Synthesis and micellization of P(NIPAM-co-HMAM)-b-PEO-b-P (NIPAM-co-HMAM) triblock copolymers

Temperature-responsive P(NIPAM-co-HMAM)-b-PEO-b-P(NIPAM-co-HMAM) triblock copolymers were synthesized by an atomic transfer radical polymerization (ATRP) method without freeze-pump-thaw cycles. The composition, structure, and molecular weight of the synthesized block copolymer were characterized by H-1 NMR and GPC. The phase transitions induced by temperature for different copolymers in dilute aqueous solutions have been studied using transmittance measurements, laser particle size measurements, viscosity analysis, and surface tension measurement, which showed that the HMAM content and the PEO (or PEG) chain length in the synthesized triblock copolymer affects the copolymer's lower critical solution temperature (LCST). The micellization behavior of each temperature-responsive triblock copolymer was investigated by fluorescence probe measurements and transmission electron microscopy (TEM), which showed that the triblock copolymers form stable micelles above the LCST. The introduction of the HMAM component and the formation of micelles represent the first steps in the development of an injectable gel that forms in situ through chemical and physical crosslinking.