Temperature response of thermoresponsive polyethers immobilized on gold substrates

Thermosensitive polymers that possess Lower Critical Solution Temperature (LCST) undergo a thermally induced reversible hydration-dehydration phase transition in aqueous solution. It has been known that the transition of polymer chain from coil to globule takes place in a narrow range of temperature. In this study, thermosensitive polyethers having thiol terminus was adsorbed onto a gold substrate through Au-S bonding. Water wetting properties of the polymer-adsorbed gold surface were observed by contact angle measurements with raising temperature, and a sharp increase in wettability occurred at 36°C. This result implies a collapse of the polymer chain on the substrate while increasing the surface temperature, turning out the surface to be more hydrophobic. Moreover, the temperature where the change in surface wettability was observed (T_w) increased with increasing the molecular weigh of polymer, suggesting that the effect of hydrophobic phenothiazine group on the polymer phase transition weakened as the molecular length had increased.