Oil core/polymer shell microcapsules by internal phase separation from emulsion droplets. II: controlling the release profile of active molecules.
Oil core/polymer shell microcapsules by internal phase separation from emulsion droplets. II: controlling the release profile of active molecules.
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DOI：
10.1021/la0470838
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发表时间：
2005-05
期刊：
影响因子：
--
通讯作者：
P. Dowding;R. Atkin;B. Vincent;P. Bouillot
中科院分区：
文献类型：
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作者：
P. Dowding;R. Atkin;B. Vincent;P. Bouillot
通过从水包油乳液的内相中沉淀聚合物，制备了具有油核和固体聚合物壳的微胶囊。分散相由聚合物、聚合物的良溶剂（二氯甲烷）和聚合物的不良溶剂（十六烷）组成。去除良溶剂导致乳液液滴内聚合物的相分离，导致在不良溶剂周围形成聚合物壳。在乳化之前将UV活性有机分子加入油相中。如果该分子具有一定的水溶性，则可以确定该分子从胶囊中的释放曲线。虽然微胶囊的大小保持大致恒定，广泛的因素对释放曲线的影响进行了研究。这些因素包括成壳聚合物的类型和分子量、活性成分分子的分子量、壳厚度、使用共聚物或聚合物共混物形成壳、交联壳或在壳形成后将胶囊加热至高于聚合物的T（g）值的温度的效果，以及在使用弱交联剂作为壳聚合物的情况下释放溶液的pH变化的影响。行为的差异进行了讨论的聚合物壳的性质，特别是厚度，聚合物/释放分子的相互作用，和自由体积/孔隙率。这些参数的变化允许控制最终释放产率和释放速率，持续几小时至几天的时间段。
Microcapsules with oil cores and solid polymer shells have been prepared by precipitation of the polymer from the internal phase of an oil-in-water emulsion. The dispersed phase consists of a polymer, a good solvent for the polymer (dichloromethane), and a poor solvent for the polymer (hexadecane). Removal of the good solvent results in phase separation of the polymer within the emulsion droplet, leading to the formation of a polymeric shell surrounding the poor solvent. A UV-active organic molecule is added to the oil phase prior to emulsification. Provided this molecule has some water solubility, the release profile of the molecule from the capsule can be determined. While the microcapsule size was kept approximately constant, the influence of a wide range of factors on the release profile has been studied. These include the type and molecular weight of the shell-forming polymer, the molecular weight of the active ingredient molecule, the shell thickness, the use of copolymers or polymer blends to form the shell, the effect of cross-linking the shell or heating the capsule to temperatures above the T(g) value of the polymer after the shell has been formed, and the effect of changes in the pH of the release solution in the case when a weak polyelectrolyte is used as the shell polymer. The differences in behavior are discussed in terms of the properties of the polymer shell, in particular the thickness, the polymer/release molecule interaction, and the free volume/porosity. Variation of these parameters allows one to control both the final release yield and the rate of release for time periods between a few hours and days.