Miniemulsion polymerization of styrene using well-defined cationic amphiphilic comblike copolymers as the sole stabilizer

Well-defined, positively charged, amphiphilic copolymers containing long alkyl side chains were used as stabilizers in the miniemulsion polymerization of styrene. The copolymers were prepared by controlled free-radical copolymerization of styrene and vinyl benzyl chloride using either the reversible addition-fragmentation chain transfer method or TEMPO-mediated polymerization. The benzyl chloride moities were modified by two different long alkyl chain tertiary amines (N,N-dimethyldodecyl amine and N,N-dimethylhexadecyl amine) to yield the amphiphilic copolymers with vinylbenzyl dimethyl alkyl ammonium chloride units. Owing to their high structural quality, only a small amount of these copolymers was required to stabilize the latex particles (0.5–2 wt% vs styrene). Moreover, in the absence of any hydrophobic agent, the amphiphilic comblike copolymer preserved the colloidal stability of both the initial liquid miniemulsion and the final latex. Ill-defined, analogous copolymers were synthesized by conventional free-radical polymerization and in comparison, exhibited poor stabilization properties.     

有无N-异丙基丙烯酰胺制备纳米微胶囊机理的比较

通过研究交联剂对颗粒形态的影响, 提出小分子烃的逃逸是导致生成大量小尺寸实心粒子的主要原因, 而交联剂的加入在一定程度上能抑制小分子烃的逃逸. 将N-异丙基丙烯酰胺单体引入小分子烃为模板的细乳液聚合法制备的纳米微胶囊体系中, 水相引发形成的聚N-异丙基丙烯酰胺(PNIPA)齐聚物自由基在聚合温度下(大于最低临界溶液温度)析出并被细乳液液滴吸附, 在热力学推动力和静电斥力的共同作用下, PNIPA齐聚物倾向于分布在液滴和水的界面上, 使液滴界面成为主要的聚合场所, 单体从液滴内部向界面扩散补充消耗的单体, 生成的聚合物在液滴界面上析出, 包覆小分子烃液滴, 最终得到纳米微胶囊.     

氨基甲酸酯催化剂有机纳米酸的制备

Metal-free catalysts are preferred during these days in organic synthesis or in polymerizations.Sulfonic acid is reported to be efficient in catalyzing reactions between isocyanates and alcohols.In this work,synthesis of sulfonic acid immobilized organic nanoparticles (nanoacid) and its application in catalyzing urethane formation,are elaborated.The nanoacid can be simply prepared by miniemulsion polymerization with a reactive surfactant,namely sodium 4-((perfluoronon-8-en-1-yl) oxy) benzenesulfonate,followed by an acidification.From the images of scanning electron microscope,the nanoacid obtained is found to be narrowly dispersed and the average diameter is around 90 nm.The measured sulfur content is 0.5%,from which the content of sulfonic acid in the nanoparticles is calculated to be 0.16 mmol/g.When catalyzing urethane formation based on hexamethylene diisocyanate and n-butanol,the nanoacid catalyst exhibits considerable efficiency.     

氟代丙烯酸酯三元共聚物细乳液的合成与表征

在低乳化剂用量和不加助乳化剂的条件下,采用细乳液聚合方法,合成了平均粒径在110～150nm的氟代丙烯酸酯(FA)、甲基丙烯酸甲酯(MMA)及甲基丙烯酸丁酯(BMA)三元共聚物乳液.利用GPC,FTIR及¹HNMR谱表征了共聚物分子量和结构组成,采用激光光散射法研究了聚合过程中粒径变化规律,通过接触角方法对共聚物表面性能进行了表征.结果表明,油溶性引发剂AIBN引发FA-MMA-BMA三元细乳液共聚合的主要成核场所为单体液滴.即每个单体液滴都是一个独立的微型反应器,可避免因为单体水溶性的差异而使共聚组成产生漂移.细乳液聚合合成含氟共聚物乳液的分子量分布窄(1.3～1.5),乳液稳定性能好,共聚物在低含氟量下即表现出优异的疏水疏油性能.     

Miniemulsion polymerization of cyclodextrin nanospheres for water purification from organic pollutants

The pollution of groundwater and wells has become an environmental and economic hazard as a result of waste spillage, and industrial applications such as pesticides in agriculture. Conventional treatment techniques such as sand filtration, sedimentation, flocculation, coagulation, chlorination, and activated carbon are not very effective in reducing the concentration of the organic pollutants in the presence of dissolved organic matter. The objective of the current work is to design an efficient technology for water purification from organic contaminants by a new class of polymeric nanospheres based on cyclodextrins as building blocks. We synthesized a series of cross-linked cyclodextrin polymeric nanospheres of different sizes by a unique method, miniemulsion polymerization. These cyclodextrin nanospheres exhibit a high ability to absorb aromatic organic molecules such as toluene and phenol. Sorption experiments in solutions with high concentrations of corresponding organic molecules show a high adsorption capacity.     

Nanocomposite particles with core-shell morphology IV: an efficient approach to the encapsulation of Cloisite 30B by poly (styrene-<Emphasis Type="Italic">co</Emphasis>-butyl acrylate) and preparation of its nanocomposite latex via miniemulsion polymerization

In this work, miniemulsion polymerization was applied for encapsulation of Cloisite 30B, an organically modified montmorillonite, inside poly (styrene-co-butyl acrylate) nanocomposite through an efficient and optimized procedure. The primary miniemulsions were prepared by dispersing Cloisite 30B in the monomers mixture (styrene and butyl acrylate) in the presence of sodium dodecyl sulfate and Span 80 as surfactants and hexadecane as costabilizer by using ultrasonication. The stability of both miniemulsion and the obtained latex depends on premixing procedures, time and pulsed cycle of ultrasonication, and more importantly on the applied surfactants. The synthesized products were characterized by dynamic light scattering, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, induced coupled plasma, and Zeta potential measurement. Its prepared film shows an excellent transparency, which is indicative of full exfoliation of Cloisite 30B platelets by poly (styrene-co-butyl acrylate) latex particles through miniemulsion polymerization technique with 73% efficiency. No armored latex particle was observed.     

水溶性和油溶性引发剂引发γ-甲基丙烯酰氧基丙基三甲氧基硅烷/苯乙烯细乳液共聚合的比较

分别用水溶性的过硫酸钾(KPS)和油溶性的2,2′-偶氮二异丁腈(AIBN)为引发剂引发γ-甲基丙烯酰氧基丙基三甲氧基硅烷(MPS)/苯乙烯(St)细乳液共聚合反应.比较了两类引发剂对MPS/St共聚合动力学(包括硅氧烷水解动力学和MPS/St的自由基共聚合动力学)、乳胶粒稳定性和共聚产物微结构的影响.     

高Fe_3O_4含量单分散P(St/AA)复合微球的合成与表征

在表面由十一烯酸和油酸共同修饰的Fe3O4磁流体存在下,以苯乙烯(St)和丙烯酸(AA)为共聚单体,用细乳液聚合法,制备了单分散,高Fe3O4含量,且表面带有羧基的超顺磁性高分子复合微球.采用透射电镜(TEM),热重分析(TGA),物性测量系统(PPMS),Zeta电位以及红外光谱等手段对磁性复合微球的各项性能进行表征.结果表明,Fe3O4粒子的表面改性是影响复合微球Fe3O4含量及形貌的关键因素.在优化的实验条件下,可以制得Fe3O4含量高达77wt%,平均粒径为137·9nm,表面羧基密度0·0894mmol/g,比饱和磁化强度为44·7emu/g的单分散超顺磁性高分子复合微球.     

微滴乳液聚合及其应用

微滴乳液聚合的显著特征是珠滴成核的比例增加甚至占主导地位。珠滴成核几乎不需要水相传质过程,因此,可制备多种通过其它聚合方式无法轻易得到的材料,如超顺磁性乳胶粒、高固含量低粘度乳液、胶囊化无机粒子等。本文主要阐述微滴乳液聚合的基本原理、方法以及单体微滴乳液的制备和聚合,并介绍了微滴乳液聚合的应用。