Poly(N-isopropylacrylamide-co-N

N-dimethylacrylamide) (poly(NIPAAm-co-DMAAm))

poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (poly(NIPAAm-co-HEMA)) and poly(NIPAAm-co-DMAAm-co-HEMA)) were synthesized by free radical solution copolymerization using thioglycol as chain transfer agent.Their compositions

molecular weights and thermal transitions were determined by 1H-NMR

GPC analysis and lower critical solution temperature (LCST) determination.Poly(NIPAAm-co-DMAAm) showed markedly increase in LCST with incorporation of hydrophilic DMAAm

while the LCST of poly(NIPAAm-co-HEMA) moved to lower temperature in comparison with polyNIPAAm

although HEMA is also a hydrophilic comonomer.It was suggested that the formation of hydrogen bonds between the nitrogen atoms in NIPAAm and the hydroxyls in HEMA invoked the phenomenon.Accordingly

a series of poly(NIPAAm-co-DMAAm-co-HEMA) with LCST of ca. 40℃ were prepared in a similar way.These copolymers containing side hydroxyl groups had been used to initial the ring opening polymerization of caprolactone (CL) and poly(NIPAAm-co-DMAAm-co-HEMA) grafted PCL copolymers were obtained.Preliminary studies showed that LCST of the grafted amphiphilic copolymers shifted to lower values with the introduction of hydrophobic PCL chains onto the hydrophilic backbone.Their thermal sensitivity decreased with the amount and length of side PCL chains being increased.Ideally

thermal sensitive micelles prepared from these amphiphilic copolymers would be good candidates for target or “smart" drug controlled delivery to treat diseases

such as solid tumor in combination with local hyperthermia therapy.