Synthesis of hydrophobic-hydrophilic gradient gel and its application

本研究报道了一种新型的疏水-亲水梯度凝胶的合成方法，该方法是将聚丙烯酸凝胶(DAA)的外层DBU盐与卤代烷基化合物进行酯化反应，得到一种新型的两亲性核壳型凝胶，该凝胶是以疏水壳层为化学包覆层的聚丙烯酸凝胶。当凝胶放置在含有过量卤代烷的非质子极性溶剂中时，凝胶发生膨胀，凝胶分为膨胀的壳和未膨胀的核。当R和r分别为tmin后的壳层半径和芯层半径时，确定了反应凝胶与原始凝胶的表观比为r/R的函数，并用均质模型进行了动力学分析。整个反应包括卤代烃通过膨胀的壳层的扩散速率、酯化反应和卤代烃通过未膨胀的核的扩散速率。有三个速率控制步骤：膨胀壳扩散控制、酯化控制、未膨胀核扩散控制。卤代烷基化合物的可读性和膨胀性对反应有显著影响。此外，聚甲基丙烯酸叔丁酯凝胶的热酸催化从内部脱酯得到了类似的核壳型凝胶。基于这一背景，我们制备了凝胶型干酪。当含有化学物质的凝胶胶囊浸入溶液中时，化学物质的释放伴随着凝胶的膨胀而发生。这一结果表明，凝胶胶囊的化学释放受壳层厚度和化学结构的控制。因此，所获得的凝胶胶囊可用于控释。

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.