The relationships between liquid crystallinity and hydrogen bonding are studied in mixtures containing 4-pentoxybenzoic acid, 5OBA, and five bipyridines, XBiPy, with spacers having different flexibilities, by Fourier transform infrared spectroscopy.

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The non-isothermal kinetic analysis of the isotropic-melt to liquid crystalline phase transition of novel liquid crystalline ionogenic copolymers, LCI, the 10-(4-methoxyazobenzene-4'-oxy)decyl methacrylate]-co-2-(acrylamido-2-methyl-1-propanesulfonic acid)s, 10-MeOAzB/AMPS, copolymers, has been performed based on calorimetric experiments at different cooling rates. A classical nonisothermal crystallisation methodology, based on Avrami's equations, was applied and it has shown that the formation of the mesophases from the isotropic state occurred close to the thermodynamic equilibrium and can be described with high accuracy by using different kinetic parameters. The results evidence the presence of several individual processes in the formation of liquid crystalline phases from the melt and a strong dependence of phase transition rates and activation energies with acid contents. In addition, the decrease in the phase transition rate is related to a decrease in orientational entropy and the final inhibition of the liquid crystal behaviour is ascribed to an exponential increase in the activation energy of the phase transition, promoted by strong acid aggregation. An optimum composition of the 10-MeOAzB/AMPS copolymers to achieve the dual characteristics of LCI (ionogenic and liquid crystalline behaviour) requires acid concentrations capable of promoting structure-forming effects on the LC phases and the evolution of phase separated morphologies. I have submitted a manuscript entitled "A kinetic study of the formation of smectic phases in novel liquid crystal ionogens" for consideration for publication in the European PolymerJournal. The manuscript describes the melt-liquid crystal transition of a set of novel liquid crystal side chain copolymers containing sulfonic acid groups having application potential as anisotropic polymer electrolyte membranes. Due to the relevance of the structure-properties relations in these materials, it is important to describe the successive processes involved in the formation of the mesomorphic templates from the isotropic phase. The study of the nonisothermal calorimetric transition carried out in this paper has proved to be useful to describe the forming role of the acid groups on the stabilisation of the liquid crystal phase.The manuscript contains original material which has not been published nor is being considered for publication elsewhere.I look forward to hearing from you in due course. AbstractThe non-isothermal kinetic analysis of the isotropic-melt to liquid crystalline phase transition of novel liquid crystalline ionogenic copolymers, LCI, the 10-(4-methoxyazobenzene-4'-oxy)decyl methacrylate]-co-2-(acrylamido-2-methyl-1-propanesulfonic acid)s, 10-MeOAzB/AMPS, copolymers, has been performed based on calorimetric experiments at different cooling rates. A classical non-isothermal crystallisation methodology, based on Avrami's equations, was applied and it has shown that the formation of the mesophases from the isotropic state occurred close to the thermodynamic...

A homologous series of linear liquid crystal trimers, the 4,4'-bis[v-(4-methoxyazobenzene-4'-yloxy)alkoxy]azobenzenes, has been synthesized and characterized. The transitional properties of the trimers are compared with those of the corresponding series of dimers, the a,v-bis(4-methoxyazobenzene-4'-oxy)alkanes, and monomers, the 4-methoxy-4'-alkoxyazobenzenes. Characteristically pronounced odd-even effects were seen for the transitional properties of both dimers and trimers on varying the spacer lengths. The clearing temperatures of the trimers were higher than those of the corresponding dimers, but as the length of the flexible spacers was increased this difference became rather small. The ratios of T NI , and DS NI /R for monomer:dimer and dimer:trimer are discussed. These are very similar to reported values for similar materials, suggesting that there may be a rather general relationship between the transitional properties of liquid crystal oligomers as the number of mesogenic units is increased.

Lead oxide nanocrystals are synthesised by injecting oxygen gas into an air and moisture free complex of Pb oleylamine and oleic acid in octadecene. Using various characterization methods including fabrication and testing of photovoltaic devices we explore the material properties and photovoltaic application of lead oxide nanocrystal films.

The phase behaviour and mesomorphism of poly(4-(6-propenoyloxyhexyloxy)benzoic acid) (PPOHBA) and 4-pentyloxybenzoic acid (POBA) is studied using variabletemperature Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction. PPHOBA exhibits a smectic C phase and POBA, a nematic phase. The temperature dependence of the Fermi resonance bands associated with the hydroxyl groups and of the carbonyl stretching region in the FTIR spectra indicates that there is a dynamic equilibrium between monomers and open and closed dimers formed by hydrogen bonding between benzoic acid moieties. The nematic phase observed for POBA is linked to the anisotropic cyclic dimer, while an abrupt increase in the concentration of monomer drives isotropisation. In PPOHBA, hydrogen-bonded supramesogens promote smectic behaviour, while hydrogen-bonded crosslinks stabilise the lamellae. The increased viscosity arising from this dynamic crosslinking is offset by the flexibility of the acrylate backbone and alkyl spacers.

The synthesis and characterisation of a novel non-symmetric liquid crystal dimer, 1-[3-O-(D-glucopyranos-3-yl)]-8-[(4-methoxyazobenzene-4'-oxy)]octane is reported. This exhibits glassy behaviour and a highly interdigitated smectic A phase in which the aromatic and alkyl structural fragments overlap. Variable temperature infrared spectroscopy reveals that the strength and extent of hydrogen bonding within the system does not show a marked change at either the glass transition or at the smectic A-isotropic transition. This observation indicates that the smectic A-isotropic transition is driven by changes in the van der Waals interactions between the molecules while hydrogen bonded aggregates persist into the isotropic phase.

The liquid crystalline behaviour of methyl-6-O-(n-dodecanoyl)-α-D-glucopyranoside, 1, has been characterised using X-ray diffraction and variable temperature Fourier transform infrared (FTIR spectroscopy). 1 exhibits a monotropic interdigitated smectic A phase consisting of bilayers in which the alkyl chains are overlapped. The crystal-isotropic transition is accompanied by a pronounced decrease in the strength of the hydrogen bonding network involving the sugar groups resulting in a marked change in the environment of the alkyl chains. The isotropic phase consists of disordered smectic-like domains stabilised via hydrogen bonding between the sugar groups. At the transition to the smectic A phase, a subtle change in hydrogen bonding is observed which is manifested by a change in the temperature dependence of the OH stretching peak position in the FTIR spectrum. On crystallisation, the strong hydrogen bonding network is re-established accompanied by a change in the conformational distribution of the alkyl chains. A model is proposed in which a combination of hydrogen bonding (enthalpic effects) and conformational arrangements (entropic effects) promotes initially the formation of smectic-like domains in the isotropic phase and subsequently stabilises the smectic A phase by inhibiting the microphase separation leading to the crystal phase.