Synthesis of sequence-controlled copolymers from extremely polar and apolar monomers by living radical polymerization and their phase-separated structures

A series of copolymers composed of two monomer units having a polar phosphorylcholine group and an apolar fluorocarbon group with a controlled monomer unit sequence were synthesized by a reversible addition-fragmentation chain transfer (RAFT) living radical polymerization method. 2-Methacryloyloxyethyl phosphorylcholine (MPC) and 2,2,2-trifluoroethyl methacrylate (TFEMA) were selected as the monomers, because they have disparate polarity. Furthermore, to investigate the influence of the monomer unit sequence in a polymer chain on the phase-separated structure in the bulk and surface structure, copolymers having a continuous change in the monomer unit composition along the polymer chain (gradient copolymer) were synthesized, as well as random and block copolymers. The analysis of instantaneous composition revealed a continuous change in the monomer unit composition in the gradient copolymer and the statistical monomer unit sequence in the random copolymer. Thermal analysis assumed that the gradient sequence of the monomer unit would make the phase-separated structure in the bulk ambiguous, while the well-defined and monodispersive block sequence would undergo the distinct phase-separation due to the extreme difference in the polarity of the component monomer units. The preliminary surface characterization of the synthesized polymers indicated the monomer unit sequence in the polymer chain would much influence on the surface structure. (c) 2005 Wiley Periodicals, Inc.