Relationship between physical properties of tetra-PEG gels and polymer chains

Polymer gels are swollen 3D polymer networks. Because a polymer network consists of polymer chains connected by crosslinks, the physico-chemical properties of polymer gels are inherently related to those of a polymer chain. However, the full understanding of these relationships have been inhibited by the inherent heterogeneity of polymer networks. In this paper, in order to discuss the relationship between the mechanical properties of polymer gels and the single polymer chain, we utilize Tetra-PEG gels, which are polymer gels with well-controlled network structures. The ultimate elongation ratio of the Tetra-PEG gels increased with increases in polymer volume fraction and degree of polymerization of network strands, and was independent of the connectivity. These results do not obey the Kuhn model, in which the principal concept is based on a single polymer chain. We propose a new semi-empirical model, where the initial length of a network strand is not defined only by the degree of polymerization of a network strand, but influenced by the polymer volume fraction.