Synthesis and characterization of oligo(poly(ethylene glycol) fumarate) macromer

A novel oligomer based on alternating fumaric acid and poly(ethylene glycol ) (PEG) units was synthesized and characterized. End group analysis by nucl ear magnetic resonance (NMR) spectroscopy showed that the oligo (PEG fumara te) (OPF) had end PEG chains and multiple fumarate groups along its macromo lecular chain. According to thermal characterization by differential scanni ng calorimetry (DSC), the crystallinity of OFF was found to be lower than P EG. The molecular weight and the degree of oligomerization of OFF determine d by gel permeation chromatography (GPC) revealed that the conversion of OF F was substantially affected by the steric factors associated with large PE G chains. OFF was cross-linked using radical polymerization in the presence of either a chemical initiator or photoinitiator. As the OFF cross-linked, the unsaturated fumarate bonds disappeared and the PEG proton peak broaden ed in the NMR spectra. The cross-linked OFF gel showed swelling behavior th at was dependent on the molecular weight of PEG. This novel cross-linkable PEG macromer is the first macromer with unsaturated double bonds along its macromolecular chain that allows for the preparation of hydrogels with tail ored structure and properties.