Investigation of the surface rearrangement of poly(imide-siloxane) using dynamic contact angle measurements

Dynamic contact angle measurements and X-ray photoelectron spectroscopy (XP S) were used to investigate the surface compositions and surface rearrangem ent of poly(imide-siloxane) with various molecular weights and contents of amine-terminated poly(dimethyl siloxane) (ATPDMS). Four different water con tact angles were measured to study the poly(imide-siloxane) surface: the in itial advancing angle, the equilibrium advancing angle, the initial recedin g angle, and the equilibrium receding angle. Poly(imide-siloxane) with 2350 and 4300 g/mol of ATPDMS showed higher initial and equilibrium advancing c ontact angles than those of poly(imide-siloxane) with 433 g/mol of ATPDMS. Since the mobility of ATPDMS segments depended on the chain length of ATPDM S, the molecular weight of ATPDMS determined the surface composition of pol y(imide-siloxane), the rate of surface rearrangement, and the contact angle hysteresis. Poly(imide-siloxane)s with 2850 and 4300 g/mol of ATPDMS were mostly covered with ATPDMS even if just 1 wt% of ATPDMS was incorporated, w hile poly(imide-siloxane) with 433 g/mol of ATPDMS was mostly covered with polyimide segments and partially with ATPDMS. The rate of surface rearrange ment and the contact angle hysteresis decreased with the increasing molecul ar weight as well as content of ATPDMS. The actual ATPDMS-enriched layer th ickness was also investigated by XPS. The actual thickness of the ATPDMS-en riched layer was about 15 nm for 2850 g/mol and 4300 g/mol of ATPDMS-modifi ed poly(imide-siloxane) and about 7.5 nm for 433 g/mol of ATPDMS-modified p oly(imide-siloxane).