POLYELECTROLYTE MICROCAPSULES FABRICATED VIA in situ COACERVATION - THE INFLUENCE OF DOPED POLYELECTROLYTE AMOUNT IN THE TEMPLATES ON THEIR STRUCTURES AND PROPERTIES

The fabricating conditions for the in situ coacervated polyelectrolyte microcapsules were optimized, and their influences on the capsule structures and properties were elucidated. Poly(styrene sulfonate) (PSS) doped CaCO3 was first used as an additive to modify the growth of CaCO3 microparticles. During this process, the PSS molecules were integrated into the CaCO3 particles or adsorbed on their surfaces. By changing the feeding concentration of the PSS during the fabrication, the PSS doped CaCO3 particles with a PSS content of 4% similar to 11% were obtained. After only one layer of poly(allylamine hydrochloride) (PAH) was adsorbed onto the PSS-doped CaCO3 particles, the templates were dissolved by disodium ethylene diamine tetraacetate dihydrate (EDTA) to liberate the PSS molecules, which in situ coacervated with the coated PAH to form the capsule walls. After complete removal of the templates, intact complex microcapsules were successfully obtained. Results showed that all the CaCO3 particles with different PSS amount could be used as the templates to fabricate the coacervated microcapsules. The structures of the as-prepared microcapsules were characterized by confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM) and scanning force microscopy (SFM) finding no significant influence of the PSS doped amount in the CaCO3 particles. Compared with layer-by-layer (LbL) assembled polyelectrolyte microcapsules, the complex microcapsules shrank more seriously in 5 mol/L NaCl solution because their walls have net negative charge which is more sensitively screened by the salt. Due to the repulsion of the negative charge in the capsule walls, the complex microcapsules showed better ability against the thermal induced shrinkage. Because of the less ordered structures compared with the LbL microcapsules, the coacervated walls of the complex microcapsules possessed higher cut-off molecular weight. Therefore, one can conclude that the amount of the doped PSS in the CaCO3 particles has no significant influence on the structures and properties of the coacervated microcapsules, and thus the method is more attractive in terms of quality control. Moreover, the method can be extended to other polyelectrolyte systems as well, for example, natural biomacromolecules.