The molecular level investigation on surface structures of styrene/ butadiene block copolymers with different chain architecture

The effects of chain architecture and solvents on the surface structure of styrene(S)/butadiene(B) block copolymers were investigated by contact angle measurement,atomic force microscopy (AFM) and sum frequency generation vibrational spectroscopy (SFG). The results showed that PB component in SB diblock copolymer was segregated easiler on the outmost surface than that in SBS triblock copolymer. When PB selective solvent cyclohexane was used,the surface of SB was completely covered by PB component and the surface of SBS was composed of both PB and PS components. When PS selective solvent toluene was used,both SB and SBS surfaces were composed of PB and PS components with a relatively higher PS content. We believe that the resulting surface structure after solidification was controlled by the conformation of copolymer chains in their solutions.