Preparation And Release Properties Of Polyaniline And DTT-TMPTA Microspheres

Functional polymer microspheres, which were defined as microspheric polymers with particle size from nanometer to micrometer, have many excellent features, such as large specific surface area, modified surface and unique optical/electrical properties. Recently, the applications of functional polymer microspheres in self-healing anticorrosion coatings and biomedical areas have been quickly developed. In this article, PANI microspheres with controlled particle size were prepared by microemulsion polymerization for the application of self-healing anticorrosion coatings; while functional hydrogel microspheres were synthesized by non-aqueous emulsion. The release properties of the synthesized microspheres were also investigated for the application of controlled drug release.In this article, polyaniline(PANI) microspheres were synthesized by microemulsion polymerization. The affect of emulsifier kinds and concentration, co-emulsifier kinds and content as well as the molar ratio of monomers to the morphology of microspheres were investigated. FT-1R、UV-vis、SEM、TEM、XRD and TG-DSC were applied to characterize the structure, properties and morphology of microspheres. The results revealed that polymer microspheres with a diameter range from 100 to 1000 nm were obtained when SDS and PVA was used as emulsifier and co-emulsifier, APS as oxidant (the molar ratio of APS to aniline was 1:1), respectively. The increase of PVA-1799 content facilitated the formation and stability of microemulsion, while the diameter of microspheres decreased with the increased SDS concentration. Moreover, poly(2,5-dimethoxy aniline-co-aniline) copolymer microspheres with a particle size of 1 μm were obtained by microemulsion polymerization when the molar ratio of 2,5-dimethoxy aniline to aniline was 1:5. The addition of 2,5-dimethoxy aniline increased the stability of microemulsion and facilited the formation of microspheres, while the thermal stability declined and excess 2,5-dimethoxy aniline would result in the crack of microspheres. Thus, the desirable molar ratio of [2,5-dimethoxy aniline]:[aniline] was decided to be 1:5～1:9. In addition, the release of self-healing agent from PANI microspheres was investigated and the result indicated that it was controlled by diffusion.Besides, no-aqueous emulsion polymerization was applied to prepare DTT-TMPTA hydrogel microspheres with PS-PB-PS as emulsifier, polar organic solvent (acetonitrile) and nonpolar organic solvent (cyclehexane) as dispersed and continuous phase, respectively. Different feeding methods, emulsifier concentration and monomer molar ratio were applied to prepare hydrogel microspheres with different morphology and diameters. The structure and morphology were characterized by FT-IR, SEM and UV-vis. The release of CPT by microspheres in different pH buffers was also investigated. The optimum condition for the preparation monodispersed microspheres was defined as:feeding method-2, the concentration of PS-PB-PS was 19.48 g/L, the volume ratio of acetonitrile to cyclehexane was 1:30, the molar ratio of DTT and TMPTA was 3:2. The diameter of microspheres decreased from 4.08 μm to 680 nm with the emulsifier content increased from 3.22 g/L to 32.45 g/L. In addition, the swelling ability rised with the increase of DTT content. The release ratio of CPT by hydrogel microspheres was faster in pH=7.4 buffer and it was swelling-controlled when Mt/M∞≤0.6 and diffusion-controlled when Mt/M∞≤0.6.