(116x) Microwave Assisted Synthesis of Polyethylene Glycol Dimethacrylates and Nuclear Magnetic Resonance Analysis of Water's Interactions with Polyethylene Glycol Dimethacrylate Hydrogels

Hydrogels are water-swollen polymers with applications as controlled release devices for drug delivery and cell scaffolds for tissue engineering. Photopolymerized polyethylene glycol (PEG) is one of the most commonly used hydrogels for these applications. PEG has become the material of choice because of its ability to resist nonspecific protein adsorption. Protein adsorption plays a key role in foreign body and immune responses of any material placed in the body. One of our research goals is to determine why PEG can resist nonspecific protein adsorption so effectively. We hypothesize water's interaction with the individual monomers plays a role in this protein resistance. To this end, we synthesized polyethylene glycol dimethacrylate, a photopolymerizable precursor to hydrogels, by microwave reaction of PEG diol and methacrylic anhydride. Microwave reaction yielded the dimethacrylate within five minutes and over 90% of the diols converted into dimethacrylate. Aqueous solutions of the dimethacrylates were converted to hydrogels with a photoinitiator and Ultra-Violet light. The hydrogels were characterized with FTIR and dried to determine water content in each gel. The actual dynamics of the water with the hydrogel, the effect of photopolymerization time on the polymer relaxations and interactions with water were studied with nuclear magnetic resonance (NMR) measurements.