Effect of Flexible Spacer and Alkyl Tail Length on the Liquid Crystalline Phase Behavior of Fullerene Block Molecules.

Abstract

Here the supramolecular liquid crystalline (LC) phase behavior of a series of fullerene block molecules was investigated regarding spacer length, alkyl tail length and temperature. These compounds exhibit several lamellar LC phases with different packings of self-organized fullerene two-dimensional (2D) crystals. With a short hexamethylene spacer, they form sandwich-like structures with triple or quadruple fullerene layers. By increasing the spacer length to 10 or 12 carbons, a composite layers-in-lamella superlattice structure with alternating soft hydrocarbon single layers and fullerene single or double layers was obtained. As the molecular configurational freedom between incompatible moieties was enhanced by the elongated spacer, the required cross-sectional fullerene-to-hydrocarbon ratio for the superlattice could be achieved despite of different volume fractions of the blocks. The superlattice phase range is efficiently widened by the design principle of constructing LC molecules with a long spacer, which also provides a facile way to tailor novel superstructures.