Self-organization of graft copolymers at surfaces, interfaces and in bulk

摘要

The morphology in bulk and thin film of high-integrity graft copolymers has been investigated by small angle neutron and light scattering, neutron reflectivity, and transmission electron microscopy. The model graft copolymers are based on two chemically incompatible-blocks composed of an elastomeric polyethylacrylate backbone onto which pendant monodisperse thermoplastic polystyrene are statistically placed. Two different levels of graft corresponding to an average of 1 and 3 per chain were investigated. In the bulk phase, the low graft level shows irregular fractal-like structures while the high graft level exhibits lamellar microdomains. In thin film, ordered structures were observed also in both compositions. The interphase adhesion between the polystyrene and the polyethylacrylate microdomain was investigated by uniaxially elongating the copolymer films. The low level graft material exhibits normal behavior characteristic of filler-reinforced rubber: the isotropic scattering pattern deforms in an anisotropic manner, i.e., ellipsoid-shaped with the long axis perpendicular to the stretching direction. An ''abnormal Butterfly'' pattern was observed with the high graft level. The butterfly pattern is attributed to the deformation of the lamellar morphology of the copolymer.