Abstract
Physical properties of polymer gels are determined by various structural parameters. Although molecular models predicting these properties have been proposed, the systematical understanding is inhibited by inevitable heterogeneity of polymer network structure. Recently, we successfully developed the Tetra-PEG gel with homogeneous network structure and well-controlled network structures. In this review, we introduce our recent studies on the dependence of the structural parameters (connectivity and polymer concentration) on the elastic modulus using the Tetra-PEG gel as a model system. Elastic moduli of the polymer gels prepared around the overlapping concentration is predicted by the phantom network model. The model predicting the elastic modulus shifts from the phantom to the affine network models with an increase in the preparation concentration. Based on the experimental results of the tearing test, uniaxial stretching and swelling test, the elasticity of the Tetra-PEG gel is mainly governed by the chemical crosslinks, and the fluctuation of crosslinks is suppressed increasing the concentration. Conventional molecular models considering the effect of the entanglement, however, cannot predict these results. Further modification of the existing molecular models are desired.
