On the relevance of the 8-chain model and the full-network model for the deformation and failure of networks formed through photopolymerization of multifunctional monomers

Crosslinked networks were synthesized by copolymerization of mono-functional tert-butyl acrylate (tBA) with diethyleneglycol dimethacrylate (DEGDMA) or polyethylene glycol dimethacrylates (PEGDMA). By varying the chain length and concentration of the difunctional PEGDMA, we obtained tBA-PEGDMA copolymer networks while by varying the concentration of difunctional DEGDMA, we obtained tBA-DEGDMA crosslinked networks. The various materials were submitted to large deformations through uniaxial tension tests. For moderate weight percent of cross-linking agent, up to 20%, the networks showed standard S-shape stress-strain curves, characteristic of rubber-like elasticity. Two macromolecular models, the 8-chain model and the full-network model, were applied to fit the uniaxial tensile response of the materials. Both models provide good representations of the overall uniaxial stress-strain response of each material. After fitting to stress-strain data, the network models were employed to predict the shear modulus and the elongation at break. Neither the 8-chain nor the full network model were capable of predicting the failure strain or shear modulus, indicating these models are best used to describe stress-strain relations rather than predict mechanical properties for the network polymers considered here. ©2008 Wiley Periodicals, Inc.