High Tensile Strength Regenerated α-1,3-Glucan Fiber and Crystal Transition.

α-1,3-Glucan is a linear and crystalline polysaccharide which is synthesized by in vitro enzymatic polymerization from sucrose. A previous study reported that regenerated fibers of α-1,3-glucan were prepared using a wet-spinning method. However, the mechanical properties were poorer than cellulose regenerated fibers. Then, in this study, the mechanical properties of the regenerated α-1,3-glucan fiber were improved by the transformation of the crystal structure and stretching. The regenerated fiber stretched in water and dehydrated by heating showed high tensile strength (18 cN/tex) that is comparable with that of viscose rayon. Moreover, the crystal structures of the regenerated fibers were investigated using wide-angle X-ray diffraction (WAXD). To date, four crystal polymorphs of α-1,3-glucan from polymorph I to IV have been reported. This study revealed that the regenerated α-1,3-glucan fibers had two different polymorphs, polymorph II (hydrated form) and polymorph III (anhydrous form), depending on post-treatment methods of stretching and annealing procedures. Furthermore, the obtained distinctive 2D-WAXD patterns suggested that polymorph III is identical to polymorph IV.