Marina Barmatova

Influence of silver nanoparticles on the order parameter of liquid crystalline polymers

New polymer nematic nanocomposites are prepared containing 1.43–4.64 wt % of silver nanoparticles whose mean dimensions are 2–4 nm. According to 2H NMR spectroscopic measurements, on increasing the content of metallic nanoparticles, the orientational order parameter Szz of the nematic phase shown by the nanocomposites increases.

Preliminary communication Induction of the smectic phase in comb-shaped liquid crystalline ionogenic copolymers by hydrogen bond formation

Using a radical copolymerization of 4-(4-cyanobiphenyl-4-yloxy)butyl acrylate and acrylic acid, a number of new liquid crystalline ionogenic copolymers capable of hydrogen bonding were synthesized. The formation of hydrogen bonds results in an invariant temperature interval of existence for the LC state (up to 52mol% of acrylic acid) and a rather sudden replacement of the nematic phase by the SmA phase with increase in content of acrylic acid (35 mol%) in copolymers.

Side‐chain functionalized liquid crystalline polymers and blends, 6. Phase behavior, structure and magnetic properties of Cu(II) containing liquid crystalline ionomers

The new series of the LC ionomers containing copper ions has been obtained and their phase behavior has been studied. It was shown that at low metal ion concentrations in the LC ionomers (˜2 mol-%) the induction of the SmA phase is observed. An increase in the copper ion concentration is accompanied by a slight rise in clearing and glass transition temperatures. The magnetic properties of LC ionomers were studied at the first time. It was shown that LC ionomers are antiferromagneties with a strong exchange interaction J = 174–178 cm–1. Temperature dependencies of the magnetic moment and the magnetic anisotropy are adequately described in the framework of the 1-D-Heisenberg linear-chain model.

Side chain functionalized liquid crystalline polymers and blends, 1. Reentrant nematic phase formation in hydrogen‐bonded blends of liquid crystalline functionalized copolymers with a low molecular weight non‐mesogeic dopant

Hydrogen-bonded blends based on smectic comb-shaped functionalized LC copolymers containing alkyloxy-4-hydroxybenzoic acid fragments (proton donor) and the low molecular weight dopant 4-(4-pyridyloyl)cyanobenzoate (proton acceptor) were obtained. It was observed that blends containing 10–25 mol-% of low molecular weight dopants form a reentrant nematic phase (SmA-RN-SmA-I). The blend behavior in the magnetic field was studied, and the orientational elastic constants of the RN phase were determined.

Side-chain functionalized liquid crystalline polymers and blends, 5. Order parameter for hydrogen-bonded blends of the functionalized liquid crystalline polymer with a low molecular weight dopant

A hydrogen-bonded blend based on comb-shaped functionalized LC copolymers containing alkyloxy-4-hydroxybenzoic acid fragments (proton donor) and a low molecular weight dopant 4-(4-pyridyloyl)methoxybenzoate-d 4 (proton acceptor) was obtained. The temperature dependence of the order parameter S, the birefringence Δn and the bend elastic constant K 3 of the LC copolymer and blend were studied by the 2 H NMR spectorscopy and the Fredericksz method of threshold transitions in a magnetic field. The formation of the blend leads to a decrease of the order parameter S of the functionalized LC copolymer. The essential difference in the order parameter S of the mesogenic groups of the LC copolymers and the dopant molecules was established.

Optical isotropic mesophase in side chain copolymers containing isophthalic acid groups

Random side chain copolymers, containing cyanobiphenyl mesogenic units and 37–58 mol % of isophthalic acid monomer units, possess an unusual ability to produce optically isotropic mesophases. This is demonstrated by the absence of birefringence and by high optical transparency of their films. At the same time, corresponding DSC curves show a well pronounced first order transition with a heat of fusion of 1.5–2.34 kJ mol−1. A key reason behind the formation of an optically isotropic mesophase is likely to be related to the microphase separation between side groups of the copolymers.

Side-chain functionalized liquid crystalline polymers and blends, 3. Effect of intra- and intermolecular hydrogen bonds on the order parameter and elasticity constants of side-chain functionalized LC polymers

New series of functionalized side-chain LC polymers were synthesized. They contain phenyl benzoate mesogenic groups and functional carboxylic groups, derivatives of alkyloxybenzole acid, with different numbers of methylene groups in the spacer (n = 3, 6, and 9). The effect of hydrogen bonds on the phase state and the structure of LC polymers is shown. It was found that the increase in the length of the flexible fragment in the functional monomer and (n = 6 of 9) favors the formation of intermolecular hydrogen bonds. In the case of a short spacer (n = 3), predominantly intramolecular hydrogen bonds are formed. The formation of intra- and intermolecular hydrogen bounds influences the values and the temperature dependences of birefrigence, the order parameter and orientational elastic constants for the nematic phase of the LC copolymers.

New Principle of Molecular Design of LC Polymers by Covalent and Ionic Bonding of Side Groups

Abstract The combined principle to design comb-shaped LC polymers by covalent and ionic bonding of side groups with the main chain was suggested. The ionic complexes formed by a LC copolymers containing -29 mol % of acrylic acid and octadecylamine were received. A study of phase behaviour of ionic complexes revealed the role that a low-molecular non-mesogenic component, attached through a non-covalent linkage to the main chain of the polymer, can play in the structure and properties of such ionic complexes.

Side‐chain functionalized liquid crystalline polymers and blends, 4. Phase behavior of functionalized liquid crystalline copolymers containing maleic acid fragments

A number of new functionalized LC copolymers contaning mesogenic oxycyanobiphenyl groups and 3-41 mol-% of maleic acid has been obtained by free radical copolymerization in solution. A significant effect of intramolecular hydrogen bonds on the phase behavior of these copolymers is observed, for a maleic acid content of up to 8 mol-% LC copolymers form only the nematic and between 10-41 mol-% the SmA phase is formed. The process of formation of anhydrides in functionalized LC polymers at 130°C is instigated. It is show a that the formation of five-membered intramolecular anhydride rings does not influence the phase behavior of the LC polymers.