Surface and Bulk Microphase Separation in Siloxane-Containing Block Copolymers and Their Blends: The Roles of Composition and Kinetics.

摘要

Using the combination of angular-dependent x-ray photo-electron spectroscopy (XPS or ESCA) and transmission electron microscopy (TEM), the effects of physical and chemical composition, block size, processing conditions and kinetics on microphase separation in the bulk and on surface segregation wer elucidated in four families of block copolymers and their blends with homopolymers. Siloxanes of varying block size and chemistry in perfectly alternating copolymers with bis-A sulfone, aromatic ester, urea and imide provided a basis for generalizations about the relationships between surface and bulk microphase separation, as well as the effect of block sizes upon the thickness and compositional gradients in the overlayers. There was a rapid increase in surface siloxane concentration of blends at 1-10% in the bulk, corresponding to the appearance of macrophase separation of block copolymer from the homopolymer matrix. Above 25-35% the copolymer became the continuous phase and the surface composition of blends became essentially the same as that of pure copolymer. (JES)