Thermosensitive copolymers with lower critical solution temperature (LCST) were prepared by copolymerization of N

N-dimethylacrylamide and diacetone acrylamide through conventional free radical polymerization in water using K2S2O8-Na2SO3 redox system as an initiator.The thermal responsiveness as well as temperature dependent structure of the copolymer solution was systematically examined through ultraviolet-visible spectroscopy(UV-Vis)

dynamic light scattering (DLS)

fluorescence spectrophotometer and 1H-NMR.All these results demonstrate that P(DMA-co-DAAM)s exhibit a significant thermal-induced association behavior.At lower temperatures P(DMA-co-DAAM) was disolved in the form of unimers while these unimers would transform to micellar aggregates due to the association of hydrophobic segments along the chains at higher temperatures.Such phenomenon was ascribed to the changes in hydrophilic-hydrophobic balance of DAAM pendant groups with increasing in temperature.Further research also implies that the association transition temperature of the copolymer solutions could be effectively regulated by changing the composition and concentration of the copolymers.Lower association transition temperatures could be obtained at higher contents of DAAM

which held a well linear relationship in our experiments.It demonstrates that the inter-chain heterogeneity and polydispersity originating from common radical polymerization exhibit little influence on the thermal sensitive behaviors of P(DMA-co-DAAM).