Bernd Hisgen

Synthesis, structure and properties of liquid crystalline polymers

A number of new liquid crystalline polymers have been synthesized and their mesophase behaviour studied. Two different approaches have been chosen to chemically vary the classical thermotropic side group polymers in order to obtain more insight into the structure—property—relationships of these molecules. (i) The constituents (polymer main chain, spacer and mesogenic units) have been widely varied. Thus, side group polymers with polyester main chains, spacers with oligoethylene oxide or siloxane units, non—mesogenic comonomers (dyes), and disc— like mesogenic units (as side groups as well as within the polymer main chain) have been investigated. (ii) The structural principles of liquid crystalline polymers have been varied by synthesizing side group polymers with paired mesogens (containing two mesogenic units per monomer unit) and of combined main chain and side group polymers (containing mesogenic units as side groups and within the polymer main chain).

Structure and Dilution of Mesogenic Side Chains in Liquid Crystalline Polysiloxanes

Abstract The structure of the smectic phases in four series of homo- and copolymers based on dimethylsiloxane chains with a definite variation of the concentration of the paired mesogenic side chains has been investigated by means of X-ray methods. The dilution of the mesogenic moiety was achieved by insertion of additional dimethylsiloxane segments. A nearly linear dependence of the layer spacings on the dilution has been found. A model of the structure is proposed which consists of two sublayers one of which contains the irregularly arranged main chain whereas the other one is formed by the side chains.

Study of the micro-phase separation in LC-polymers with paired mesogens

SummaryDifferential scanning calorimetry and miscibility investigations were used to study the micro-phase separation of liquid-crystalline dimesogenic side-group polysiloxanes. Diluted co-polysiloxanes exhibit two glass transition temperatures and an unusual miscibility behavior. The observed biphasic character is compared with that of certain amphiphilic systems.