Design of Oligo(ethylene glycol)-based thermoresponsive polymers: An optimization study

Co-polymers of 2-(2-methoxyethoxy)ethyl methacrylate (MEO(2)MA) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA(300), M-n = 300 g/mol) of various composition were synthesized at 60 degrees C in ethanol solution either by conventional radical polymerization (RP) or atom transfer radical polymerization (ATRP). Both techniques led to co-polymers P(MEO(2)MA-co-OEGMA(300)) in high yields. However, ATRP provided better defined co-polymers with controlled molecular weight, composition and molecular weight distribution. Nevertheless, all the samples exhibited a lower critical solution temperature (LCST) in aqueous medium (i.e., pure deionized water or physiological buffer). Sharp and reversible phase transitions were observed in all cases by turbidimetry and dynamic light scattering. This thermoresponsive behavior was demonstrated to be directly linked to the MEO(2)MA/OEGMA(300) composition of the formed co-polymers. Thus, the LCST of the co-polymers could be precisely adjusted in the temperature range 28-65 degrees C.