Hemiphasmidic Side-Chain Liquid Crystalline Polymer: From Smectic C Phase to Columnar Phase with a Bundle of Chains as Its Building Block.

Abstract

We synthesized a new hemiphasmidic side-chain liquid crystalline polymer (P-n, n is the number of carbons in alky tail of the side chain, n = 4-12) using free radical polymerization. The side chain of P-n has a biphenyl in the middle, linked to the polystyrene backbone and to the terminal phenyl group with three alkyl tails via only methyleneoxy units. Upon increasing n, the mesophase of P-n changes from bilayer smectic C to hexagonal columnar (Φh) phase with the a-dimension of ∼6 nm. Both of the mesophases are long-range ordered, which can be well aligned by simple shearing. The oriented Φh shows a quite low rotational disorder around the shear direction. Most likely, the Φh phase takes a bundle of chains (e.g., ∼five chains) rather than a single chain as its building block. This "multi-chain model" of the Φh phase may represent a new type of self-assembly in side-chain polymers.