Segregation of SEBS Triblock Copolymers to the Interface between Immiscible Homopolymers

Abstract

Segregation of poly(styrene-b-[ethylene-butylene]-b-styrene) (SEBS) triblock copolymer to the interface between immiscible homopolymers was investigated. The homopolymers used were polystyrene (PS) and low density polyethylene (LDPE). Polymer-polymer interfaces samples were prepared by spin coating thin polymer films from solution onto silicon substrates. The contrast between layers of polymer films investigated using the neutron reflectivity (NR) technique was enhanced by means of isotopic substitution. The segregation behavior of the SEBS triblock copolymer was investigated using bilayer and trilayer sample arrangements. Interpretation of the reflectivity of the samples was carried out by comparing the scattering length density profile which provides a best fit to reflectivity data, to the one estimated at 150oC for the polymers used. The interpretation of these NR results indicated that the SEBS triblock copolymers segregated to the interface between PS and LDPE, where the blocks of the copolymer penetrate into the respective homopolymer phases. Miscibility between the blocks of the copolymer and the respective homopolymer layers was also observed.