ENHANCED SEGREGATION OF A DIBLOCK COPOLYMER CAUSED BY HYDROGEN-BONDING

Utilizing forward recoil spectrometry (FRES), we have determined the segregation isotherm which describes the interfacial excess z(i)* of diblock copolymers of poly(d(8)-styrene-b-2-vinylpyridine) [dPS-PVP] at the interface between the PS/PVP, PS/poly(4-vinyl phenol) [PS/PVPh], and PS/poly(4-vinylbenzoic acid) [PS/PVBA] as a function of phi infinity, the volume fraction of diblock copolymer remaining in the host PS phase after annealing the specimens to reach the equilibrium segregation. A remarkable increase in the saturation z(i)* is observed at the PS/PVBA and the PS/PVPh interfaces as compared to that at the corresponding PS/PVP interface. This enhanced segregation is caused by an attraction due to the formation of hydrogen bonds of the PVP block with PVBA and PVPh homopolymers. The segment density profile of copolymer at the PS/PVBA interface determined by neutron reflectometry indicates that the interface is almost totally occupied by the copolymer and the copolymer chains at the interface are highly stretched. This result suggests that the interface is close to the ''brush'' structure as pictured by Leibler.