Search results for "Pendant group"

Infrared spectroscopic study of a phenyl benzoate side group—methacrylate main chain polymeric liquid crystal

1994

Abstract The temperature dependence of the infrared dichroism of a side chain polymeric liquid crystal was investigated for two homogeneously oriented samples, one aligned with a PVA coating and the other aligned by a magnetic field. From the apparent order parameters, it was found that the rotation of the mesogenic side group was restricted. Not only the rigid part of the side group, but also the alkyl chains were found to be partly ordered. Realignment of the side groups was observed in the case of the magnetically aligned sample at the smectic-nematic transition temperature. Unlike the other absorption bands, the C˭O bond vibration band shifted to higher wavenumbers with increasing tempe…

The effect of macromolecular architecture of ethylene copolymers with multi-alkenylsilsesquioxane on morphological, rheological and dynamic mechanica…

2021

Abstract The influence of the degree and the way of incorporation of multi-alkenylsilsesquioxane into the polymer chain on morphological, rheological and dynamic mechanical parameters were determined. It was found that POSS incorporated into the polymer chain was located outside the crystalline structure of lamella in amorphous phase. The incorporation of POSS-6-2 as a pendant group resulted in significant increase of separation of macromolecules. The key factor in rheological and dynamic mechanical behavior of copolymers turned out to be the way of POSS incorporation into the polymer chain. The incorporation of POSS into the polymer chain as a pendant group resulted in decreased relaxation…

1995

Redoxactive liquid crystalline (LC) side group polymers were prepared by copolymerization of liquid crystalline acrylates and ferrocene-containing acrylates. The corresponding liquid crystalline ionomers were synthesized by a reversible redox reaction. The incorporation of tetra-alkylated ferrocene derivatives leads to LC polymers with reduced redox potential. These polymers can be oxidized under mild conditions to the corresponding ionomers, which are much more stable in solution than LC ionomers containing monoalkylated ferrocenium ions. Dynamic mechanical measurements and small angle X-ray scattering (SAXS) perfomed on LC ionomers prove the existence of ionic superstructures (clusters) w…

Dimesogenic liquid crystalline oligosiloxanes

1995

Abstract In this paper, the syntheses, phase properties and ferroelectric properties of new liquid crystalline oligosiloxane dimesogens are described. Smectic phases are dominant in this class of materials. Spontaneous polarizations are in the range of 10 to approximately 100 nCcm−2. The materials show interesting properties for display applications. Although offering higher mechanical stability than low molar mass materials, their switching is significantly faster (switching times in the range of some 10−5s) than is the case for similar side group polymers (typically some 10−3s). Therefore these new oligosiloxane derivatives may be ideal for building flexible displays. In addition, mixture…

1984

The synthesis and phase behaviour of azo dye containing liquid crystalline side group copolymers are described. These Copolymers show the same electro-optical effects as low molar mass guest-host systems. Their macroscopic oriented nematic structure can be frozen in below the glass transition temperature resulting in a polymer film with dichroic properties. The behaviour of the copolymers (phase behaviour, surface and electric field orientation) can be improved via mixtures with low molar mass liquid crystals.

1985

Comparaison de deux polyarylates nitrile ayant des groupes d'espace differents [(CH 2 ) 2 ou (CH 2 ) 6 ]

1986

Preparation d'oligosiloxanes et de polyarylates avec des groupes mesogenes fixes lateralement

Molecular dynamics of solid polymers as revealed by deuteron NMR

1983

Pulsed deuteron NMR spectroscopy is described, which has recently been developed to become a powerful tool for studying molecular dynamics in solid polymers. It is shown that by analyzing the line shapes of2H absorption spectra and spectra obtained via solid echo and spin alignment, respectively, both type and timescale of rotational motions can be determined over an extraordinary wide range of characteristic frequencies, approximately 10 MHz to 1 Hz. By applying these techniques to selectively deuterated polymers, motional mechanisms involving different segments of the monomer unit can be monitored. In addition, motional heterogeneities in glassy polymers can be detected. The information a…

1984

The fiber patterns of a series of liquid crystalline polymers were analysed. For polymers with smectic phases and for polymers with long spacers and nematic phases, the mesogenic groups orient perpendicularly to the polymer main chains which are parallel to the fiber axis. The fiber pattern indicate a short range order of the mesogenic groups analogous to that in low-molecular weight liquid crystals. For polymers with short spacer groups and nematic phases qualitatively different fiber patterns are found. These fiber patterns are indicative for a special nematic phase formed by ribbon-like molecules.

1986

Covalently crosslinked liquid crystalline networks with elastic properties were prepared in isotropic solution from linear liquid crystalline polymers. As linear precursors for the networks were used: (i) polymers with the mesogenic groups in the side groups (polyacrylates and polymethacrylates), (ii) polymers with the mesogenic groups in the main chain (polymalonates) and (iii) polymers with the mesogenic groups in main chain and side groups (“combined liquid crystalline polymers”). In all crosslinked polymers the liquid crystalline phases of the linear polymers are retained. For low degrees of crosslinking (≤2 mol-%) the phase transition temperatures remain nearly unchanged. These elastom…