Synthesis and Application of Core-shell Structured Particles.

摘要

Engineering of particles has attracted a lot of interest because the application of particles greatly depends on their composition, structure and surface chemistry. One of the most popular strategies is fabrication of core-shell structured particles. In this thesis two types of core-shell particles were synthesized and applied in shallow trench isolation (STI) chemical mechanical planarization (CMP) and direct thermal paper for printing. In STI CMP application commonly used ceria particles were replaced by polymer core-ceria shell particles to achieve tailored properties. Different polymeric core particles e.g. poly(styrene-methyl methacrylate) were synthesized by emulsion polymerization and coated with a layer of ceria particles by self-assembly method. The mechanism of synthesizing polymer core-ceria shell particles was proposed and the CMP results showed the correlation between the composition of particles and the CMP removal rate and surface quality. In direct thermal paper application core-shell polymeric particles were synthesized using multi-stage emulsion polymerization. Different polymeric core particles e.g. poly(methyl methacrylate-methyl methacrylic acid) were synthesized and coated with a variety of polymeric shell materials such as polystyrene by seeded emulsion polymerization. The mechanism of synthesizing polymeric core-shell particles was proposed and the eect of parameters e.g. feeding rate of emulsion and temperature on the morphology of the resultant particles was discussed. The synthesized core-shell particles were treated (with ammonium hydroxide to form water-filled encapsules), formulated, and coated onto substrates to form an opaque film (thermal paper). The size, morphology, composition of the core-shell particles were optimized and the fabricated film showed an excellent whiteness and thermal sensitivity resulting in a promising commercializable product.