Thermo-sensitive zwitterionic block copolymers via ATRP

Novel thermo-sensitive zwitterionic ABC-type triblock copolymers poly(ethylene glycol)-block-[2-(methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)-ammonium hydroxide-block-poly[2-(dimethylamino)ethyl methacrylate] (MPEG-b-PSBMA-b-PDMAEMA) were synthesized by atom transfer radical polymerization (ATRP). The bromide-terminated diblock copolymers poly(ethylene oxide)-block-[2-(methacryloyloxy) ethyl]dimethyl(3-sulfopropyl)-ammonium hydroxide (MPEG-b-PSBMA-Br) were prepared by the ATRP of methacryloxyethyl sulfobetaine initiated by the macroinitiator MPEG-Br, which was obtained by the esterification of poly(ethylene glycol) monomethyl ether (MPEG) with 2-bromoisobutyryl bromide. Then, poly(2-(diethylamino) ethyl methacrylate) (PDMAEMA) was introduced by a sequential ATRP process to obtain the triblock copolymers. These copolymers with varied compositions, molecular weights and polydispersities were characterized by H-1 NMR and GPC. Variable temperature ultraviolet analysis was employed to test their stimuli-sensitive properties. These block copolymers exhibited distinct thermo-sensitivity under different molecular compositions or solution conditions. The resistance to the non-specific protein adsorption of the triblock copolymers was evaluated, and excellent antifouling property occurred. This can be attributed to surface hydration via hydrogen bonds between PEG and water molecules and the surface hydration via ionic-induction between PSBMA and water molecules. The synergistic effect resulted in an effective reduction of protein adsorption. These copolymers have potential applications as antifouling and antibacterial agents.