Microscopy and laser diffraction investigation of block copolymers used as adhesives

In a previous paper, we established a relationship between the adhesive properties and the chain characteristics of ABA poly(styrene-b-isoprene) block copolymers (or SIS). Only copolymers which do not easily undergo phase separation give joints with high tensile lap-shear resistance. By optical and electron microscopy, as well as by laser diffraction, we have now studied the structure of a series of SIS copolymers. We found that a random distribution of small polyisoprene noduli in the polystyrene matrix effectively exists in SIS which show good adhesive properties.