Novel amphiphilic temperature responsive graft copolymers PCL-g-P(MEO2MA-co-OEGMA) via a combination of ROP and ATRP: synthesis, characterization, and sol-gel transition

Abstract

A series of well-defined novel amphiphilic temperature-responsive graft copolymers containing PCL analogues P(αCleCL-co-eCL) as the hydrophobic backbone, and the hydrophilic side-chain PEG analogues P(MEO2MA-co-OEGMA), designated as P(αCleCL-co-eCL)-g-P(MEO2MA-co-OEGMA) have been prepared via a combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The composition and structure of these copolymers were characterized by 1H NMR and GPC analyses. The self-assembly behaviors of these amphiphilic graft copolymers were investigated by UV transmittance, a fluorescence probe method, dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. The results showed that the graft copolymers exhibited the good solubility in water, and was given the low critical temperature (LCST) at 35(±1) °C, which closed to human physiological temperature. The critical micelle concentrations (CMC) of P(αCleCL-co-eCL)-g-P(MEO2MA-co-OEGMA) in aqueous solution were investigated to be 2.0 × 10−3, 9.1 × 10−4 and 1.5 × 10−3 mg·mL−1, respectively. The copolymer could self-assemble into sphere-like aggregates in aqueous solution with diverse sizes when changing the environmental temperature. The vial inversion test demonstrated that the graft copolymers could trigger the sol-gel transition which also depended on the temperature.