Division of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8563, Japan.
J Phys Chem B. 2011 Dec 1;115(47):13828-34. doi: 10.1021/jp208056b. Epub 2011 Nov 4.
Hollow microcapsules of poly(lactic acid) (PLA) were fabricated using the bubble template method, which involves the nucleation of bubbles inside droplets of a dichloromethane solution of PLA prepared in a continuum medium of an aqueous solution of poly(vinyl alcohol) (PVA). PLA-covered microbubbles are formed by PLA adsorbing onto the microbubble surface and then spontaneously released from the dichloromethane droplets into the surrounding aqueous solution. Thereby, hollow PLA microcapsules are formed. In the present study, we focus on the effects of the initial PLA concentration, addition of PVA to the aqueous medium, and PLA molecular weight on the radius distribution of the hollow PLA microcapsules. Results show that a low initial concentration of PLA, the addition of PVA, and low molecular weight PLA are required to form uniform hollow microcapsules. It is suggested that these factors reduce the energy barrier at the liquid-liquid interface, which allows the PLA-covered microbubbles to pass smoothly through the interface. Furthermore, we observed the release of the microbubbles from the dichloromethane droplets through a microscope and clarified the relationship between the uniformity of the hollow PLA microcapsules and the bubble-release mechanism.
聚乳酸（PLA）的中空微胶囊是通过气泡模板法制备的，该方法涉及在聚（乙烯醇）（PVA）水溶液连续介质中制备的 PLA 的二氯甲烷溶液液滴内成核气泡。PLA 通过吸附到微气泡表面并从二氯甲烷液滴自发释放到周围水溶液中，形成 PLA 覆盖的微气泡。由此，形成中空 PLA 微胶囊。在本研究中，我们重点研究了初始 PLA 浓度、向水介质中添加 PVA 以及 PLA 分子量对中空 PLA 微胶囊半径分布的影响。结果表明，形成均匀中空微胶囊需要低初始 PLA 浓度、添加 PVA 和低分子量 PLA。这表明这些因素降低了液-液界面的能垒，从而使 PLA 覆盖的微气泡能够顺利通过界面。此外，我们通过显微镜观察了微气泡从二氯甲烷液滴中的释放，并阐明了中空 PLA 微胶囊的均匀性与气泡释放机制之间的关系。
