有机-无机杂化核壳型乳胶粒的制备及其粒径控制

以苯乙烯乳液聚合合成种子,再在种子外生成苯乙烯与甲基丙烯酸-3-三甲氧基硅丙酯（MPS）的共聚物,利用MPS中硅氧烷基的水解-缩合反应,形成交联的壳,得到有机-无机杂化型核壳乳胶粒.然后用溶剂将聚苯乙烯模板溶解,可得到空心微胶囊.通过透射电镜（TEM）和动态光散射粒径仪（DLS）观测乳胶粒及微胶囊的形态.并研究了乳化剂种类、介质pH值、MPS用量和加入方式对粒径、粒子数和体系稳定性的影响.发现非离子型乳化剂、酸性或碱性介质、MPS用量过多均促进乳胶粒子数减少,减弱了乳液稳定性.而采取连续滴加MPS的方法则可提高乳液的稳定性,且粒径可控.     

通过微乳液聚合法制备自交联型有机硅乳液

通过苯乙烯与甲基丙烯酸-3-三甲氧基硅丙酯(M PS)微乳液聚合,制得了稳定的自交联型水分散涂料。这种含硅涂料能在涂覆过程中发生自交联反应,不仅有效地提高了涂层的光滑度、耐候性和耐沾污性,更减少了VOC的排放量。通过透射电子显微镜和动态光散射仪(DLS)研究了聚合方法和M PS加入量对所得涂料稳定性的影响,发现微乳液聚合方法可以显著提高乳液的稳定性,而且乳液的稳定性随着M PS加入量的增加而降低。     

可自交联的硅烷改性聚苯乙烯乳液

金华市环境科学研究院的王娟等人通过乳液聚合制得聚苯乙烯种子乳液，再加入γ-甲基丙烯酰氧丙基三甲氧基硅烷，制成核壳型硅烷改性聚苯乙烯乳液。该乳液的乳胶粒结构规整、大小均匀、具有核壳结构。在γ-甲基丙烯酰氧丙基三甲氧基硅烷参与的乳液共聚反应中，需选用离子型乳化剂，反应介质的pH值保持在7左右；采用连续滴加法时，γ-甲基丙烯酰氧丙基三甲氧基硅烷的质量分数达到10％时，乳液的稳定性仍然良好。该乳液可用于配制自交联型水分散涂料。     

伴有水解缩合反应的种子乳液聚合动力学(Ⅱ) 参数求解和模型应用

通过对伴有水解缩合反应的自由基种子乳液聚合动力学模型的求解,利用甲基丙烯酸-3-三甲氧基硅丙酯（MPS）和苯乙烯通过种子乳液聚合反应,仿真了不同反应条件下的反应动力学。并通过气相色谱（GC）和29Si固态核磁共振谱（NMR）测定了不同反应条件下的水解和缩合反应的动力学,并与动力学模型的仿真结果进行了比较。发现实验结果能与模型计算结果吻合,且水解和缩合反应的速率随体系中介质pH值、乳胶粒表面积和MPS在各相中分配的不同而变化。同时还总结出模型中参数f反映了乳胶粒中水解反应特点,与乳胶粒的表面积和功能基团扩散到乳胶粒表面的难易程度有关,并得出其半经验表达式。     

中空聚合物微球的制备Ⅱ．核乳胶粒的制备

以带羧基的乳胶粒为种子进行了甲基丙烯酸甲酯、甲基丙烯酸和二乙烯基苯的种子乳液共聚合，制备了轻度交联的核乳液，将该核乳液在包壳反应并进行碱处理后，制得了中空聚合物微球。研究了核乳胶粒制备过程中羧基单体的种类、单体的加料速率、乳化剂的用量等因素对核乳胶粒直径及其分布以及中空聚合物微球结构形态的影响，结果表明，采用甲基丙烯酸作为羧基共聚单体时，比采用丙烯酸的聚合体系稳定性更好，同时也更有利于提高羧基单体的用量。实验证明，必须采用“饥饿”式单体进料方式，否则会有新乳胶粒生成且聚合稳定性变差。应采用半连续补加乳化剂工艺，当乳化剂总量为核单体总量的0．15％（wt）时能保持聚合稳定性且能保证无新乳胶粒生成。     

有机——无机复合乳液研究（Ⅱ）

3 聚合方法及动力学研究 有机—无机复合高分子乳液采用不同的乳液聚合方法,所得乳液性质也有所不同,主要的乳液聚合方法有核壳乳液聚合（种子乳液聚合）、无皂乳液聚合和类乳液聚合（emulsion-likepolymerization）。3.1 核壳乳液聚合法（种子乳液聚合）制备有机—无机复合高分子乳液 采用种子乳液聚合反应得到的聚合物乳液,在材料的复合领域内占有一定的地位,控制不同聚合条件,可以获得形态结构完全不同的乳胶粒,乳胶粒的形态结构基本可以归结为两大类型,即正常型和异常型,具体形态如图11所示。其颗粒由核和壳两部分组成,这种复合的乳胶粒结构赋予乳液许多特殊功能     

Particle stability of γ-methacryloxy propyl trimethoxysilane and styrene mini-emulsion copolymerization

研究了各聚合条件对甲基丙烯酸3-三甲氧基硅丙酯（MPS）和苯乙烯（St）细乳液共聚合体系乳胶粒稳定性的影响,聚合条件包括引发剂类型、MPS/St比例、乳化剂用量、共稳定剂用量和体系pH值。通过动态激光光散射测定初始液滴和乳胶粒的尺寸,气相色谱测定苯乙烯的转化率,总转化率由重量法测定。研究发现,油溶性引发剂偶氮二异丁腈（AIBN）引发的体系,MPS/St比例为1∶4时,聚合过程中乳胶粒尺寸基本不变,最终乳胶粒数与初始液滴数比值为0.97。相同MPS/St比例,水溶性引发剂过硫酸钾（KPS）引发的体系,随聚合反应进行乳胶粒尺寸增加,最终乳胶粒数和初始液滴数比值仅为0.55,乳胶粒发生明显聚并。随MPS/St比例增加,乳胶粒稳定性变差,乳化剂和共稳定剂量变化对乳胶粒数和初始液滴数比值影响不大。在酸性或碱性介质中,由于水解反应加剧,乳胶粒聚并严重,最终粒子数只占初始粒子数的0.25。     

甲基丙烯酸3-三甲氧基硅丙酯/苯乙烯细乳液共聚合乳胶粒稳定性

研究了各聚合条件对甲基丙烯酸3-三甲氧基硅丙酯（MPS）和苯乙烯（St）细乳液共聚合体系乳胶粒稳定性的影响,聚合条件包括引发剂类型、MPS/St比例、乳化剂用量、共稳定剂用量和体系pH值。通过动态激光光散射测定初始液滴和乳胶粒的尺寸,气相色谱测定苯乙烯的转化率,总转化率由重量法测定。研究发现,油溶性引发剂偶氮二异丁腈（AIBN）引发的体系,MPS/St比例为1∶4时,聚合过程中乳胶粒尺寸基本不变,最终乳胶粒数与初始液滴数比值为0.97。相同MPS/St比例,水溶性引发剂过硫酸钾（KPS）引发的体系,随聚合反应进行乳胶粒尺寸增加,最终乳胶粒数和初始液滴数比值仅为0.55,乳胶粒发生明显聚并。随MPS/St比例增加,乳胶粒稳定性变差,乳化剂和共稳定剂量变化对乳胶粒数和初始液滴数比值影响不大。在酸性或碱性介质中,由于水解反应加剧,乳胶粒聚并严重,最终粒子数只占初始粒子数的0.25。     

自交联型可再分散苯丙乳胶粉的制备及水分散性与耐水性的协同优化研究

软核硬壳结构苯丙乳液壳层引入自交联单体N-羟甲基丙烯酰胺(NMA),经喷雾干燥获得水分散性和涂膜耐水性俱佳的自交联型可再分散乳胶粉。采用FT-IR光谱、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、马尔文激光粒度分析、原子力显微镜(AFM)等手段对原乳液、乳胶粉、再分散乳液进行表征,研究了乳液中和、干燥和再分散过程,分析了乳胶粉能兼顾再分散性和聚合物涂膜耐水性的机理。研究结果表明,自交联型苯丙乳液具有规整的软核硬壳结构,乳胶粉的粒径在2~20μm,遇水可迅速分散得到平均粒径182 nm的再分散乳液。乳液壳层添加NMA能削弱乳胶粒表面的疏水缔合作用,形成更厚的"绒毛结构"和水化层,因而抑制干燥时的乳胶粒凝聚融合,阻止乳胶粒之间的交联反应,优化了乳胶粉的亲水分散性。自交联作用使可再分散乳胶粉所成聚合物膜的吸水性降低40%以上,因此,采用NMA交联改性同时优化了苯丙乳胶粉的水分散性与耐水性。     

MPS/OTES共聚乳液的制备与性能研究

选用γ-甲基丙烯酰氧基丙基三甲氧基硅烷（MPS）和辛基三乙氧基硅烷（OTES）为共聚单体，十二烷基硫酸钠（SDS）和聚氧乙烯辛基苯酚醚-10(OP-10)为乳化体系，采用乳液聚合方法成功制备了稳定的MPS/OTES乳液。探究了不同工艺条件对乳胶粒粒径和乳液性能的影响，利用FT-IR、SEM、TEM、纳米粒度和电位分析仪等对乳胶粒形态和结构进行了分析。结果表明：随着单体MPS质量比的增加，乳液粒径先减小后增大，MPS:OTES=2:1时，乳液的粒径最小；当酸性催化剂DBSA用量为1.33～1.67%时，乳液粒径在100 nm左右，粒径分布较窄，乳液稀释稳定性、离心稳定性、储存稳定性良好。     

通过细乳液聚合方法制备自交联型有机硅乳液

苯乙烯与甲基丙烯酸-3-三甲氧基硅丙酯(M PS)经细乳液聚合,制得了稳定的自交联型的水分散涂料,用透射电子显微镜(TEM)、动态光散射仪(DLS)和红外光谱(IR)表征了乳胶粒的形态和结构。发现与传统乳液聚合相比,细乳液聚合法可显著提高乳液的稳定性,且M PS加入量的增加会导致乳液稳定性降低。     

Controlled preparation and properties of acrylic acid epoxy-acrylate composite emulsion for self-crosslinking coatings

A stable epoxy-acrylate composite latex was successfully prepared through emulsion polymerization of modified epoxy acrylic (EPAC) oligomer with acrylate monomer. The EPAC oligomer was obtained using active acrylic acid (AA) to react with epoxy resin. And by regulating the reaction degree of the active hydrogen of AA and epoxide group, there is the acquisition of terminal double bond that gives EPAC reactivity, together with the partial retention of the epoxide group that enables self-crosslinking during film formation. The structural conformation of the oligomer was ascertained by Fourier transform infrared (FTIR) spectroscopy. The factors influencing the stability of the epoxy-acrylate composite latex were investigated. The epoxy-acrylate composite latex was the most stable when methyl acrylic acid was 1.5 wt% and modified EPAC oligomer was 15 wt% of the total monomer weight. The morphology and property of the composite latex films were characterized by scanning electron microscopy, transmission electron microscopy (TEM), and temperature-modulated differential scanning calorimetry (TOPEM-DSC). The results confirm that there is successful emulsion copolymerization between modified EPAC oligomer and acrylate monomer. TEM show that the particles of epoxy-acrylate composite have a core-shell structure, and there is no free epoxy resin. The FTIR and TOPEM-DSC results reveal that the copolymer emulsion possesses self-crosslinking ability. During film formation, self-crosslinking reaction occurs between epoxide groups with carboxyl groups, giving exothermal phenomena. The thermal stability as well as the corrosion resistance of the films was analyzed. The results show outstanding thermal stability as well as corrosion resistance attributable to the crosslinking reticulation structure. It is envisaged that the epoxy-acrylate composite latex has great potential in the development of high-performance aqueous coatings.     

丁苯乳液共聚合动力学的研究

本文详细考察了高转化率下各种因素对丁苯乳液共聚合速率的影响。以过硫酸钾为引发剂,岐化松香皂和硬脂酸钾的混合物为乳化剂,正十二硫醇为链转移剂,在5升不锈钢高压釜中进行了丁苯乳液共聚合实验。随着乳化剂和引发剂浓度的增大、乳化剂中硬脂酸钾相对量的增加以及温度的升高,聚合速率均加快;加入少量电解质可以提高聚合速率;加入少量硫醇与完全不加硫醇相比,聚合速率有很大提高。另外,还发现氧对聚合有明显的阻聚作用、水油比对单体转化速率影响不大。同时理论推导了乳胶粒数随时间的变化关系,并在自由基聚合机理,乳胶粒中单体浓度连续下降等假设的基础上推导了高转化率下乳液聚合的数学模型,对于丁二烯、苯乙烯共聚体系,模型计算值与实验值能较好的吻合。     

Studies of water-soluble oligomers formed in emulsion copolymerization

A polymer chain transfer agent was synthesized by the reaction between poly(vinylbenzyl chloride) latex particles and 2-aminoethanethiol in a basic environment. In subsequent emulsion polymerization reactions, low molecular weight species were formed when waterborn oligomeric radicals diffused to the surface of these seed particles. These low molecular weight oligomers were separated by membrane filtration and their composition and molecular weight weight were analyzed by FTIR and mass spectroscopy. The measured composition results were compared with those that were calculated from the copolymerization equation. The molecular weights were compared with earlier experimental results that were obtained by isolation of oligomers formed when a water-soluble inhibitor was added to a reacting emulsion. Three seeded emulsion copolymerization systems, that is, styrene–acrylic acid, styrenemethacrylic acid, and styrene–methyl methacrylate, were investigated. The distribution of monomer in the water phase and in the copolymer particles was analyzed. The results show that the oligomer compositions for different copolymerization systems can be approximated reasonable well by the copolymerization equation, using the reactivity ratios obtained from bulk copolymerization. The length of the oligomer radicals formed depends on their composition and the properties of the polymer particles, such as surface charge, composition, size, and concentration. © 1994 John Wiley & Sons, Inc.     

The influence of monomer types on the colloidal stability in the miniemulsion copolymerization involving alkoxysilane monomer

Unlike conventional emulsion polymerization, monomer droplet nucleation becomes dominant in miniemulsion polymerization, offering the miniemulsion polymerization a great advantage over conventional emulsion polymerization when incorporating alkoxysilane monomer, which can easily undergo premature hydrolysis and condensation reactions, into polymer latex. The extensive premature hydrolysis and condensation can lead to the issue of the colloidal instability. In this article, the influence of monomer types on the colloidal stability in the miniemulsion co-(or ter-)polymerization was investigated when incorporating alkoxysilane monomer into styrene or acrylate latex. In the cases of butyl acrylate (BA)/γ-methacryoxypropytrimethoxysilane (MPMS), BA/methyl methyacrlate (MMA)/MPMS, and BA/styrene (St)/MPMS miniemulsion polymerization, nearly no coagulum was observed. The obtained latex had a long shelf life. However, the coagulum was formed in the late stage of MMA/MPMS and St/MPMS miniemulsion copolymerization. The shelf life of the corresponding latex was short. The selection of the main monomer, which can fast consume alkoxysilane comonomer, was critical to obtain the stable latex. In this way, the alkoxysilane groups were completely buried in particles thus the coagulation caused by condensation reactions derived from the alkoxysilane hydrolysis among particles was suppressed.     

醋酸乙烯-丙烯酸无皂乳液共聚的研究

研究了以醋酸乙烯(VAc)为主单体,丙烯酸(AA)为改性功能单体,以“半连续”加料方式进行无皂乳液共聚合过程,得到了稳定的乳液。并探讨了功能单体AA含量、反应温度等对共聚的影响。采用FTIR、粒度分析等方法对共聚物的组成、乳胶粒子的尺寸及分布进行了分析表征。结果表明:在(65±2)℃的温度下聚合,所得乳液稳定性好、转化率高,反应完全,且随着功能单体AA含量的增加,乳液粘度上升,单体转化率下降,乳胶粒粒径变小且粒径呈单分散性。     

Preparation and characterization of imidazole‐functionalized microspheres

The preparation of imidazole‐functionalized latex microspheres by a two‐stage emulsion copolymerization process and their characterization are reported on. Emulsifier‐free emulsion copolymerization of styrene (St) and 1‐vinyl imidazole (VIMZ) exhibited bimodal particle size distributions caused by secondary homogeneous nucleation process. However, secondary nucleation can be avoided by using cetyltrimethylammonium bromide (CTAB) as a stabilizer at a concentration below its cmc (critical micelle concentration). This would result in the formation of monodisperse latex particles. The final particle size diameter depended on the concentration of CTAB as well as the amount of VIMZ. To control the amount of the functional imidazole groups on the latex particle surfaces, independent of the latex diameters, without secondary nucleation of particles, the seeded emulsion copolymerization of styrene and VIMZ was explored as a second‐stage polymerization at different concentrations and ratios of monomers in the presence of the previously prepared monodisperse poly(styrene‐co‐1‐vinyl imidazole) seed latex particles. The concentration of imidazole functional groups on the surface of the latex particles could also be varied through the rearrangement of hydrophilic imidazole groups by varying the second‐stage monomer addition process such as the utilization of monomer‐swollen seed particles or a shot addition of monomers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 120:5753–5762, 2006     

Film formation and mechanical properties of the alkoxysilane-functionalized poly (styrene-co-butyl acrylate) latex prepared by miniemulsion copolymerization

Alkoxysilane-functionalized poly (styrene-co-butyl acrylate) latex was prepared via miniemulsion copolymerization of γ-methacryloxypropyltrimethoxysilane (MPS), styrene and butyl acrylate using AIBN at neutral condition. The effects of initiator types, pH values, and MPS contents on the premature cross-linking of the latex particles and the mechanical properties of the films were investigated by the swelling experiments and dynamic mechanical analysis. It was found that the storage modulus of the latex films and the glass transition temperature (T_g) increased with increasing MPS content. The acidification of latex prior to film formation and annealing the latex films could improve the mechanical properties of the films.