Synthesis Of Thermo-Responsive Polymer Materials Via ATRP Under Mild Conditions

In this paper, a series of poly(N, N-dimethylaminoethyl methacrylate) (PDMAEMA) homopolymer with different degree of polymerization were synthesized by atom transfer radical polymerization (ATRP) in aqueous media firstly. And this polymerization reaction used 2-bromoisobutyrate (EBIB) as initiator, CuBr as catalyst, PMDETA as ligand, 2-dimethylaminoethyl methacrylate (DMAEMA) as monomer. The macroinitiator PEG-Br was first prepared from methoxypolyethylene glycols (PEG) and 2-bromoisobutyryl bromide (BIBB). Then a series of PEG-b-PDMAEMA copolymers with different lengths of PDMAEMA segments were synthesized by ATRP in aqueous media using PEG-Br as macroinitiator, DMAEMA as monomer, CuBr as catalyst, PMDETA as ligand. GPC, FT-IR and 1H-NMR measurements indicated that the homopolymers and copolymers were both well controlled. UV-Vis results showed that PDMAEMA homopolymers and PEG-b-PDMAEMA copolymers both exhibited thermosensitivity.The kinetic data come from 1H-NMR showed that the polymerization process of PDMEAMA and PEG-b-PDMAEMA were both in accordance with the first-order kinetic characteristics which indicated that the reaction system with good controllability. UV-Vis results indicated that the low critical solution temperature (LCST) became lower when increasing the concentration of·polymer solution. Moreover, the longer the DMAEMA chain segments, the lower the LCST of PDMAEMA and PEG-b-PDMAEMA was. Compared to PEG-b-PDMAEMA copolymer, the LCST of PDMAEMA homopolymer with the same length of DMAEMA segment was low since the absence of PEG hydrophilic segment. By adjusting fore-mentioned factors we found that the 1.0%wt of PEG-b-PDMAEMA3oo aqueous solution with a LCST close to body temperature, which can be a potential carrier of drug.The ATRP was carried out in aqueous media at 30 ℃, the react condition is very mild. Thus it’s expected to be applied in the biomedical field. PEG-b-PDMAEMA copolymer is not only hydrophilic, but also has significant thermosensitivity with a LCST ranging from 35 ℃～42 ℃ which is close to body temperature, making them promising in biomedical applications.