Loxley A, Vincent B
School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, United Kingdom
J Colloid Interface Sci. 1998 Dec 1;208(1):49-62. doi: 10.1006/jcis.1998.5698.
Particles with liquid cores and solid shells have been prepared by the controlled phase separation of poly(methylmethacrylate) (PMMA) within the droplets of an oil-in-water emulsion. The oil phase of the emulsion contained poly(methylmethacrylate), a good solvent for the polymer (CH2Cl2), a poor solvent (hexadecane, decane, octanol, or tetrachloromethane), and in some cases acetone (a water soluble co-solvent) to aid emulsification. Emulsions were prepared using a Silverson high-speed stirrer, and the droplet size distributions were determined using a Coulter particle counter. Size distributions were found to be dependent on the nature of the emulsifier, the concentration of acetone in the oil phase, and the concentration of polymer in the oil phase. The good solvent was then removed under reduced pressure, causing the poly(methylmethacrylate) to phase separate within the emulsion droplets. The resultant two-phase particles were characterized by optical microscopy and scanning electron microscopy. Particle morphologies depended strongly on the nature of the non-solvent and also the emulsifier employed. Spreading coefficients were calculated from interfacial tension and contact angle measurements, and were used to account for the morphologies observed. Core/shell microcapsules were formed when hexadecane or decane was used as non-solvent, and only when polymeric emulsifiers were employed. All other combinations yielded "acorn"-shaped particles. The thickness of microcapsule walls was found to be a constant fraction of the overall capsule diameter for all microcapsule sizes and depended, as expected, on the concentration of polymer in the oil phase. Copyright 1998 Academic Press.
通过聚甲基丙烯酸甲酯（PMMA）在水包油乳液液滴内的可控相分离制备了具有液核和固壳的颗粒。乳液的油相中含有聚甲基丙烯酸甲酯、该聚合物的良溶剂（二氯甲烷）、不良溶剂（十六烷、癸烷、辛醇或四氯化碳），并且在某些情况下含有丙酮（一种水溶性共溶剂）以辅助乳化。使用Silverson高速搅拌器制备乳液，并使用库尔特颗粒计数器测定液滴尺寸分布。发现尺寸分布取决于乳化剂的性质、油相中丙酮的浓度以及油相中聚合物的浓度。然后在减压下除去良溶剂，使聚甲基丙烯酸甲酯在乳液液滴内发生相分离。通过光学显微镜和扫描电子显微镜对所得的两相颗粒进行表征。颗粒形态强烈依赖于非溶剂的性质以及所使用的乳化剂。根据界面张力和接触角测量计算铺展系数，并用于解释所观察到的形态。当使用十六烷或癸烷作为非溶剂时，并且仅当使用聚合物乳化剂时，形成核/壳微胶囊。所有其他组合产生“橡子”形颗粒。发现对于所有微胶囊尺寸，微胶囊壁的厚度是总胶囊直径的恒定分数，并且如预期的那样，取决于油相中聚合物的浓度。版权所有1998年学术出版社。
