Structure and frustration in liquid crystalline polyacrylates: I. Bulk behavior

The phase behaviour and structure are reported of a new type of frustrated side-chain liquid crystalline (LC)polymer,a polyacrylate with phenylbenzoate mesogenic side groups and a narrow polydispersity. At a high degree of polymerisation the LC polymers show a nematic, a smectic-A_d, a re-entrant nematic and a ˜C phase, for shorter chains only a nematic and a ˜C phase.This constitutes a new example of nematic re-entrance for which the driving field is the length of the polymer chain.The smectic-A_d layers consist of partially overlapped side groups while in the ˜C phase the side chains are rearranged into chevron-like blocks of bilayers.We propose an explanation of the frustrated phase behaviour in terms of these two different competing length scales and their coupling to the backbone conformations.