Surface molecular mobility for copolymers having both hydrophobic and hydrophilic side chains via dynamic contact angle measurement

The reorganization of a surface structure in response to a change in environmental media was investigated for copolymers having both hydrophobic polydimethylsiloxane (PDMS) and hydrophilic methoxypoly-ethyleneglycol (MPEG) side chains via dynamic contact angle (DCA). These copolymers showed a large contact angle hysteresis and a dependency of the advancing and receding contact angle on dipping velocity (DV). Composition dependency of DCA for these copolymers is also discussed. In addition to this, adhesion tension relaxation, F(t), for MMA/MPEGMA/PDMSMA was determined. F(t) in the advancing process increased with elapsed time and decreased in the receding process. These phenomena were explained by the adsorption and reorientation of hydrophilic segments to the water/copolymer interface in water. In XPS analysis, more oxygen atoms were detected on the surfaces of MMA/MPEGMA after immersion in water than before. For MMA/MPEGMA/PDMSMA, the atomic ratio of Si to C increased with an increase in PDMSMA content.