Controlled synthesis of cellulose-graft-poly[2-(diethylamino)-ethyl methacrylate] by ATRP in ionic liquid [AMIM]Cl and its pH-responsive property

The pH-responsive cellulose-g-poly[2-(diethylamino)-ethyl methacrylate] (cellulose-g-PDEAEMA) copolymers were successfully synthesized by atom transfer radical polymerization (ATRP) in the ionic liquid 1-allyl-3-methylimidazolium chloride ([AMIM]Cl). As the functional monomer 2-(diethylamino)ethyl methacrylate (DEAEMA) hardly dissolved in [AMIM]Cl, we used ethyl alcohol as the cosolvent to increase its solubility and thereby form a homogeneous system. Compared with the synthetic mechanism for the heterogeneous system, generation of the byproduct poly[2-(diethylamino)ethyl methacrylate] (PDEAEMA) in the homogeneous system was reduced and the ATRP reaction was easily controlled. Optimum reaction condition was attained at the CuBr/PMDETA/DEAEMA/ethyl alcohol molar ratio of 1:15:150:300. Kinetic analysis confirmed the reaction was living and controllable. Cellulose-g-PDEAEMA was characterized through FTIR, 1 H NMR, TEM and GPC. The results showed that the PDEAEMA brush was covalently bonded to the cellulose backbone and its molecular weight distribution was narrow. In addition, the resultant copolymer could self-assemble into spherical micelles and showed the pH-sensitivity, implying its potential application as biomedical materials.