Structure and physical properties of dried Tetra-PEG gel

We investigated crystal structure, and thermal, swelling, and deformation behaviors of dried tetra-functional (polyethylene glycol) gel, Tetra-PEG gel, with narrow molecular distribution. Tetra-PEG gel consists of two kinds of symmetrical tetrahedron-like PEG macromonomers with a fixed molecular weight. In spite of network structure with rather small molecular weight between cross-links (M(c)) (approximate to 5000), the dried Tetra-PEG gels were found to be capable of crystallization. The crystalline melting temperature (T(m)) and the degree of crystallinity (X(c)) of dried Tetra-PEG gels obtained by differential scanning calorimetry (DSC) were substantially constant against the polymer volume fraction at preparation (phi(0)). Furthermore, the corrected elastic modulus (G) of dried Tetra-PEG gels did not depend on phi(0). These experimental results indicate that the there exist negligible entanglements in the dried Tetra-PEG network irrespective of phi(0). In other words, Tetra-PEG gels do not have significant topological inhomogeneities. (C) 2011 Elsevier Ltd. All rights reserved.