Preparation of Functional Microcapsules Consisting of Porous Polymer as Shell Material

以硬脂酸为核心材料，在苯乙烯单体浓度为2 ~ 6 mol/l，反应器转速为200 ~ 600 rpm的条件下，原位聚合法制备了具有温度依赖性释放速率的聚苯乙烯微胶囊。在293 ~ 343 k的温度范围内，对微胶囊的释放速率进行了测量，结果如下：1)单体浓度对微胶囊大小的影响较小，即随着单体浓度的增加，微胶囊大小减小。这可能是由于粘度随单体浓度的降低而降低，并且在较短的反应时间内从相分离中较快地形成聚合物外壳。2)在相同温度下，微胶囊的渗透系数随单体浓度A_0的增加而降低。这与许多原位聚合制备的微胶囊的渗透性相同。当A_0 = 2 mol/l时，得到了单位核微胶囊；当A_0 = 4 mol/l时，得到了包含许多聚苯乙烯微珠的微胶囊；当A_0 = 6 mol/l时，得到了多孔或多核微胶囊。3) 75 ^ C下硬脂酸的释放速率是40^ C下的15倍左右，因此很有可能制备出可随温度变化控制释放速率的功能性微胶囊。

To obtain the functional microcapsules with a temperature-dependent release rate using in situ polymerization polystyrene microcapsules containing stearic acid as core material were prepared under the conditions of styrene monomer concentration = 2 - 6 mol/l and revolution rate of reactor paddle = 200 - 600 rpm. The following results were obtained from the release rate measurements with changing temperatures in the range of 293 - 343 K.1) A small effect of monomer concentration on microcapsule size was observed, that is, microcapsule size decreased with increasing monomer concentration. This would be due to that the viscosity decreases with monomer concentration and the comparatively rapid formation of polymer shell occurs from the phase separation in a short reaction time.2) The permeability coefficient of microcapsules decreased with increasing monomer concentration A_0 at the same temperature. This is the same as the permeability of many microcapsules prepared by in situ polymerization. Unit nuclear microcapsules were obtained for A_0 = 2 mol/l, microcapsules including many minute polystyrene beads for A_0 = 4 mol/l, and porous or multi-nuclear microcapsules for A_0 = 6 mol/l.3) Release rate of stearic acid at 75 ^ﾟC is about 15 times of that at 40^ﾟC, so the functional microcapsules, of which release rate us controlled with changing temperature, will be available with high possibility.