Preparation of transparent self-standing thin films made from acetylated euglenoid β-1,3-glucans.

The feasibility of using acetylparamylon to prepare self-standing optical films was investigated. Its thermal stability, represented by the glass transition temperature, and 5% weight loss temperature are equivalent to those of acetylcellulose. The mechanical properties (maximum stress, elongation at break, and elastic modulus) of acetylparamylon films prepared by solution casting were comparable to those of acetylcellulose films. The degrees of their transparency and birefringence were the same as those of the acetylcellulose film. These results, together with the finding that acetylparamylon with a higher degree of acetylation formed a thin film with fewer micrometer-sized defects and that acetylparamylon with a lower degree of acetylation formed a thin film with a nanometer-level flat surface, suggest that acetylparamylon is a feasible material for self-standing optical film.