Micellization and high internal phase emulsion stabilization of Poly(y-phenyl-e-caprolactone)-b-methoxy Poly(ethylene glycol) block copolymers synthesized via cationic ring opening polymerization

초록

Amphiphilic diblock copolymers of poly(y-phenyl-e-caprolactone)-block-methoxy poly(ethylene glycol) (PPhCLxb-mPEG, where x represents the PhCL mol% in the copolymer) were synthesized via cationic ring-opening polymerization (CROP) and proceeded through an activated monomer mechanism (AMM), with variation of the hydrophobic block length. The introduction of phenyl substituents retarded the polymerization rate and disrupted chain packing, leading to reduced crystallinity compared to analogous poly(e-caprolactone)-blockmPEG (PCLn-b-mPEG where n represents the PCL mol% in the copolymer) at comparable molecular weight. The micellization behavior of PPhCLx-b-mPEGs was investigated to evaluate their emulsification capability. Despite greater hydrophobicity, as evidenced by higher water contact angles, PPhCLx-b-mPEG exhibited a significantly higher critical micelle concentration (CMC), which is attributed to steric hindrance during micelle core formation. Emulsion stability measurements revealed that high internal phase emulsions (HIPEs) stabilized by PPhCLxb-mPEGs exhibited significantly improved stability compared with those stabilized by PCL67-b-mPEG. PPhCLx-bmPEGs were successfully employed as emulsifiers for HIPE polymerization, resulting in the formation of highly porous polyHIPE materials. The observed decrease in pore size with increasing PPhCL chain length demonstrated the improved structure-directing capability of PPhCLx-b-mPEG in the formation of polyHIPE foams. Compared to conventional small-molecule surfactants, this approach enables precise control over pore morphology through systematic variation of block length during synthesis, representing a versatile strategy for tailoring polyHIPE structures.

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