Nigeran (α-1,3-alt-α-1,4-glucan) is a linear glucan with alternating α-1,3- and α-1,4-glycosidic linkages. It is extracted from the cell walls of certain species in the genera Aspergillus and Penicillium. Nigeran can be esterified and used as a film, but its strength is only approximately 4–25 MPa. However, in the present study, high-strength nigeran ester films with tensile strengths of 100 MPa were successfully prepared by thermally stretching and annealing the melt-quenched films. Two-dimensional wide-angle X-ray diffraction (2D-WAXD) analysis revealed that the highly oriented films of nigeran butyrate (NGBu), nigeran valerate (NGVa), and nigeran hexanoate (NGHx) studied herein had two-fold helix symmetry along the molecular axis. Assuming the crystal systems to be orthorhombic, the unit lattice of each ester was calculated as NGBu (a=28.6Å, b=9.07Å, c=16.5Å), NGVa (a=31.5Å, b=9.07Å, c=16.2Å), and NGHx (a=36.7Å, b=9.07Å, c=16.2Å). In the calculated unit lattice parameters, only the a-axis was extended as the number of ester carbons increased.

Cyclic hexamers consisting of a 4-octyl, 4-octyloxy and 4-(2-ethylhexyloxy)triphenylamine unit were synthesized via a Buchwald-Hartwig cross coupling reaction using A-A, and B-B type monomers in order to avoid the formation of other cyclic oligomers such as a pentamer and a heptamer. Unlike different size of cyclic oligomers, all hexamers we examined showed clear cold crystallization in 165-240°C in the DSC thermograms. Resulting oligomers were characterized and applied to hole transporting active layer in an organic field effect transistor. The hexamer with 4-octyl groups exhibited the highest field effect hole mobility (1.99 ×10^-3 cm² V^-1s^-1).

Cyclic oligomers including penta-, hexa-, and heptamer (COTPAs-5, 6, and 7, respectively), where 4-octyltriphenylamine units directly links together at 4,4’-positions, were isolated and characterized as hole transporting materials. With the increase of the macrocyclic size, wavelengths of absorption maximum and edge showed red-shift resulting from the increase of effective conjugation length. It is noteworthy that Stokes shift decreased with the size. SCLC hole mobilities in COTPAs-5, 6 and 7 were estimated to be 1.82 × 10^-5, 1.20 × 10^-4 and 5.11 × 10^-5 cm²/Vs, respectively, which was higher than that of linear polymeric analogue (1.67 × 10^-6 cm²/Vs).