疑似一次元異方性膜を目指した液晶性超高分子多糖類のミクロン配向制御

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The method of fabrication of uniaxially oriented 3-D membranous structures, by evaporating liquid crystalline (LC) polysaccharide solutions from a limited space of 1 mm, had been established. The polysaccharides, xanthan gum and sacran, having high molecular weight and lyotropic LC properties, accumulate at a position, as a nucleus for a thin membrane that subsequently bridges the two substrates and grows with the descending air-LC interface. The role of the LC state and its shape that guides the bridging deposition of the polysaccharide was further examined and the associated rheological characteristics were explored. An aqueous solution of cyanobacterial exopolysaccharide, sacran (a), consisting of rod-shaped LC units deposit to form a 1 mm wide membrane by bridging the gap. In contrast, the solution of another sacran obtained by bulk extraction, sacran (b), containing rod- and platelet-shaped LC units, could bridge an extraordinary thicker gap between the substrates of the drying cell. Strong interactions at the drying air-LC interface help the platelet-shaped units to unequivocally align with the rod-shaped units. The physical insights in this work reinstate the use of LC biopolymers to prepare long-range ordered structures without the use of complicated setup/instruments. Also, it affords a direct indication towards the role of structural units occurring in nature under a perpetually drying environment. This work was recognized and awarded with the Best Poster Award at the Okinawa Colloids International conference.