Self-Assembly of Polystyrene-b lock-Poly (Ethylene Oxide) Copolymers at the Air− Water Interface: Is Dewetting the Genesis of Surface Aggregate Formation?

摘要: Block copolymer self-assembly at the air−water interface is commonly regarded as a two-dimensional counterpart of equilibrium block copolymer self-assembly in solution and in the bulk; however, the present analysis of atomic force microscopy (AFM) and isotherm data at different spreading concentrations suggests a nonequilibrium mechanism for the formation of various polystyrene-b-poly(ethylene oxide) (PS-b-PEO) aggregates (spaghetti, dots, rings, and chainlike aggregates) at the air−water interface starting with an initial dewetting of the copolymer spreading solution from the water surface. We show that different spreading concentrations provide kinetic snapshots of various stages of self-assembly at the air−water interface as a result of different degrees of PS chain entanglements in the spreading solution. Two block copolymers are investigated:  MW = 141k (11.4 wt % PEO) and MW = 185k (18.9 wt % PEO …