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

Differential 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.

X-ray investigation of combined main-chain/side-chain liquid-crystalline polymers

Abstract Structural investigations on six combined liquid-crystalline polymers using the X-ray technique are described. The measurements have allowed a characterization of the liquid-crystalline phases and have led to our first ideas about the phase structures. All mesogenic groups are arranged parallel to each other, the shortest segment in the main-chain or in the side-chain determines the smectic layer spacing. A modified designation for liquid-crystalline phases of high polymers is proposed.

X-ray scattering experiments on oriented polysiloxanes with paired mesogens and different distances between these swallow-tailed side groups show a remarkable dependence of the smectic monolayer thickness on the degree of dilution, whereas the interplanar distance of the side groups remain nearly constant. Due to the dominating interaction of the mesogenic moieties, the flexible main chain is forced to take part in the layer formation. A packing model is proposed to explain the results of the X-ray studies. For polymers with five or more dimethylsiloxane copolymer segments, a diffuse scattering appears in the smectic as well as in the isotropic phase. This scattering is independent of the o…

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.