Dynamic motion of phosphorylcholine groups at the surface of poly(2-methacryloyloxyethyl...

A series of novel random copolymers composed of hydrophilic and hydrophobic monomer units have been synthesized by a conventional radical polymerization method. As the hydrophilic monomer unit, 2-methacryloyloxyethyl phosphorylcholine (MPC) was selected because the MPC polymers are well known for their excellent bio- and blood compatibilities. The semifluorinated monomer, 2,2,2-trifluoroethyl methacrylate (TFEMA), was used as the hydrophobic monomer. The surface analysis of the copolymer by X-ray photoelectron spectroscopy, dynamic contact angle measurement, and zeta-potential measurement showed that the TFEMA unit was concentrated at the outermost surface in the dry state. The dynamic reorientation of the MPC unit occurred in the wet state because the MPC unit had a strong hydrophilic character. As a result, the monomer unit composition on the surface became almost the same as that in the bulk. Nevertheless, the properties of the surface were hydrophilic in spite of the MPC unit composition of the bulk. In particular, the amount of protein adsorbed on the surface was dramatically reduced when the MPC unit mole fraction was 0.2.