Photochemical Sythesis Of 2-Hydroxyethyl Methacrylate Copolymer And IPN Hydrogels And Their Properties

In recent years, considerable research attention has been focused on the environment-sensitive hydrogels (intelligent hydrogels) because they possess great potential applications in many aspects, including drug delivery system, enzyme immobilization and biomaterials separation and purification, etc. Among them, the pH-sensitive, thermosensitive and pH/temperature responsive hydrogels have been attracted great interest from both fundamental and application fields at present. A series of the hydrogel materials were synthesized with the copolymerization and interpenetrating polymer network (IPN) of DMAA and 2-hydroxyethyl methacrylate (HEMA) by the photochemical technique. The following are main conclusions of our work:1. DMAA/HEMA copolymer and IPN hydrogels were synthesized by photocrosslinking using DMAA and HEMA as monomers, using Irgacure651 as a photoinitiator, and using N,N-methylene bisacrylamide (MBA) as a crosslinker. The hydrogels were characterized by FT-IR, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). Effects of irradiation intensity, irradiation time, monomer concentration, initiator concentration and crosslinker concentration on the swelling ratios of the hydrogels were investigated. The Swelling kinetics and the yield were tested, thus the best experiment condition were accepted with high the swelling ratio and the yield.2. Swelling and deswelling kinetics of P(DMAA-co-HEMA) hydrogels with different monomer ratios were investgated. Compareing with Swelling and Deswelling kinetics of PDMAA/P(HEMA) IPN hydrogels, we found that the swelling and deswelling velocity were bigger than that of the copolymer hydrogels respectively. Equilibrium swelling ratio (ESR) of the hydrgels decreased with temperature increasing. The swelling ratio of hydrogels in high temperature is higher than that in low temperature, and it has good thermosensibility. The copolymer hydregels swelled in the acid medium and shrunk in the alkaline medium and showed pH-sensitive behaviors. Ionic strength has only a small influence on ESR and the swelling ratio decreased gradually when the ionic strength increased.3. After selecting experiment conditions, the controlled kinetics of the photopolymerization of HEMA mediated by HTEMPO systems in the solution have been studied using Irgacure651 as an initiator at ambient temperature. It was found that plots of conversion and ln([M]₀/[M]) vs. time were liner respectively in the photopolymerization of n-BMA in the solution with HTEMPO used as a mediator. However, the number average molecular weight did not increase linearly with monomer conversion, whereas the the polydispersity indexes (PDI) were less than 1.5. Thus, the photopolymerization of n-BMA in the solution didn't controlled.