Surface properties of thiol-terminated thermo-sensitive polymers immobilized on gold

Thiol-functionalized poly(ethoxyethyl glycidyl ether)s (PEEGEs) are synthesized by an anionic ring-opening polymerization and immobilized on gold substrates through Au-S bonding. The amount of adsorbed PEEGE is determined by QCM. The water contact angle (CA) on the PEEGE-modified gold substrate reversibly changes at a given temperature, which is close to the phase separation temperatures of PEEGE aqueous solutions. The change in CA is attributable to the coil-globule transition of PEEGE on the substrate. The temperature at which CA changes is higher for the polymer with a higher molecular weight, which is contrast to the molecular weight dependence of the phase-separation temperature in aqueous solution.