Effect of Chain End Group–Substrate Interaction on Surface Molecular Motion of Polystyrene Ultrathin Films

Abstract

Surface molecular motions of monodisperse proton-terminated polystyrene (PS-H), monocarboxyl-terminated PS (PSCOOH) and dicarboxyl-terminated PS (a,w-PS(COOHh) ultrathin films were investigated on the basis of lateral force microscopic (LFM) measurement at 293 K, as a function of number-average molecular weight, M •. and chain end functionality. In the case of the PS-H thin films with M. = 19.7k and 40.4k 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 (M.=9.7k, 45.9k) and the a,w-PS(COOHh (M.= 12.0k, 51.7k) 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 (M.=9.7k, 45.9k), and the a,w-PS(COOH)2 (M.= 12.0k, 51.7k) spin-coated ultrathin films onto aminosilane-treated Si-wafer did not show any distinct activation of surface mobility owing to a specific interaction between NH 2-group of aminosilane-treated Si-wafer and-COOH end group of PS, being independent of annealing temperature, M. and functionality. KEY WORDS Proton-Terminated Polystyrene I Monocarboxyl-Terminated Polystyrene I Dicarboxyl-Terminated Polystyrene I Lateral Force Microscopy I Surface Molecular Motion I Aminosilane-Treated Si-Wafer I

A Study of Morphology and Intercalation Kinetics of Polystyrene−Organoclay Nanocomposites

“…They also reported that monodisperse polystyrene with molecular weight less than 30 000 is at the glass−rubber transition even at 293 K; , the T g depression of polydisperse polystyrene is greater than the monodisperse samples due to the chemistry of the chain ends: 35 the surface has chain end segregation as determined by secondary ion mass spectroscopy depth profiling, and polystyrene end-capped with a fluorinated group reduced T g more than the proton end-capped polymer . Thin, monodisperse polystyrenes terminated by proton and carboxylic acid group on a silane-treated silicon substrate show reduction of the degree of T g suppression seen in the free-standing films by a strong film−substrate interaction …”

“…32 In a related subject of thin film T g , an extensive investigation has been carried out on the surface T g by the group of Kajiyama and Takahara in the past several years. [33][34][35][36][37][38] Conclusions common to these papers are that the T g of the polymer surface is lower than the bulk, which is attributed to the segregation of the chain ends near the surface. Expectedly, this conclusion is the same as that obtained from free-standing thin films already described previously.…”

“…38 Thin, monodisperse polystyrenes terminated by proton and carboxylic acid group on a silane-treated silicon substrate show reduction of the degree of T g suppression seen in the freestanding films by a strong film-substrate interaction. 37 T g depression of ultrathin films was explained by de Genne using the two competing motions: (i) standard motions which are controlled by the free volume and (ii) collective motions along the chain, which require a weaker free volume except for the end groups. 39 Many structural and conformational features of confined polymer chain behavior have been predicted by the Monte Carlo lattice and off-lattice computer simulations.…”

Striking AcOH Acceleration in Direct Intramolecular Allylic Amination Reactions

“…The author9–10 has investigated the surface morphology of carboxyl‐terminated polystyrene, PS‐COOH, on different substrates and concluded that the dewetting behavior of PS‐COOH on Si‐wafer substrate occurred upon annealing. Also, the adsorption of modified polymer onto solids from solution is not only of academic interest but is also a fundamental aspect of numerous applications such as electronic devices, coating, and lubrication.…”

Dewetting of Thin Film Blends Containing Block Copolymer: Effects of Nonadsorbing Block Length and Substrate Hydrophobicity

“…One surface investigated here, and in prior studies, ,, is SiO x , which is a hydrophilic surface. To create a more hydrophobic yet polar surface, a self-assembled monolayer (SAM) terminated with an amino group − is deposited on SiO x . Our studies will show that a stronger matrix−substrate interaction is partly responsible for improved film stability on amine-terminated surfaces.…”