Static and in situ small-angle X-ray scattering analyses of the effect of molecular structure on the tensile properties of cross-linked curdlan hydrogels and stretched, dried gel-films

Random-coil and triple-helix curdlan hydrogels cross-linked with ethylene glycol diglycidyl ether were fabricated using curdlan alkaline solutions with different concentrations. Triple-helix hydrogels had higher tensile strengths than random-coil hydrogels. Small-angle-X-ray scattering analyses revealed that triple-helix hydrogels contained aggregates, which were likely bundles of triple helices. Moreover, in situ small-angle-X-ray scattering analyses indicated orientation of these triple-helix bundles during elongation. Cross-linked curdlan hydrogels were stretched up to 3 times and subsequently dried to prepare stretched, dried gel-films. Triple-helix dried gel-films exhibited a maximum strength of 200 MPa, which was markedly higher than that of random-coil dried gel-films. Triple-helix curdlan hydrogels and dried gel-films exhibited higher tensile strengths than their random-coil counterparts, suggesting that triple-helix bundles underwent crystallization and orientation.