有机硅氧烷改性St/BA/AA三元共聚乳液的制备

采用核壳乳液聚合法,制备了乙烯基三乙氧基硅烷（VTES）改性的St/BA/AA三元共聚乳液,其结构经FT IR确证。研究了VTES用量、乳化剂用量及配比和引发剂用量对单体转化率和粒径的影响。结果表明：在最优条件［48%St, 48%BA, 4%AA, 1%N-MA, 4%VTES, 8%乳化剂（OP-10/SDS=1/3）, 0.8%引发剂］下,单体转化率为95.8%,平均粒径242 nm。并研究了改性St/BA/AA乳胶膜(1)的耐溶剂性和铅笔硬度。结果表明：1具有良好的耐溶剂性,铅笔硬度为2H。     

室温交联型硅丙微胶乳的合成研究(1)硅烷单体对聚合稳定性和胶膜性能的影响

采用种子微乳液聚合工艺和单体半连续滴加法合成了室温交联型有机硅改性丙烯酸酯微胶乳，研究了硅烷单体种类和用量及其添加顺序等对聚合稳定和胶膜性能的影响。结果表明，使用含阻碍性铁新硅烷单体（C－1757）可明显抑制体系中的水解－缩合反应，提高聚合稳定性，而且随其用量增加，改性胶膜的交联密度增大，拉伸强度提高；延迟添加C－1757，可进一步提高聚合稳定性，但会降低胶膜的交联密度，拉伸强度先高后低，30／70处有一个最大值，所合成的硅丙微胶乳储存期可达长两年，与C－1757相比，硅烷单体A－174改性的胶膜具有更大的交联密度，而A－171改性的胶膜交联密度偏低，力学性能较差。     

乙烯基硅烷-丙烯酸酯乳液共聚动力学研究

以乙烯基三乙氧基硅烷(VTES)、丙烯酸酯为单体,乙氧基醇磺基琥珀酸二钠(A—102)为乳化剂,合成了有机硅改性丙烯酸酯共聚乳液。研究了乳化剂、引发剂、VTES、反应温度以及功能性单体甲基丙烯酸羟乙酯(HEMA)对乳液共聚反应速率的影响。结果表明:聚合速率随乳化剂浓度、引发剂浓度、HEMA浓度的增大及反应温度的升高而增大,但随VTES浓度增大而逐渐减小。由实验得出恒速阶段聚合反应速率R_p与乳化剂浓度C_E、引发剂浓度C_1及有机硅单体浓度C_(VTES)的关系为R_p∝C_E~(0.35)C_I~(0.48)C_(VTES)~(-0.64),表观活化能E_a为81.1kJ·mol~(-1)。     

有机硅改性聚氨酯丙烯酸酯细乳液的制备及性能

将自制的聚氨酯大单体与含乙烯基有机硅单体、丙烯酸酯进行共聚反应,通过合适的工艺条件,制备了一系列性能稳定的细乳液。研究了聚合方法、有机硅含量对共聚细乳液及胶膜性能的影响。结果表明,种子细乳液法制得的聚合物结构明确,细乳液粒径均在150 nm左右,分布指数约为0.07,有机硅的引入使乳液胶膜耐水性及耐高温性得到了明显提高。     

pH值对硅油乳液Zeta电位及其制备的影响

1994年,T．M．Obey和V．Brian采用二甲基二乙氧基硅烷在氨水催化剂下进行乳液聚合,获得了具有较好单分散性的聚二甲硅油乳液。本文研究了pH值对二甲基二乙氧基硅乳液Zeta电位的影响,比较了有相同单体浓度的单相体系在低pH值(酸性)和高pH值(碱性)条件下乳液聚合的规律,以期对硅烷乳液制备做更进一步的研究。     

聚苯基硅氧烷/聚丙烯酸酯复合乳液的合成与性能

本文以二苯基二甲氧基硅烷(DPDMS)和γ-甲基丙烯酰氧基丙基三甲氧基硅烷(MAPTMS)合成了具有微交联结构的聚硅氧烷乳液,并以此为种子乳液再与丙烯酸酯类单体聚合,合成了稳定且性能优良的聚硅氧烷/聚丙烯酸酯复合乳液.用激光粒度分析仪、FTIR、DMA等进行了表征.结果表明,硅氧烷被有效的接枝到了聚丙烯酸酯分子链中;硅氧烷的加入,使聚合物的储能模量,损耗模量增大,玻璃化温度提高,加入量为10％时,Tg由50.5℃升高到57.2℃;加入20％的硅氧烷涂膜吸水率由13.8％降低到6.8％.     

有机硅改性丙烯酸酯共聚乳液合成方法及胶膜性能的研究

用一次投料法、单体乳液滴加法和引发剂滴加法有机硅改性丙烯酸酯共聚乳液，聚合过程、胶粒形态及乳液稳定性的观测结果表明：单体乳液滴加法是合成该类乳液的最佳方法，研究了单体乳液滴加法中有机硅含量与聚合反及胶膜性能的关系，结果表明：有机硅含量在１５％以下时，聚合反应可以顺利进行，胶膜性能不仅依赖于聚合时有机硅单体的总量，而且还依赖于有机硅单体中活性硅氧烷所占的比例。     

乙炔和三乙氧基硅烷的硅氢加成反应研究

制备了氯铂酸-异丙醇、氯铂酸-聚甲基乙烯基硅氧烷和氯铂酸-三苯基膦三种催化剂,评价了它们在乙炔与三乙氧基硅烷的硅氢加成反应中的催化活性及选择性;并考察了反应温度、乙炔流量、氯铂酸-聚甲基乙烯基硅氧烷与三乙氧基硅烷摩尔比、PPh3/H2PtCl6摩尔比等因素对产物收率的影响.结果表明,氯铂酸-聚甲基乙烯基硅氧烷对该反应表现出较高的催化活性,在催化剂与三乙氧基硅烷摩尔比为1.2×10-4∶1,T=80℃,乙炔流量=120 mL/min的条件下反应,产物乙烯基三乙氧基硅烷的选择性为100%,收率可达97.5%.     

聚甲氧基硅氧烷及其功能化产物研究Ⅰ.制备

通过正硅酸甲酯(TMOS)在酸性条件下的部分水解缩合反应制备了不同分子量的聚甲氧基硅氧烷(PMOS)，详细讨论了水与TMOS的摩尔比(r)对PMOS结构和性能的影响。用丙烯酸-2-羟乙酯(HEA)通过酯交换反应使PMOS的部分甲氧基变为丙烯酰氧乙氧基，从而得到可进行热聚合或光聚合反应的功能化聚甲氧基硅氧烷PAMOS，讨论了影响酯交换反应的各种因素。     

甲基丙烯酸3-三甲氧基硅丙酯/苯乙烯细乳液共聚合过程中的水解及缩合反应

研究了甲基丙烯酸3-三甲氧基硅丙酯(MPS)和苯乙烯(St)细乳液聚合过程中的水解及缩合反应.用气相色谱仪测定聚合过程中水解产物——甲醇的含量来研究MPS的水解度.MPS分子主要在细乳液液滴与水的界面以及乳胶粒与水的界面上发生水解反应.MPS和St比例、介质pH值、乳化剂用量、引发剂类型和用量都会影响MPS的水解程度.缩合产物用29Si固态核磁共振表征,中性条件下,缩合反应受到抑制,在高MPS/St比例的体系中也只生成少量缩合产物.酸性和碱性条件下,缩合产物量均增加,但碱性条件下,体系中仍有一定数量未缩合的硅氧烷存在,这与细乳液聚合独特的液滴成核机理及聚合过程中较少液滴间物质交换有关.     

Preparation of polyacrylate–polysiloxane core–shell latex particles

Crosslinked polymer seed latexes of butyl acrylate, methyl methacrylate and methacrylic acid were synthesized with ethylene glycol dimethacrylate as a crosslinking agent in a first step. Three different processes of seeded emulsion polymerization were used to prepare an outlayer of polysiloxane on the above seed latex particles: (A) direct anionic polymerization of D₄ (octamethyl tetracyclosiloxane) catalyzed by potassium hydroxide; (B) direct cationic polymerization of D₄ onto the seed catalyzed by dodecylbenzene sulfonic acid; (C) a vinyl-containing polysiloxane prepared by copolymerization of D₄ and vinyl septamethyl tetracyclosiloxane was added before the D₄ cationic polymerization. Characterization by transmission electron microscopy showed that only process C provided satisfactory results. Film hardness was measured, and the latex film from process C demonstrated the lowest hardness of all the films. The mechanism of polymerization is discussed.     

Emulsion Copolymerization of Vinyl Acetate and Vinyl Silanes: Kinetics and Development of Microstructure

The batch emulsion copolymerization of vinyl acetate with different vinyl silane functional monomers (vinyl trimethoxysilane [VTMS], vinyl triethoxysilane [VTES], and vinyl silanetriol [VSTO]) is studied. The nature of the silane strongly affects the development of the microstructure and crosslinking ability of the latexes. A combination of techniques (Soxhlet extraction, centrifugation, assymetric‐flow field flow fractionation AF4/MALS/RI) shows that the factor controlling the molar mass and crosslinking density is the degree of hydrolysis of the alkoxysilane, producing higher molar masses and degrees of crosslinking when the degree of hydrolysis is high. Thus, the copolymer containing VSTO produced a very crosslinked latex, the one with VTMS produced a latex with a low degree of crosslinking in the wet state that can yield high degrees of crosslinking upon drying, and the latex with VTES do not produce significant amounts of crosslinking neither before nor after drying.     

Properties of polystyrene/poly(butyl acrylate) core/shell polymers modified with N‐methylol acrylamide

Polystyrene/poly(butyl acrylate) PS/PBA polymer dispersions with core/shell particles functionalized by N‐methylol acrylamide (N‐MA) were prepared through two‐step emulsion polymerization. The influence of N‐MA situated in shell and/or in core/shell of particles on the crosslinking reaction was studied to relate its mechanical properties and organic solvent resistance of films cast from basic and modified PS/PBA latexes. The changes in the phase arrangement of functionalized and unfunctionalized films after treatment with solvent and annealing were monitored. It was found that at the presence of N‐MA the crosslinking reaction occured already during the polymerization. Films from functionalized dispersions exhibit improved tensile strength and higher resistance against organic solvent.     

Emulsion Copolymerization of Vegetable Oil Macromonomers Possessing both Acrylic and Allylic Functionalities

Summary: A soybean oil-based vegetable oil macromonomer (VOMM) was incorporated as a comonomer into an all-acrylic copolymer via semi-continuous emulsion polymerization. Structurally, VOMMs are comprised of long hydrocarbon fatty acid moieties with allylic double bonds which enable auto-oxidative crosslinking at ambient temperature. VOMMs facilitate low temperature film formation and the fatty acid chains tethered to the polymer backbone auto-oxidize upon film formation to yield crosslinked films. Latexes with varying VOMM levels were synthesized to elucidate the effect of VOMMs on the pre-cure and post-cure glass transition temperature (T_g) and minimum film formation temperature (MFT). Thermoplastic control latexes (without VOMM) were also synthesized via copolymerization of butyl acrylate and methyl methacrylate. This paper details the characterization performed to validate and quantify the VOMM allylic unsaturation retention before, during, and after polymerization, and to quantify and confirm the increase in T_g resulting from auto-oxidative crosslinking via solid state ¹³C nuclear magnetic resonance spectroscopy and differential scanning calorimetry.     

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 synthesis,interfacial, and colloidal properties of waterborne cationic methacrylic co-polymers

Two cationic polymers with similar composition were prepared by two different polymerization methods. By monitoring the evolution of the molar mass and chemical composition during the reactions together with charge density measurements and calculations, it was concluded that the cationic polymer synthesized by emulsion polymerization had a less uniform compositional distribution than the cationic polymer prepared by solution polymerization. Contributing to the heterogeneity was the hydrolysis of one monomer (dimethylamino ethylmethacrylate (DMAEMA)) during the synthesis. As a result, the polymer prepared by emulsion polymerization had a more blocky structure and was more surface active as supported by static and dynamic surface tensions data. Fluorescence experiments showed that both polymers formed aggregates at very low concentrations of approximately 0.01 wt%. The aggregates of the polymer prepared by emulsion polymerization were compact, whereas the solution polymerization-based polymer aggregates exhibited a rather expanded geometry.     

交联剂含量对憎水改性缔合型增稠剂性能的影响

以甲基丙烯酸、丙烯酸乙酯和功能单体二十二烷基聚氧乙烯醚甲基丙烯酸酯为原料,过硫酸铵为引发剂,变化交联剂邻苯二甲酸二烯丙酯(DAP)的量,采用半连续乳液聚合方法合成了DAP含量不同的憎水改性缔合型增稠剂乳液.测定了乳液的黏度和乳胶粒粒径及其分布等性能.考察了乳液运动黏度和透光率随pH的变化.随着pH值的增加,乳液的透光率...     

The control of structure in emulsion polymerization

Free-radical addition polymerization can be carried out using four different processes: mass or bulk, solution, suspension, and emulsion polymerization. Of these four processes, emulsion polymerization is unique because it is a heterogeneous process, in which the polymerization reactions can take place in three different sites: in the continuous aqueous phase, on the surface of growing particles, and within the growing particles. This unique feature of emulsion polymerization offers many possibilities for designing different polymers and latexes: e.g., high-molecular-weight polymers, uniform copolymers, copolymers of difficult-to-copolymerize monomers, functionalized (surface-modified) latexes, uniform size latex particles, grafted latexes, and structured latexes having core-shell, microdomain structures, interpenetrating polymer networks, etc. This paper will describe several aspects of the control of structure in emulsion polymerization.     

Thin-Film Morphologies of Random Copolymers as Functions of Thermal History

Series polymers of butyl methacrylate with various contents of 3-(trimethoxysilyl)propyl methacrylate (MSMA) that introduces crosslinking networks among the macromolecules upon hydrolysis and self-condensation have been synthesized by free radical polymerization, and the influence of crosslinking density on the film properties has been examined. The polymer solutions were spin-cast over a layer of polystyrene brush to yield homogeneous polymer films. When the films of about 30 nm thick were exposed to moisture and then heated at 60 degrees C for hydrolysis and self-condensation of MSMA groups, the initially flat surfaces became slightly coarser but without apparent dewetting. Further annealing at 140 degrees C resulted in dewetting of the thin films, whose morphologies in thermodynamic equilibrium were related to the chemical compositions of the polymers. The polymers having higher contents of MSMA exhibited significantly reduced dewetting at the high temperature, due to the higher density of crosslinking networks that restricted the molecular mobility. In contrast to the thin films of about 30 nm thick, thicker films (about 100 nm) showed only a slight dewetting, even non-dewetting at the elevated temperature. Copyright 2001 Academic Press.     

Alkoxysilane Functional Acrylic Latexes: Influence of Copolymer Composition on Self-Curing Behavior and Film Properties

Reactive latexes based on acrylic polymers with trimethoxysilyl groups in the side chain were prepared by semi-continuous emulsion copolymerization. The properties of the latex film related to the polymer network structure and their evolution upon thermal curing were studied as a function of the content of the reactive comonomer, trimethoxysilylpropyl methacrylate (TSPMA), ranging between 8 and 25 wt-%. In particular, the sensitivity to both organic solvent (chloroform) and water and the thermomechanical properties were investigated by swelling experiments and dynamic-mechanical analysis (DMA). The results are interpreted in terms of a transition from uniform to microheterogeneous crosslinking regime, possibly as the result of formation of polyorganosilsesquioxane-like (POSS) crosslinking domains at higher TSPMA content.