Abstract
Poly (N-Isopropylacrylamide-co-2-hydroxyethyl methacrylate) (P(NIPAM-co-HEMA)) was synthesized using ultrasonic irradiation in a mixed solvent of water and ethanol without chemical initiator. Effect of ultrasonic intensity on time courses of conversion ratio, copolymer composition, number average molecular weight, and polydispersity of synthesized polymers was investigated in order to clarify the reaction mechanism of radical copolymerization of temperature-responsive polymer with low molecular weight distribution (i.e., low polydispersity). The reaction kinetic model for ultrasonic synthesis process of P(NIPAM-co-HEMA) was constructed with considering the cross-propagation reaction and cross-termination reaction in the radical copolymerization of NIPAM and HEMA. The experimental results showed that PNIPAM fraction of the copolymer in the early stage was lower than initial NIPAM fraction. Those results suggested that HEMA terminated radical was more stable than NIPAM terminated radical so that consumption rate of NIPAM was slower than that of HEMA. The calculated results supported that the cross propagation reaction between HEMA terminated radical and NIPAM monomer was much slower than that between NIPAM terminated radical and HEMA monomer.
