Valery Shibaev

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, 10: phase behavior and structure of side-chain liquid crystalline ionomers containing ions of d-metals ☆

Abstract Novel side-chain liquid crystalline (LC) ionomers containing d-metals Co(II) and Ni(II) were synthesized and characterized. Both families of the ionomers are characterized by the same influence of charged group content in polymer on their phase behavior. The incorporation of 2–3xa0mol% of metal ions in the nematic polymer matrix leads to the induction of SmA phase and rise in the clearing point. The peculiarity of their phase behavior in comparison with the earlier investigated LC ionomers with alkaline or alkali-earth metals is the full destruction of the mesophase at the concentration of d-metal higher than 12xa0mol%. This phenomenon was associated with the well-known ability of the transition metal ions to form various complexes that, in the case of LC ionomers, can negatively influence the ordering of the side mesogenic groups. The proposed structure of the LC ionomers is discussed in comparison with the metallomesogenic polymer systems.

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, 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.

Comb-Shaped Liquid-Crystal Polymers

Polymers with a comb-shaped structure were the first representatives of thermotropic LC polymers. The principle of the creation of such systems by chemical addition of molecules or fragments of the mesogenic groups of low-molecular-weight liquid crystals to the polymer chain [1–6] with flexible (usually aliphatic) spacers was subsequently [7] made the basis for the creation of another large class of linear thermotropic LC polymers which consist of macromolecules with alternating flexible and rigid (mesogenic) fragments (cf. Chapter 5).

A Small Angle Neutron Scattering Study of the Effect of Molecular Weight on the Conformation of Side Chain Liquid Crystal Polymers in a Smectic Phase

Abstract The Small Angle Neutron Scattering (SANS) from specifically deuterated samples of side-chain liquid crystal polymers has been used to determine the dimensions of the backbone both parallel and perpendicular to the director as well as the degree of polymerisation. It has been possible to determine the effect of molecular weight on the chain dimensions in the smectic phase. There is strong anisotropy of the backbone conformation and it becomes stronger as the molecular weight increases. This means that the tendency for the chains to be confined between the smectic layers is stronger for larger molecular weight polymers.