Phase Behavior of Binary Mixtures of Block Copolymers having Hydrogen Bonding

The phase behavior of binary mixtures of high molecular weight polystyrene-\textit{block}-poly(2-vinyl pyridine) (PS-$b$-P2VP) and low molecular weight polystyrene-\textit{block}-poly(4-hydroxystyrene) (PS-$b$-PHS) copolymers was investigated by using small angle X-ray scattering and transmission electron microscopy. Both block copolymers exhibited lamellar microdomains. When the weight fraction of PS-$b$-PHS in the blend was less than 0.1, lamellar microdomains are maintained. However, with increasing amount of PS-$b$-PHS, the microdomains are transformed to hexagonally-packed cylindrical microdomains, and body-centered cubic spherical microdomains. This is attributed to the hydrogen bonding between P2VP and PHS blocks.