Comb-shaped liquid crystalline ionogenic copolymers

 A series of new ionogenic liquid crystalline (LC) copolymers (A4CB-AA) was prepared by radical copolymerization of 4-(4-cyanobiphenyl-4′-yloxy) butyl acrylate (A4CB) and acrylic acid (AA). The presence of the AA units do not prevent the development of the nematic phase, which is typical of the initial cyanobiphenyl homopolymer. At a content of AA of 42–52 mol%, the copolymers produce the S _Ad type of mesophase, and this phenomenon is explained by an increased rigidity of the main chain due to the development of intramolecular hydrogen bonds. By increasing the concentration of AA units higher than 55 mol%, the development of mesophase is prevented, and the as-received copolymers are amorphous. A crucial role of intramolecular hydrogen bonds for the development of the S _A phase in the copolymers is proved by synthesizing and studying the copolymers, in which the same type of the mesogenic group A4CB is preserved but the second component is provided by methyl ether of acrylic acid; such copolymers are able to produce only a nematic phase. Studying orientation of LC A4CB-AA copolymers in the magnetic field by the method of wide-line ¹H NMR spectroscopy allows one to calculate the temperature dependences of order parameter S and to advance a correct interpretation of experimental data. Received: 8 January 1998 Accepted: 14 April 1998     

Effect of the tail‐group length and degree of polymerization on the order parameter of side‐chain liquid‐crystalline polymethacrylates containing phenylbenzoate mesogenic groups

The orientation of the side‐chain liquid‐crystalline polymers (LCP) containing phenylbenzoate mesogenic groups in the magnetic field was examined with ²H NMR spectroscopy. The influence of the degree of polymerization as well as the length of the methylene tail group (n = 1–4) have been established. The decrease of the order parameter S of the LCPs with an increased length of the tail group was found. The order parameter S of LCPs does not depend on the degree of polymerization. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2044–2048, 2002     

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.     

Refinement of the crystal structure of (RS)-carnitine hydrochloride

A single crystal of (RS)-carnitine hydrochloride has been obtained, and its crystal structure has been refined by an x-ray structural experiment.     

Side‐chain functionalized liquid crystalline polymers and blends, 2. Phase behavior of comb‐shaped liquid crystalline ionomers containing ions of alkaline metals

An effective way to synthesize liquid crystalline ionomers by an exchange reaction between the acid groups of functionalized LC polymers and a metal acetate was examined. A number of LC ionomers containing ions of the alkaline metals Na and Rb (1.2–18.3 mol‐%) were obtained. The introduction of small amounts (1.2–5 mol‐%) of metal ions into a functionalized LC polymer matrix leads to significant changes in the phase state of copolymers – the nematic phase is replaced by a SmA phase; an increase of the content of alkaline metal ions causes linear growth of clearing temperatures. The influence of the nature of the metal ions on the phase behavior of LC ionomers was determined. To describe the peculiarities of the LC ionomers' phase behavior a model based on the assumption that an ion multiplet is formed was proposed. Here, the rigidity of the functionalized LC copolymer chains used as a matrix for the preparation of LC ionomers was taken into consideration.     

Chiral nematic phase in hydrogen-bonded blends of a side-chain smectic polymer with low molar mass dopants

The possibility of chiral nematic mesophase induction in blends of a smectic A side-chain liquid-crystalline copolymer with low molar mass dopants was studied. The chirality of the initial copolymer was determined by the cholesterol optical active groups; however, in the individual state it was not able to form any chiral liquid-crystalline phases. We have shown that the induction of the chiral nematic phase becomes possible in blends of such a copolymer with low molar mass dopants that are stabilized by hydrogen bonding. Phase behavior and optical properties of the blends were studied with X-ray scattering, differential scanning calorimetry and polarizing microscopy. Owing to hydrogen bonding the blends are stable over a wide range of contents and temperatures. The nature of the end group in the dopant molecules is shown to have an important influence on the chiral mesophase induction concentration and the clearing temperatures of the blends. Temperature and concentration dependences of the selective reflection maximum wavelength in the chiral nematic phase were also studied.

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 S_zz of the nematic phase shown by the nanocomposites increases.     

Effect of hydrogen bonds on orientational order in liquid-crystalline polymers

The orientational behavior of nematic LC copolymers (4-{[6-(acryloyloxy)hexanoyl]oxy}phenyl-4-propoxybenzoate)-co-(4-(6-acryloyloxypropyl-1-oxy)benzoic acid) in a magnetic field has been studied by ²H NMR spectroscopy. An increase in the content of carboxyl groups in the copolymer leads to an appreciable growth of the orientational order parameter S _zz .     

Influence of the Molecular Structure of Comb-Shaped Photochromic Copolymers on Photoinduced Birefringence

A series of mesomorphic and amorphous photochromic copolymers containing azobenzene groups were prepared. The emergence of induced birefringence in films of these copolymers under the action of plane-polarized laser light was studied.     

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 S_zz of the nematic phase shown by the nanocomposites increases.