Evaluation of the network parameter in aliphatic poly(urethane dimethacrylate)s by dynamic thermal analysis

The dicarbamates obtained from monomethacrylates of oligoethylene glycols and aliphatic diisocyanates were polymerised free radically to form crosslinked polymers consisting of primary chains, crosslinks and pendant side chains bearing unreacted methacrylate groups. The polymers were examined by dynamic mechanical thermal analysis (DMTA) to yield values of glass transition temperature and storage modulus. The latter enabled the network parameters for individual polymers to be evaluated. These have been found to be low when compared with molecular weights of the monomers and can be attributed to intermolecular interactions between the pendant chains and the crosslinks involving urethane linkages. This finding is supported by the ¹H NMR experiments on monomers in solution.