Synthesis of ethyl cellulose-based thermal- and photo- dual-responsive copolymer via ATRP and their aggregates in aqueous solution

摘要

Ethyl cellulose-grall-poly(N-isopropylacrylanmle-ro-6-[4-(4-etlK)xyphenylazo)phenoxy] hexyl methacrylate) (EC-g-P(NIPAM-ro-MAZO)) were synthesized through atom transfer radical polymerization (ATRP). Ethyl cellulose-based macroiniliator was prepared by direct acrylation of ethyl cellulose with excess 2-bromoisobulyryl bromide at room temperature, the bromo-ester groups of which were known to be efficient initiator for ATRP. Statistical copolymerizalion of N-isopropylacrylamide (NIPAM) and 6-|4-(4-ethoxyphenylazo)phenoxy] hcxyl methacrylate (MAZO) onto ethyl cellulose (EC) was achieved using CuCl/Mc_6,TREN as the catalyst system and N,N-dimethylformamide/water mixture (DMF/H_2O). v/v 4:1) as solvent. Appropriate solvent concentration and polymerization temperature can minimize the mtermolecular coupling and render the polymerization controllable. The aggregates formed by EC-g-P (NIPAM-ro-MAZO) copolymer in aqueous solution were investigated by varying temperature and irradiation under UV/visible light. The results indicated that the copolymer had thermal- and photo- dual-responsive properties. The copolymer formed a comparatively stable suspension in water at room temperature and underwent a hydrophilic-hydrophobic transition when the temperature raised, furthermore, their aggregates in water were influenced by isomerizalion of azobenzene groups under UV visible light irradiation.