ADXPS/STEM STUDIES OF SURFACE AND BULK MICROPHASE BEHAVIOR IN BLOCK-COPOLYMERS AND GRAFT-COPOLYMERS AND THEIR BLENDS

This study of surface and bulk microphase separation compares different block chemistries and topologies. The molecular weight and percentage of the siloxane block dominated the phase behavior, which showed coincident transitions at surfaces and in the bulk. Conditions were found where periodic arrays of spheres, lamellae or cylinders formed in the bulk, and spheres were observed at some of the surfaces. Thus quantitative interpretation of ADXPS depth profiles is questionable. Blends of copolymers with homopolymer show pronounced surface segregation with a critical concentration at ≈1 wt% siloxane in the bulk that saturates the surface. The extent of surface and bulk phase separation is strongly effected by the kinetics of solvent evaporation or thermoforming. © 1990.