Preparation And Characterization Of Dual Sensitive Graft Copolymer

Using azobisisobutyronitrile (AIBN) as an initiator and mercaptopronic acid (MPA) as a chain transfer reagent, oligo (N-isopropylacrylamide) with a functional end was synthesized by radical solution polymerization. Then, using DCC(Dicyclohexyl carbodiimide) and DMAP((iV, N '-Dimethyl aminopyridine) as dehydration catalyst, PNIPAAm [Poly (N-isopropylacrylamide)] macromonomer ( PNIPAAm- HEMA ) was prepared by the esterification of oligo (N-isopropylacrylamide) and 2-hydroxylethyl methacrylate. Finally, using MAA (methacrylic acid) and PNIPAAm macromonomer, PMAA-g-PNIPAAm copolymer was prepared by the methods of radical solution copolymerization. All the products was characterized by FT-IR spectra , NMR spectra and GPC. The results indicate that this synthesis method has many advantages, such as mild reactive condition. This method is favorable in laboratory synthesis.Phase transition behavior of this graft copolymers in aqueous solution are investigated using the optical transmittance of the copolymers in the aqueous solution by UV-Vis instrument. When the pH value is below the pKa of PMAA, the graft copolymers are not soluble. Once the pH value is above the pKa of PMAA, the graft copolymers have their lower critical solution temperatrure (LCST). But when the pH value is above 7.0, the graft copolymers can be soluble despite of the change of the temperature.