Preparation of Functional Microcapsules Consisting of Porous Polymer as Shell Material

为获得具有温度依赖释放速率的原位聚合功能微胶囊，以硬脂酸为芯材，在苯乙烯单体浓度为2~6mol/L，反应桨转速为200~600rpm的条件下制备了聚苯乙烯微胶囊。在293-343K1)温度范围内，微囊的释放速率随温度的变化而变化。1)单体浓度对微囊尺寸的影响不大，即微囊尺寸随单体浓度的增加而减小。这是由于微胶囊的粘度随单体浓度的增加而降低，在较短的反应时间内发生相分离而形成较快的壳层。2)在相同温度下，微胶囊的渗透系数随单体浓度A_0的增大而减小。这与许多原位聚合法制备的微胶囊的渗透性相同。当A_0=2m ol/L时，可得到单位核微囊；当A_0=4m o l/L时，可制得含有大量微珠的微囊；当A_0=6m o l/l时，可制得多孔或多核微囊。3)硬脂酸在75ﾟC时的释放率约为40ﾟC时的15倍，因此很有可能获得释放度随温度变化的功能性微囊。

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.