Synthesis of end-functionalized poly(N-isopropylacrylamide) with group of asymmetrical phthalocyanine via atom transfer radical polymerization and its photocatalytic oxidation of Rhodamine B

A novel asymmetrical zinc(II) phthalocyanine (ZnPcBr) was synthesized as the initiator for atom transfer radical polymerization (ATRP). Using CuBr/tris(2-dimethylaminoethyl) amine (Me6TREN) as the catalyst system, the ATRP of N-isopropylacrylamide (NIPAM) was carried out to afford a new linear poly(N-isopropylacrylamide) with end group of asymmetrical phthalocyanine (ZnPc-PAM). The structures of the initiator and the polymers were characterized by means of FT-IR and H-1 NMR. Polydispersity index (PDI) obtained by gel permeation chromatography (GPC) indicated that the molecular weight distribution was narrow. The lower critical solution temperatures (LCST) for the aqueous solutions of ZnPc-PAM, measured by turbidimetry method and differential scanning calorimetry (DSC), respectively, were increased due to the incorporation of the phthalocyanine group at the chain end and lowered with increasing molecular weight. It was verified that ZnPc-PAM possessed photocatalytic activity by the degradation of Rhodamine B in the presence of hydrogen peroxide under visible light. Moreover, it presented the highest catalytic efficiency at around its LCST owing to the thermo-sensitive property, which benefited the recycling of the polymeric photocatalyst.