Surface molecular motions of monodisperse proton-terminated polystyrene (PS-H), monocarboxyl-terminated PS (PSCOOH) and dicarboxyl-terminated PS (α,ω-PS(COOH)2) ultrathin films were investigated on the basis of lateral force microscopic (LFM) measurement at 293 K, as a function of number-average molecular weight, Mn, and chain end functionality. In the case of the PS-H thin films with Mn = 19.7 k and 40.4 k spin-coated onto Si-wafer, the surface molecular motion was activated in a glass-rubber transition state at 293 K due to the excess free volume induced by a surface localization of chain end groups. Also, in the cases of the PSCOOH (Mn = 9.7 k, 45.9 k) and the α,ω-PS(COOH)2 (Mn = 12.0 k, 51.7 k) ultrathin films spin-coated onto Si-wafer and their annealed ones at 393 K for 8 h, the surface molecular motion was also enhanced even at room temperature due to a weak ionic interaction between Si-OH of substrate and -COOH end group. On the other hand, the PSCOOH (Mn = 9.7 k, 45.9 k), and the α,ω-PS(COOH)2 (Mn = 12.0 k, 51.7 k) spin-coated ultrathin films onto aminosilane-treated Si-wafer did not show any distinct activation of surface mobility owing to a specific interaction between NH2-group of aminosilane-treated Si-wafer and -COOH end group of PS, being independent of annealing temperature, Mn and functionality.
All Science Journal Classification (ASJC) codes
- Polymers and Plastics
- Materials Chemistry