SYNTHESIS AND CHARACTERIZATION OF NOVEL PEG-TETHERED PMAA HYDROGELS BASED ON A PEG MACROMOLECULAR AZO INITIATOR

摘要

A new route was proposed to synthesize polyethylene glycol-tethered polymethacrylic acid (viz., PEG-tethered PMAA or PEG-t-PMAA) hydrogels based on a macromolecular azo initiator (MAI), PEG-attached azo initiator. The preparation of the MAI was accomplished by coupling PEG with 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (AMHP) using 1,1-methylene bis-(4-isocyanatocyclohexane) (H_(12)MDI) as bridging molecules. The structure and morphologies of the resulting hydrogels were characterized by FTIR and SEM. The pH and ionic strength responses were investigated by swelling measurements, depending on molecular weight (MW) of PEG, molar ratios of isocyanate-terminated PEG to AMHP and mass percentage of the as-prepared MAIs. The PEG-t-PMAA hydrogels synthesized by 100 wt% PEG 1000-attached azo initiators and a molar ratio 2 of-NCO-terminated PEG to AMHP exhibit more remarkable pH and ionic strength response than any other hydrogels. The driving force of swelling is believed to be mainly due to the porosity and dissociation balance of PMAA gels as well as gel compositions, while the deswelling behavior may be correlated with the decrease in osmotic pressure caused by the so-called "charge screening effect" of the cations. The PEG-t-PMAA hydrogels are expected to find specific applications in oral drug delivery and tissue engineering.