Hydrogen bonding strength effect on self-assembly supramolecular structures of diblock copolymer/homopolymer blends

In this study we investigated the steric hindrance effect on the hydrogen bonding strength and self-assembly supramolecular structures of the poly(styrene-b-vinylphenol) (PS-b-PVPh) diblock copolymer when blended with the homopolymers poly(4-vinylpyridine) (P4VP) and poly(2-vinylpyridine) (P2VP). Each of these PS-b-PVPh/P4VP and PS-b-PVPh/P2VP blends underwent a sequence of order–order morphological transitions with wet-brush behavior from lamellae to hexagonally packed cylindrical to spherical structures. Interestingly, we observed a bicontinuous gyroid structure only in the more strongly hydrogen bonding PS-b-PVPh/P4VP blend. Furthermore, the PS-b-PVPh/P4VP blend exhibited its order–order morphological transitions at relatively low homopolymer concentrations and did not display a two-phase region at relatively high homopolymer concentrations. Thus, differences in the steric bulk of the homopolymers P4VP and P2VP affected their hydrogen bonding with the diblock copolymer PS-b-PVPh and, therefore, influenced the self-assembled structures formed from their blends.