I. I. Konstantinov

Preparation of Polymer-Nanodiamond Composites with Improved Properties

An efficient method is developed to achieve improved dispersion of detonation nanodiamond particles in amorphous thermoplastic matrices. For an estimation of the nanodiamond distribution in slices, a method of optical and transmission electron microscopy is used. The complex set of mechanical properties of polymer-nanodiamond composites is considered: tensile properties, Izod impact strength and Brinell hardness. It is found that the reinforcing and toughening effects of uniformly-dispersed nanoparticles on polymer matrices is pronounced at lower loading compared with traditional mixing procedure.

Synthesis and characterization of new chiral mesogenic monomers

Abstract New mesogenic monomers carrying substituted biphenylyl rings linked to acryloyl or methacryloyl moieties through straight or chiral flexible spacers have been synthesized. All the investigated monomers, independent of the side group chirality, have been found to form ordered smectic phases, most probably of the S1 type. The asymmetric methyl substitution on the flexible spacer leads to an expansion of the temperature range of mesophase stability. The chiral monomers induce a helical structure when mixed with appropriate nematogens. The fingerprint texture of a contact mixture of the chiral methacrylate prepared in this work, with a nematic methacrylate synthesized previously, has been found not to change after UV-initiated polymerization.

Structure of polymers with phenyl benzoate side groups by X-ray evidence

Abstract Structure of four polymers were studied: poly-p-methacryloyloxy phenyl esters of p-n-hexyloxy benzoic acid (PMB-6), p-n-heptyl benzoic acid (PMH-7) and p-n-heptyl - trans-cyclohexane carboxylyc acid (PMC-7) and poly-p-n-hexyloxy phenyl ester of pmethacryloyloxy benzoic acid (PM-06). Diffractions parameters and polymer organization were discussed in terms of both crystallinity and paracrystal. The structural organization of PMB-6, PMH-7 and PM-06 was interpreted on the basis of block model. Structure of PMC-7 assumed to be organized similar to cybotactic nematics.

Combining carbon and polymeric particles in an inert fluid as a promising approach to synthesis of nanocomposites

Effective method for introduction of dispersed filler particles into a polymeric matrix was developed. The method is based on disaggregation and uniform deposition of the filler onto the surface of polymeric particles in an inert liquid medium under the action of ultrasound. Particles of detonation nanodiamond were used as the filler.

Rheological evidence for the existence of subphases in the liquid crystalline 4-n-alkoxybenzoic acids

ABSTRACT The rheological behaviour of the homologous series, the alkyloxybenzoic acids, has been studied at steady flow and small amplitude oscillatory shear. The temperature dependencies of the viscosity were compared with differential scanning calorimetry data in order to estimate pretransitional phenomena in mesophases. The values of the viscosity and flow activation energy (E) can be indicative of the mesophase state. 4-n-pentyloxybenzoic acid yields a classic nematic (N) phase while the next homologues show a cybotactic nematic phase having a higher E value. The N phase is a Newtonian fluid of lower viscosity than that of the isotropic phase. The cybotactic nematic phase by its rheological properties takes an intermediate position between the N phase and a smectic C (SmC) phase. The SmC phase is a viscoelastic and viscoplastic medium. The SmC phase of 4-n-octyloxy-, 4-n-nonyloxy-, 4-n-decyloxy- and 4-n-dodecyloxybenzoic acid can exist in high- and low-ordered states. The more ordered smectic phase is characterised by higher stiffness, viscosity and yield stress than those of the less ordered. The SmC phase of 4-n-hexadecyloxybenzoic acid is characterised by the only state with unstable value of apparent viscosity. The phase state and the transition temperature can be dependent on the thermal history of the sample and a mechanical shear. GRAPHICAL ABSTRACT

IR dichroism study of orientational ordering of liquid-crystalline acrylates

Orientational ordering of four liquid-crystalline acrylates induced by the surface of KBr plates over a wide temperature range was studied by the IR dichroism technique. IR spectra of homogeneously aligned samples were used to calculate the angles between the direction of the transition moment for a series of vibrations of the mesogenic fragment and its long axis. A method for calculation of the homeotropic orientation parameter of molecules was proposed. The orientation parameters of homogeneously and homeotropically aligned samples in the nematic, smectic (A), and chiral smectic (I andH) phases were calculated. Thein situ photopolymerization of acrylates in the smectic phases occurs with retention of the orientational ordering in the polymer films formed.

A New Chiral LC Acrylate that Exhibits Pyroelectricity

Abstract The new material (R)-4-(5-acryloyloxy-4-methylpentanoyloxy)-4′-octanoyloxy biphenyl has been synthesised and characterised by POM, DSC, X-ray diffraction, IR dichroism, pyro- and piezoelectric techniques. The acrylate was shown to exhibit direct isotropic to smectic H* phase transition. The natural texture of the H* phase separates from the isotropic phase in the form of bâtonnets and rounded domains, the latter develop into a mosaic. The mesophase was found to align in a thin cell of KBr plates with homeotropic anchoring independently of the type of surface treatment. The molecular organisation in the H* phase strongly favours fast and efficient polymerisation when the initial orientation retains upon the reaction. The structure of the crystal and H* phases is mono-layer, the molecules pack monoclinic in antiparallel fashion with long-range polar ordering. The pyroelectric coefficient was found to be very high in the crystal (γ = 2.0÷2.9 nC/cm2·K) and H* (γ = 2.9÷1.0 nC/cm2·K) phases. The direct...

X-ray diffraction study of mesogenic 4-methoxyphenyl-4′-n-nonyloxybenzoate

ABSTRACT 4-methoxyphenyl-4′-n-nonyloxybenzoate have been investigated by single crystal X-ray structural analysis. Crystal packing of the compounds does not represent a precursor of the mesophse although the typical for liquid crystal compounds separation of crystal packing on aromatic and aliphatic areas is observed here. Possible reason for monotropic properties are discussed.

X-ray diffraction and DSC study of 4-n-butyloxyphenyl 4′-hydroxybenzoate

ABSTRACT 4-n-Butyloxyphenyl 4′-hydroxybenzoate C4H9−O−C6H4−(O)OC−C6H4−OH have been investigated by single crystal X-ray structural analysis and DSC measurements. Crystal packing of the compounds and possible phase transitions are discussed.

New chiral LC acrylates: Polar ordering in crystal and smectic phases

Abstract Two mesogenic acrylates derived from (R)-5-bromo-4-methylpenta-noic acid, having biphenyl moiety, have been synthesised and characterised by POM, DSC, X-ray, pyro- and piezoelectric techniques. The only real difference in molecular structure of the compounds is that the one contains terminal octyloxy group (1) and the other has octanoyloxy group (2). Crystal structures of the acrylates were shown to be precursors of tilted smectic phases. Both compounds are manomorphic exhibiting either smectic I* phase (1) or smectic crystal H* phase (2). 1 crystallises in non-polar space group while the crystallisation of 2 yields crystals with a polar axis. Good correlations were found in electric responses between the crystalline phases and mesophases of both the acrylates.