Morphology and Phase Transitions in Styrene-Butadiene-Styrene Triblock Copolymer Grafted with Polyhedral Oligomeric Silsesquioxanes

摘要

Symmetric triblock copolymer of styrene-butadiene-styrene (SBS) was grafted with varying amounts of polyhedral oligomeric silsesquioxane (POSS) with different organic moieties. The POSS, R'R_7Si_8O_(12), was designed to contain a single silane functional group, R', which was used to graft onto the dangling 1,2 butadienes in the mid-butadiene block, while the other seven identical organic group, R_7, interact with styrene end-blocks at different level. Morphology and phase transitions of these POSS-modified SBS triblock copolymers were investigated using time-resolved small angle X-ray scattering and rheological methods. It was observed for isobutyl moiety POSS (iBu-POSS), appears to show a high affinity to stay in the butadiene domain. While phenyl moiety POSS (Ph-POSS), due to its preference with styrene blocks, the driving force to reduce enthalpy comes at expense of the entropy to remain in butadiene domain, leading to a qualitative change at the interface of phase separated domains.