Preparation and Properties of Polyurethane Hydrogels Based on Methylene Diphenyl Diisocyanate/Polycaprolactone-Polyethylene Glycol

Polyurethane (PU) hydrogel is an important biomedical material for drug controlled release systems, wound dressings and medical bandages. Three series of polyurethane prepolymers based on methylene diphenyl diisocyanate (MDI), polycaprolactone (PCL) and polyethylene glycol (PEG), using diethylene glycol (DEG), N-methyldiethanolamine (MDEA) or dimethylolpropionic acid (DMPA), as the chain-extender, were prepared. Then the polyurethane hydrogels were obtained from the prepolymers, using benzoyl peroxide (BPO) as a cross-linking agent, by free radical polymerization. The influences of the types of chain-extenders and polyols on the contact angle, swelling ratio and morphology of the polyurethane hydrogels were investigated. The effect ofthe variety of the chain-extendersinthe PU hydrogel on the drug release behavior was also studied. The FT-IR results showed that the PU hydrogels were successfully synthesized. The introduction of PEG improved the hydrophilicity of the PU hydrogels. The MDI/PCL-PEG/DEG hydrogel was hydrophobic, and there were small micropores on its surface; while the MDI/PCL-PEG/DMPA and MDI/PCL-PEG/MDEA hydrogels had high hydrophilicity and a micropouous structure on their surface due to the existence of carboxyl and tertiary amino functional groups. The change of chain-extenders had no significant effect on the cumulative drug release of chloramphenicol from the PU hydrogels. However, the introduction of PEG increased the drug release rate. The chloramphenicol release kinetics from the MDI/PCL-PEG hydrogels indicated non-Fickian diffusion.