Thermal Expansion Coefficient of Curdlan Tripropionate Measured by Thermal Mechanical Analysis and Wide‐Angle X‐Ray Diffraction

Curdlan tripropionate, a crystalline thermoplastic derived from microbial polysaccharide curdlan, is a promising biomass plastic. However, its thermal expansion behavior has not yet been investigated, which is crucial for material design. In this study, amorphous, oriented amorphous, and oriented crystalline films of curdlan tripropionate were prepared, and their thermal expansion coefficients were measured using thermal mechanical analysis. Real‐time wide‐angle X‐ray diffraction measurements at a synchrotron were performed during heating of the oriented crystalline films to evaluate the thermal expansion of the crystal lattice. The coefficient of linear thermal expansion (CLTE) of the amorphous film increased markedly near the glass transition temperature ( T g ≈ 110°C), whereas the oriented crystalline film exhibited largely reversible changes during heating and cooling. WAXD analysis revealed anisotropic lattice expansion, with a significantly larger change along the c ‐axis than along the a ‐axis, and a transition near T g . These results indicate that the thermal deformation of the oriented crystalline film is governed by cooperative interactions between crystalline and amorphous regions, where the crystal framework constrains macroscopic deformation even above T g . This information will be useful for the preparation of blends of curdlan tripropionate and other polysaccharide esters, and for the design of packaging, molding, and electronic substrates.