Phase behaviour of liquid crystalline side chain polymers

The phase behaviour of liquid crystalline side chain polymers is investigated by different experimental methods.PVT‐ and DSC‐measurements as well as X‐ray and optical investigations show that additionally to the known factors from low molecular weight liquid crystals the flexibility of the polymer backbone influences the liquid crystalline properties of the phase. Fixing a mesogenic side chain to a polymer backbone leads to a stabilisation or even a generation of a liquid crystalline phase in comparison to the corresponding low molecular weight liquid crystals. — The liquid crystalline phases which are known from low molecular weight liquid crystals are also found for liquid crystalline polymers (nematic, chiral‐nematic, smectic). In contrast to low molecular weight liquid crystals the phase transformations smectic to crystalline and chiralnematic to smectic show strong time dependences for polymeric substances. — A crystallization of the liquid crystalline side chain polymers is observed, when the polymer main chain is so flexible, that the mesogenic groups can form a crystalline order. The crystallization process leads for a smectic sample to a layer lattice structure. From X‐ray investigations one can conclude that the smectic arrangement of the mesogenic side chain exhibits a preorder for the crystalline structure. As known from other substances the crystallization rate depends on temperature and pressure. — The transformations in the liquid crystalline region are first‐order transformations and obey the Clausius‐Clapeyron equation. At lower temperatures all liquid crystalline polymers solidify to anisotropic glasses. Below the glass transition temperature nematic or smectic states of order are frozen‐in and preserved in this way.