Surface Behavior of Amphiphilic Heteroarm Star-Block Copolymers with Asymmetric Architecture

摘要

We study the surface behavior of the asymmetric amphiphilic heteroarm poly(ethylene oxide)(PEO)/ polystyrene(PS)star polymer on solid substrate.These star polymers differ in both architecture(four-and three-arm molecules,PEO-b-PS_3 and PEO-b-PS_2)and in the length of PS chains(molecular weight from about 10 000 up to 24 000).We observed that,for a given chemical composition with a predominant content of hydrophobic blocks,the compression behavior of the PS domain structure controls the surface behavior and the final morphology of the monolayers.New features of the surface behavior of star-block copolymers are high stretching of the PS arms from the interface and enhanced stability of the circular PS domain structure,even at high compression.We suggest that for asymmetric star-block copolymers both architecture and chemical composition heavily favor the formation of highly curved interfaces and,thus,more stable circular domain structure with stretched PS arms.