Study Of Novel "Micelles-Enhanced" Polyelectrolyte Microcapsules Based On Functional Templates

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.