【作者】 李晓东；

【导师】 沈家骢； 胡巧玲；

【作者基本信息】 浙江大学 ， 材料学， 2006， 博士

【摘要】 基于LBL技术，制备聚电解质微胶囊，由于其制备方便，囊壁厚度、组成、性质的可控性，越来越引起了广大科研人员的兴趣。但是，由于其囊壁的通透性良好，对水溶性物质的高效包埋一直是这个领域的难点。本论文针对这些问题，提出了功能型模板的新概念，这种功能型的模板可以在模板除去后，二次修饰囊壁，改变囊壁的通透性；同时，利用预留于胶囊内部的特殊物质作为驱动力，高效的诱导包埋水溶性物质。首先利用大分子两亲嵌段共聚物PS-b-PAA形成的胶束作为模板控制合成尺寸可控的杂化碳酸钙模板，通过研究在试验条件下钙离子对胶束在碱性环境中的聚集形态，利用TEM得到了直接的关于胶束聚集形态的试验证据，系统的研究发现，在试验条件下胶束可以形成球形的聚电解质的网络状结构，控制合成杂化粒子的形貌。深入的研究发现，这种杂化粒子具有很强的耐酸性，在成功解释它的耐酸性机理后，发现了它的溶解条件。以这种杂化粒子为模板，利用LBL技术，分别采用不同种类的聚电解质(根据组装的中性条件下，聚电解质的电荷密度将其分为强电解质和弱电解质)制备了聚电解质胶囊。激光共聚焦(CLSM)，电子扫描显微镜(SEM)和原子力显微镜(DFM)证实了这种胶囊球形良好、分散良好，同时，囊壁厚而致密。显然，大分子胶束被成功的预留于胶囊内部。利用激光共聚焦研究这种胶囊的包埋行为发现，它能够高效包埋水溶性的正电荷物质。对其动力学研究发现，胶囊对正电荷物质的包埋速度具有分子量依赖性，随着分子量的增加，包埋速度降低，但是，对最后的包埋总量影响不大。对其囊壁的结构研究，证实了这种胶囊是有聚电解质层和胶束层组成的双层结构，其中胶束层对其包埋行为的控制具有关键性的作用。对包埋了不同电荷性质、不同分子量物质的聚电解质胶囊在不同pH条件和不同盐离子浓度下的释放研究发现，这种胶囊对不同分子量、不同电荷性质的物质的释放行为有一定的差别。对小分子正电荷物质和中性物质的药物释放率较高，但是载药量较低。当被包埋物带强的正电荷时往往导致胶囊的载药量大大增加，但是也导致胶囊总的药物释放率过低。试验还发现，胶囊对于牛血清蛋白(BSA)具有较好的缓释作用。这种聚电解质胶囊的囊壁的双层结构是影响其包埋物释放速度的关键因素，同时，被包埋物的分子量和电荷性能也强烈的影响了胶囊的释放行为。更多还原

【Abstract】 Layer-by-layer (LBL) assembly of oppositely charged polyelectrolytes onto removable colloidal particles might be the most widely employed technique to prepare novel hollow nano- and microcapsules. This fabrication technique allows control of the capsule size and shape, the capsule wall thickness, and the capsule wall composition. Microcapsules with versatile properties can be obtained by introducing one or more functional components such as nanoparticles, biomacromolecules, lipids, photosensitive dyes, inorganic crystals, and multivalent ions onto the capsule wall or into the capsule interior. However, it is difficult for polyelectrolyte capsule to encapsulate water-soluble substances due to high permeability of the capsule shell. In this paper, a novel hybrid calcium carbonate microparticle was synthesized to serve as template to fabricate polyelectrolyte capsule by LBL technique. After the templates were removed, the capsule shell was tailored by the substances in template which was intentionally retained in capsule. At the same time, the retained substances serve as a driving force to entrap water-soluble substances into capsule interior with high efficiency. The novel hybrid template was named as functional template.Hybrid calcium carbonate microparticles were synthesized in the presence of block copolymer PS-b-PAA which served as three-dimensional templates. It’s found that the PS-b-PAA based micelles can form spheric shape network in the presence of calcium ions as templates to control the morphology of hybrid calcium carbonate. The direct proofs were obtained through TEM. Surprisingly enough, the hybrid particles have strongly acid resistant properties. After the acid resistant mechanism was successfully illuminated, the condition under which the hybrid particles can be dissolved was found.Polyelectrolyte microcapsules were fabricated by LBL technique with differentpolyelectrolyte kinds for instance PAH/PAA, PADA/PSS, and PAH/PSS on the hybrid templates. It’s observed that the hybrid capsule have good speric shape, good dispersity through Confocal laser scanning microscope (CLSM), and the capsule shell is thick and compact through Scanning electronic microscope (SEM) and atom force microscope (AFM). The results showed that the block copolymer was successfully retained in the capsules. The CLSM images showed that the hybrid capsules could entrap positively-charged water-soluble substances into capsule interior with high efficiency. Further study implied that the process of induced deposition was molecule-weight dependent process. The entrapment speed decreased with the molecule weight of entrapped substances increased. But the entrapment speed was not correlative with the total entrapped amount. It’s proved that the capsule shell was bilayer complex structure, a polyelectrolyte multilayer outside and a micelles layer inside, in which the micelles layer was the key factor to the entrapment behaviors of hybrid capsules.The study of the entrapment amount of different substances with different charged properties or/and molecule weight into the capsule interior showed that the encapsulation amount is concentration dependent, greatly increased with the increase of concentration in bulk solution, further study of the release behaviors of capsule filled with different substances suggested that the structure of capsule shell has crucial influence on the release behaviors of capsule. Furthmore, the molecule weight and the charge properties of filled substances have influence on capsule release behaviors to different extent.更多还原