2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

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

D.B. Drazkowski and A. Lee
Michigan State University, US

Keywords:
SAXS, block copolymers, phase transitions

Abstract:
Two symmetric triblock copolymers of polystyrene-butadiene-polystyrene (SBS) with different styrene content were grafted with varying amounts of polyhedral oligomeric silsesquioxane (POSS) molecules with either isobutyl or phenyl moiety. The POSS octamers, R’R7Si8O12 were designed to contain a single silane functional group, R’, which was used to graft onto the dangling 1,2 butadienes in the polybutadiene block and seven identical organic groups, R=isobutyl (iBu) or phenyl (Ph). Morphology and phase transitions of these POSS-modified SBS triblock copolymers were investigated using small angle X-ray scattering and rheological methods. It was observed that POSS with isobutyl moiety, when grafted to the polybutadiene (PB), appears to show a high affinity to stay within the PB domain; effectively, enhance the segregation between butadiene and styrene domains. While for PB block grafted with Ph-POSS, due to the preference of Ph-POSS for the polystyrene block. The driving force to reduce enthalpy comes at expense of the entropy for the remaining polybutadiene block, leading to a qualitative change at the polystyrene-polybutadiene interface.

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