Synthesis of hydrophobic-hydrophilic gradient gel and its application

本研究报道了将聚丙烯酸凝胶（DAA）外层DBU盐与烷基卤化物酯化合成疏水-亲水性梯度凝胶，得到聚丙烯酸凝胶与疏水壳层化学覆盖结合的新型两亲性核-壳型凝胶。当凝胶放置在含有过量烷基卤化物的非质子极性溶剂中时，会发生膨胀，凝胶分为膨胀的壳和未膨胀的核。当R和R分别为t min后的壳半径和核半径时，反应凝胶与原始凝胶的表观比作为R /R的函数。以r/ r为函数，采用齐次模型进行动力学分析。整个反应由烷基卤化物通过膨胀壳的扩散速率、酯化速率和烷基卤化物通过未膨胀核的扩散速率组成。有三个控制利率的步骤；扩散通过膨胀壳控制，酯化控制，扩散通过未膨胀核心控制。烷基卤化物的易读性和体积对反应有明显影响。此外，热酸催化的聚甲基丙烯酸丁酯凝胶从内部脱酯化得到类似的核-壳型凝胶。基于这一背景，我们制备了凝胶胶囊。当将含有化学物质的凝胶胶囊浸入溶液中时，化学物质会随着凝胶的膨胀而释放。结果表明，凝胶胶囊的化学释放受壳层厚度和化学结构的控制。因此，所制备的凝胶胶囊具有控释作用。

This study reports novel synthetic of hydrophobic-hydrophilic gradient gradient gel by the esterification of outer DBU salt of poly (acrylic acid) gel (DAA) with alkyl halide to give new amphiphilic core-shell typed gel which is poly (acrylic acid) gel covered and bound chemically with hydrophobic shell layr. When the gel was placed in an aprotic polar solvent containing excess alkyl halide, swelling occurred and the gel was divided into a swollen shell and an unswollen core. When R and r are radius of shell and core after t min, respectively, the apparent ratio of reacted gel to the original gel was determined as function of r/R.The rection was followed as a function of r/R and analyzed kinetically using homogenous model. The overall reaction consisted of rates of diffusion of alkyl halide through swollen shell, esterification, and diffusion of alkyl halide through unswollen core. There are three rate-controlling steps ; diffusion through swollen shell control, esterification control, diffusion through unswollen core control. The reaction was affected markedly by readctivity and bulkiness of alkyl halide. Furthermore, the thermal acid-catalyzed deesterification of poly (t-butyl methacrylate) gel from the inner gives similar core-shell typed gel. We prepared gel casules based on this background. When the gel capsules containing chemicals were dipped in solution, the release of chemical took place with swelling the gels. This results suggested that the chemical release from the gel capsule controlled by the thickness of the shell layr and chemical structures. Therefore, the obtained gel capsule is useful for control release.