中空聚合物微球的制备Ⅰ．无胶束乳液聚合制种子乳胶粒

为了制得具有中空结构的聚合物微球，首先以十二烷基苯磺酸钠（SDBS）为乳化剂，在其用量低于CMC的条件下，进行甲基丙烯酸甲酯、甲基丙烯酸和丙烯酸丁酯的乳液聚合，制备了带羧基的种子乳液。以种子乳液为基础可通过核壳乳液聚合和适当的碱处理制得具有中空结构的聚合物微球。采用粒度仪和TEM测定了乳胶粒的直径及其分布，采用TEM和ESEM对乳胶粒结构形态进行了表征。研究了种子制备过程中单体加料方式、乳化剂用量及反应温度等对聚合稳定性、种子乳胶粒直径及其分布的影响，确定了制备种子乳胶粒的最佳工艺条件。当SDBS用量为单体总量的0．5％，采用一次性加入单体的进料工艺，反应温度为80℃时，可以得到粒径为140nm，且粒径呈单分散分布的种子乳胶粒。     

乳液聚合法制备中空乳胶粒的研究

采用多段乳液聚合法制备了聚(甲基丙烯酸甲酯-丙烯酸正丁酯-甲基丙烯酸)/聚(苯乙烯-丙烯腈)核壳乳液,然后用碱溶胀处理得到了单分散性较好的中空聚合物微球.以透射电子显微镜(TEM)和扫描电子显微镜(SEM)对各阶段乳液聚合的胶粒大小和分布以及形貌行了表征.研究了种子乳液聚合反应时间、搅拌速度、单体滴加速度等因素对中空聚合物微球的形态及粒径分布的影响.结果表明:当单体的滴加速度控制在0.1～0.2g/min,搅拌速度控制在80～120 r/min时,可以制备中空形态较好的中空聚合物微球.     

中空聚合物微球的制备——种子及核乳胶粒的制备

为了制得具有中空结构的聚合物微球,首先以十二烷基苯磺酸钠(SDBS)为乳化剂,在其用量低于CMC的条件下,进行甲基丙烯酸甲酯(MMA)、甲基丙烯酸(MAA)和丙烯酸丁酯(BA)的乳液聚合,制备了带羧基的种子乳胶粒.然后采用MMA、MAA和二乙烯基苯为单体进行种子乳液聚合,制备了轻度交联的带羧基的核乳胶粒.该核乳胶粒经过核-壳乳液聚合和适当的碱处理工艺就可成为具有中空结构的聚合物微球.采用粒度仪测定了乳胶粒的直径及其分布,采用TEM对乳胶粒结构形态进行了表征.研究了种子及核乳胶粒制备过程中单体加料方式、乳化剂用量及羧基单体种类等因素对聚合稳定性、乳胶粒直径及其分布以及最终的中空聚合物微球结构形态的影响,确定了制备种子及核乳胶粒的最佳工艺条件.在制备种子阶段,SDBS用量为单体总量的0.5%,采用一次性加入单体的进料工艺;在核乳胶粒制备阶段,以MAA为羧基单体,所有单体采用"饥饿式"加料,半连续补加乳化剂并使乳化剂用量为核单体总量的0.15%时可保持聚合稳定性并保证无新乳胶粒生成.     

环氧树脂改性核壳乳胶粒子的制备

采用预乳化-半连续种子乳液聚合工艺制备了环氧树脂改性聚丙烯酸丁酯/(聚甲基丙烯酸甲酯-衣康酸)(PBA/P(MMA-ITA-DGEBA))核壳乳胶粒子。采用激光粒度仪、傅立叶变换红外光谱(FTIR)、差示扫描量热仪(DSC)、透射电子显微镜(TEM)等方法对核壳乳胶粒子进行了表征,实验结果表明:PBA/P(MMA-ITA-DGEBA)乳胶粒子确为核壳结构,双酚A型环氧树脂已经被成功接枝到核壳乳胶粒子上,由于ITA、DGEBA链段的存在,导致壳层PMMA玻璃化转变温度的(Tg)升高。     

丙烯酸类中空聚合物粒子的制备与电泳性能

以甲基丙烯酸甲酯、丙烯酸丁酯、α-甲基丙烯酸和苯乙烯为单体,以过硫酸钠为引发剂,温度控制在78℃,搅拌速度为800 r/min,采用半连续加料法,经乳液聚合分别制得了种子、核及具有核壳结构的聚合物粒子。用动态光散射(DLS)、原子力显微镜(AFM)、扫描电镜(SEM)测得其平均粒径分别为72.1、400及500 nm。核壳粒子用w(NaOH)=10%的水溶液进行溶胀,得到的粒子经透射电子显微镜(TEM)显示为中空结构,在SEM下观察,其平均粒径在900 nm左右。用微电泳仪测得,该中空粒子在四氯乙烯分散介质中电泳淌度为0.004 98 s2.mA.kg,Zeta电位为0.032 2 mV,在水分散相中,Zeta电位为-43.880 mV。     

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。     

室温可自成膜中空微球乳液的制备

在低皂体系中，采用程序加料方式，连续制备了带有羧基的种子、核乳胶粒，然后通过包覆具有交联结构的中间层及成膜性良好的聚合物壳，最后缓过碱处理，得到了可以自成膜的中空聚合物微球。这种中空聚合物微球不仅仅可以作为涂料的遮盖剂，而且可单独使用，提高涂层的遮盖力。     

中空聚合物乳胶粒的制备

研究了在制备中空聚合物乳胶粒过程中，甲基丙烯酸用量、乳化剂用量对最终中空乳胶粒粒径、空径的影响。实验结果表明，甲基丙烯酸用量为单体量的30％，乳化剂在核层以及壳层制备过程中用量分别为单体量的0．15％和0．2％时，能得到粒径均一、空径最大的中空乳胶粒。     

不对称P(St-co-AA)/PS乳胶粒子的研制

不对称的乳胶粒子属于Janus粒子的范畴,而Janus粒子是近年发展起来的一种具有独特性质的粒子.Janus粒子表面物理或化学性质不同,其在催化、光学、材料、生物传感、生物医药及电子学等领域具有广阔的应用前景.本研究用乳液聚合法合成不对称P(St-co-AA)/PS乳胶粒子,并从热力学和动力学角度探索了反应温度、引发剂...     

室温可自成膜中空微粒乳液的制备

采用羧基单体进行多阶段的种子乳液聚合,制备了内核为带羧基的聚合物、最外层为易成膜的低玻璃化温度聚合物、中间为轻度交联中间隔离层的多层核壳结构乳胶粒,最后通过碱处理制成了具有室温成膜性的中空结构聚合物微粒。研究表明,在反应前期以十二烷基苯磺酸钠为乳化剂,包壳阶段同时加入OP-10可有效控制乳胶粒结构形态,同时提高聚合物乳液的电解质稳定性;以甲基丙烯酸为羧基单体,其用量为核单体总量的30%(质量分数)时,聚合物微粒中空直径较大且微粒结构规整;碱处理温度以100℃为宜。在优化的工艺下,制得的室温可成膜中空聚合物微粒外径约500 nm,中空直径约300 nm。     

Preparation and structure control of hollow polymer particles: Influence of seeded emulsion polymerization and alkalization treatment process

Hollow polymer latex particles containing a hydrophilic core were prepared by seeded emulsion polymerization with MAA/BA/MMA/St as comonomers, followed by stepwise alkalization treatment with ammonia. The size and morphology of composite latex particles was determined by TEM. The effects of the seeded emulsion polymerization conditions and alkalization treatment on the size and hollow structure of latex were investigated. The results showed that the optimum content of crosslinking agent in the shell polymers was about 0.5–1.0 wt %, emulsifier was about 0.8–1.1 wt %, and the core/shell weight ratio was 1/7. To obtain uniform hollow latex particles with large size, the starved feeding technique should be adopted in seeded emulsion polymerization, and the neutralization temperature should equal to the T_g of the shell polymer. Then, the obtained polymer particles under this condition had an excellent hollow structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Enhancing formation and retention of hollow structural integrity through intermediate and outermost layer design in seeded emulsion polymerization of hollow latex particles

The synthesis of hollow latex particles through seeded emulsion polymerization involves a series of intricate steps, including the formation of distinct polymer layers with specific properties. Despite extensive research, preserving the desired hollow structure remains challenging due to the unclear role of the encapsulating polymer layers. This study systematically adjusts the glass transition temperature (T_g) of the intermediate layer by varying the butyl acrylate (BA) ratio in the monomer feed mixture. By controlling the reaction temperature during alkali swelling, we explore the critical influence of T_g on hollow latex particle formation from carboxylated core latex particles. To ensure long-term hollow structure retention after drying, a rigid outer layer is polymerized onto the intermediate layer. Surprisingly, higher divinylbenzene (DVB) mass ratios (5.0 and 10.0 wt%) do not result in a highly crosslinked hollow shell due to DVB self-nucleation. This paper emphasizes the importance of precise design parameters for both intermediate and outermost layers in achieving and maintaining hollow latex particle structures. Understanding each layer's role and optimizing their compositions contribute to advancing hollow latex particle synthesis through seeded emulsion polymerization.     

具有核壳结构的聚合物粒子

概述了具有核壳结构的聚合物粒子的制备方法、形成条件及形成机理,介绍了它们在作为高分子材料的抗冲击改性剂和增韧剂、涂料和粘合剂等领域的应用,并对这一领域的发展进行了展望。     

聚苯乙烯-聚甲基丙烯酸甲酯核-壳粒子的制备

由种子乳液聚合法制备了聚苯乙烯-聚甲基丙烯酸甲酯核-壳粒子。以过硫酸钾(KPS)为引发剂,辛基酚聚氧乙烯醚(OP-10)为乳化剂,合成了聚苯乙烯(PS)种子核;连续滴加甲基丙烯酸甲酯(MMA),在核表面富集MMA,制备了粒径范围在0.16~0.67μm的核-壳粒子;当单体苯乙烯与甲基丙烯酸甲酯(St/MMA)的比为30∶70(质量比)时,所得粒径在0.18μm,粒径分布为0.012。差示扫描量热(DSC)研究显示,复合粒子的玻璃化转变温度(Tg)为97.2℃,峰形单一,表现出良好的热性能。     

Development of morphology in latex particles: The interplay between thermodynamic and kinetic parameters

A thermodynamic analysis and a mathematical model were developed to describe the free energy changes corresponding to various possible morphologies in composite latex particles. Two experimental composite latex systems were used to verify and establish limitations of the model. The two latex systems were based on polystyrene/poly(methyl methacrylate), one prepared by conventional seeded emulsion polymerization and the second system by direct emulsification of a solution of a blend of the two polymers. The influence of several experimental parameters on latex particle morphology was investigated. These included monomer/polymer ratio, surfactant type, and initiator type in the seeded emulsion polymerization system. The influence of local viscosity, shear effects, and molecular weights of polymers were investigated in the artificial latex system.     

Morphology control of hollow polymer latex particle preparation

Hollow polymer latex particles containing a hydrophilic core fully encapsulated with a hydrophobic shell were prepared by multistage polymerization followed by neutralization with a base. The diameters of the particles were monodispersed and void fractions of the prepared latex particles as high as 50% were achieved. High instantaneous monomer conversion was found to be the key point to minimize the interdiffusion of the core–shell polymer chains. The influences of the shell crosslinking agent and shell carboxyl content on the hollow morphology were also investigated. The maximum hollow diameter was observed with crosslinking agent contents of 7.5–12.5 wt %. The shell carboxyl content had an appropriate value, and an excess of it resulted in an excentric hollow structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 860–863, 2005     

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     

Core–shell latex particles consisting of polysiloxane–poly(styrene-methyl methacrylate-acrylic acid): Preparation and pore generation

Latexes with a poly(dimethyl siloxane) core and a poly(styrene-methyl methacrylate-acrylic acid) [poly(St-MMA-AA)] shell have been prepared in two steps in order to generate particles that have a core with a very low glass transition temperature. In the first step, poly(dimethyl siloxane) particles were obtained via the ring-opening emulsion polymerization of octamethyl tetracyclosiloxane (D₄). The polymerization was carried out using either an anionic or a cationic catalyst. In the first case, sodium hydroxide was used as catalyst and sodium dodecylbenzene sulfonate as surfactant, while in the second, the alkylbenzene sulfonic acid (ABSA) was used both as catalyst and surfactant. Using a PD₄ latex as seed, a seeded emulsion polymerization of St-MMA-AA was conducted to obtain PD₄–P(St-MMA-AA) core–shell particles. Numerous recipes were attempted and the most successful were those in which the seed was prepared with a cationic catalyst (ABSA) at a relatively low temperature (75°C). The core–shell structure of the particles was identified by transmission electron microscopy, but also via wetting angle, water absorption, and T_g measurements. Finally, pores were generated in the core–shell particles via an alkali–acid treatment. Because PD₄ has a very low glass transition temperature, it cannot be easily handled. However, protected by a shell, it could be used as a constituent of composite materials with enhanced impact strength, even at very low temperatures. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2235–2245, 1999     

Prediction and experiment of core–shell particle morphology of vinyl acetate and butyl acrylate

In this article, the particle morphology in emulsion polymerization of the poly(vinyl acetate) (PVAc)/poly(butyl acrylate) (PBA) system is investigated. With the use of the basic data in literature, the relevant interface tensions and viscosity are estimated with the equation proposed in literature. The time achieved to equilibrium morphology is predicted with cluster dynamics proposed by Gonzalez. The experiment result is consistent with that of prediction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2930–2937, 2002; DOI 10.1002/app.10297