Transitional properties of liquid‐crystalline side‐chain polymers derived from poly(p‐hydroxystyrene)

A series of liquid‐crystalline polystyrene derivatives with ω‐(4‐(4‐fluorophenylazo)phenoxy)‐alkoxy pendant groups have been synthesized and characterized. Homologues with four or more methylene units in the spacer chain exhibit smectic liquid‐crystalline phases, while the homologue with three methylene units forms an amorphous glass. The smectic A‐isotropic (SA‐I) transition temperatures show a marked odd‐even effect as a function of the parity of the spacer chain. This odd‐even behaviour is also found in the variation of ΔS/R at the SA‐I transition across the series. A marked hysteresis between the transition temperatures determined on heating and the transition temperatures determined on cooling is observed. A molecular interpretation of these phenomena is proposed.