粒子表面不再光滑。而以MMA为聚合单体,当DVB的质量为MMA的8%~30%时,粒子表面均凹凸不平。     

超声辐照引发MMA微乳液聚合

研究了超声波引发甲基丙烯酸甲酯(MMA)的微乳液聚合.辐照40min时单体转化率高达90%.透射电镜观察发现,PMMA微乳液平均粒径为36.5nm,粒径分布窄,表明超声波引发是制备PMMA微乳液的有效方法.采用分光光度计对微乳液聚合过程中乳胶粒的形成和大小进行了间接表征,研究了超声功率输出、乳化剂、助乳化剂、单体和引发剂对MMA微乳液聚合的影响.     

聚硅氧烷/丙烯酸酯核/壳复合胶乳的粒径分布与成核机理

通过种子乳液法合成出具有高有机硅含量核 壳结构的聚硅氧烷 丙烯酸酯复合粒子 .研究了聚合方法、乳化剂浓度、引发剂浓度、单体滴加速度等工艺条件对复合乳液粒径尺寸、分布与形态的影响 ,并对复合乳液的成核机理进行了探讨 .研究表明 ,乳化剂浓度对乳液粒子的粒径分布和形态、结构有显著影响 ,引发剂浓度增加将使粒子粒径减小 ;相对一次投料法 ,种子乳液法生成的粒子分布窄 ,具有明显核壳结构 ,通过壳层单体滴加速度可以控制粒子的粒径尺寸和分布 ;而壳层丙烯酸酯聚合物主要是在聚硅氧烷种子表面的“过渡层”聚合、富集而成 .     

The suspension�Cemulsion combined polymerization of fluorinated acrylic monomer and the fluorinated latex film surface properties

The perfluoroacrylate-containing copolymer composite particles were fabricated by suspension?Cemulsion combined polymerization (SECP). The features and formation mechanism of resulting polymer particles in SECP were studied. The fluorinated latexes with better stability and those fluorinated films with high surface fluorine content were prepared by SECP using fluorine-free surfactants as an emulsifying agent, and the surface natures of the fluorinated films were characterized. It was found that P(MMA?CBA) latex particles gradually coagulated with P(PFA?CBA) particles after adding emulsion polymerization constituents at the midstage of the suspension polymerization, and fluorinated composite particles with core?Cshell structure and larger size were obtained. The fluorine contents either on the film surface or in the bulk of the film and the films from SECP are higher than those from miniemulsion polymerization at high PFA feed ratio (more than 20?wt.%). The model of PFA?CMMA?CBA SECP was proposed according to the variations of particle features of the composite particles.     

The characterization of latex particles prepared by pulsed electron beam induced emulsion polymerization

The emulsion polymerization of styrene (St) and methyl methacrylate (MMA) induced by 10 MeV pulsed electron beams (PEB) was investigated. The monomer conversion of MMA and St was found to be very low so that the final prepared poly(methyl methacrylate) (P(MMA)) and polystyrene (PS) latex particles exhibit porous structures, as verified by TEM and SEM observations. The results of dynamic light scattering (DLS) and gel permeation chromatography (GPC) showed that both the particle size and the molecular weight of PS and PMMA latexes decrease with the increase of the absorbed dose. However, the molecular weights and the particle sizes of the PS and PMMA latexes change differently with the irradiation time. This work indicated that emulsion polymerization induced by high energy electron beam has an advantage over that induced by γ-ray or chemical initiators in the preparation of latex with a low molecular weight and porous structure.     

Polar Gradient Latex Particles with Hydrophilic Core and Hydrophobic Shell Prepared via Multistep Emulsion Polymerization

Monodisperse polar gradient particles were synthesized via a three‐step emulsion polymerization using poly(butyl acrylate‐methyl methacrylate‐methacrylic acid‐ethylene glycol dimethacrylate) (P(BA‐MMA‐MAA‐EGDMA)) as core, poly(methyl methacrylate‐methacrylic acid‐styrene) (P(St‐MMA‐MAA)) as interlayer and polystyrene (PSt) as shell. The particle growth and encapsulation in each emulsion polymerization step were followed by transmission electron microscopy (TEM), dynamic light scattering (DLS) and conductometric titration. Results indicated that the feeding mode and the interlayer were essential to prepare the polar gradient latex particles with hydrophilic core and hydrophobic shell. The morphologies of the two‐layer core/interlayer and three‐layer core/interlayer/shell particles were observed in TEM micrographs, and the sequential encapsulations of the carboxyl‐containing core and the core/interlayer particles were confirmed by an increase in the particle size as well as an increase in the buried carboxyl percentage.     

Effects of surfactants on the morphology of composite polymer particles produced by two‐stage seeded emulsion polymerization

Poly(methyl methacrylate) (PMMA)–polystyrene (PS) composite polymer particles were synthesized in the presence of a surfactant by two‐stage seeded emulsion polymerization. The first stage was the synthesis of PMMA particles by soapless emulsion polymerization; the second stage was the synthesis of the PMMA–PS composite polymer particles with the PMMA particles as seeds. In the second stage of the reaction, three kinds of surfactants—sodium laurate sulfate (SLS), polyoxyethylene (POE) sorbitan monolaurate (Tween 20), and sorbitan monolaurate (Span 20)—were used to synthesize the PMMA–PS composite particles. Both the properties and concentrations of the surfactants influenced the morphology of the composite particles significantly. Core–shell composite particles, with PS as the shell and PMMA as the core, were synthesized in the presence of a low concentration of the hydrophilic surfactant SLS. This result was the same as that in the absence of the surfactant. However, a low concentration of Tween 20 led to composite particles with a core/strawberry‐like shell morphology; the core region was a PS phase, and the strawberry‐like shell was a PS phase dispersed in a PMMA phase. With an increase in the concentration of SLS, the morphology of the composite particles changed from core (PMMA)–shell (PS) to core (PS)–shell (PMMA). Moreover, the effects of a high concentration of Tween 20 or Span 20 on the morphology of the PMMA–PS composite particles were investigated in this study. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2224–2236, 2005     

Synthesis of submicron-sized peanut-shaped poly(methyl methacrylate)/polystyrene particles by seeded soap-free emulsion polymerization

Submicron-sized peanut-shaped poly(methyl methacrylate)/polystyrene(PMMA/PS) particles were successfully synthesized by seeded soap-free emulsion polymerization of styrene on the spherical crosslinked PMMA seed particles.The obtained peanut-shaped particles showed a novel internal morphology:PS phase formed one domain which linked to the other domain having PMMA core encased by PS shell.     

Polyaniline microsphere encapsulated by poly(methyl methacrylate) and investigation of its electrorheological properties

Microspheres consisting of a poly(methyl methacrylate) (PMMA) shell wrapping the conductive polyaniline (PANI) particle as a core were prepared by an in-situ suspension polymerization method and then adopted as an electrorheological (ER) material. The polymerization reaction and encapsulation were confirmed by Fourier transform infrared spectrum analysis. The rod-like PANI particles were synthesized via an emulsion polymerization protocol and observed by transmission electron microscopy. In addition, a spherical shape of encapsulated PANI/PMMA (core/shell) microspheres was observed by scanning electron microscopy. The thermal stability of PANI/PMMA particles was examined by use of thermogravimetric analysis. The PANI/PMMA particle-based suspension in silicone oil exhibited typical ER behavior. The conductivity of PANI/PMMA particles was much lower than that of the rod-like PANI.