S. B. Clough

Synthesis and properties of some polyesters with mesogenic groups and flexible spacers in the main chain

Abstract Polymers containing, in the main chain, various mesogenic moieties separated by flexible spacers have been prepared by condensation of the corresponding diphenol or diol with an aliphatic diacid chloride. The polymers have been characterized by X-ray, d.s.c. and polarizing microscopy. The diacids used were sebacic (SEB), succinic (SUC) and 3-methyladipic (MAA). The biphenols were 4-hydroxyl- N -benzylidene-4′-hydroxyaniline(1), 4.4′-biphenol(2), 4,4′-bis (2-hydroxyethoxy)-biphenyl(5) and 3,3′-dimethyl-4,4′-di(2-hydroxyethoxy)-stilbene(7). The polymers SEB-1 and SEB-2 were classified as giving thermotropic lamellar mesophases; SEB-5, SEB-7 and SUC-5 as potentially nematic; MAA-2 and SUC-2 gave crystalline polymers.

Diacetylenic Liquid Crystalline Polymers II: Derivatives of 10,12-Docosadiyne-1,22-Dioic Acid

Abstract Polymers of 10,12-docosadiyne-1,22-dioic acid with different mesogenic groups have been prepared. The mesogenic groups were diphenyl (Polymer I); p-diphenylazoxy (Polymer 11); 2,2′-dimethyldiphenylazoxy (Polymer III); 2-methyldiphenylazomethine (Polymer IV) and α-methylstilbene (Polymer V). All polymers crystallized extensively at room temperature, but only polymers I and V have displayed an enantiotropic smectic mesophase. The X-ray diffractograms were consistent with a smectic H mesophase for both polymers. Polymers I and V differed also from polymers 11-IV by enhanced reactivity of the diacetylenic moiety. A model for chain packing consistent with the X-ray diffraction pattern of the crystalline and the smectic phase is proposed.

Molecular Mass and Structure Dependence of Liquid Crystalline Properties for a Homologous Series of Polyesters

Abstract Mesomorphic properties of higher homologues of flexible main chain thermotropic polyesters based on regularly alternating p-dioxy,2,2′dimethylazoxybenzene mesogen and (α,αω)-alkanedicarboxylic acid were investigated. Attention was given to changes from cybotactic nematic to smectic C (Nc—Sc) mesophases. On the basis of SAX data, rheology and miscibility diagrams with low M compounds displaying both a Sc and Nc mesophase it was shown that the polyester with n=18 and M > 3,000 displays a Sc monotropic mesophase. The data suggest that while polyesters of odd spacer parity in the nematic quiescent state do not display any tendency toward formation of layered order, polyesters with n even exhibit a pronounced tendency toward the formation of layered order, This tendency increasing with n and M is favored by a decrease of temperature. It may be argued that the observed passage Nc—Sc is continuous. The formation of layered (Nc) order was also observed for large n and M for a spacer of odd parity but onl...

Dynamics Simulation of Langmuir-Blodgett Films

Abstract Langmuir-Blodgett monolayers are formed when amphiphilic molecules dissolved in volatile solvent are deposited on water surface followed by compression. During the compression, the randomly oriented molecules reorient themselves with the hydrophilic head groups on the water surface and the hydrophobic tail standing away from the water surface. The monolayer can then be transferred onto a solid substrate. LB-film multilayer can be made when monolayers are repeat transferred onto the same solid substrate. By altering the amphiphilic molecules chemical structure and the number and type of monolayers in an LB-film multilayer, we can tailor the thickness, physical and chemical properties of the films. It is also possible to initialize polymerization on certain function group in a monolayer to enhance the mechanical properties or create other unique electro-optical properties. These organic ultra-thin films with highly ordered layer structure, have shown a wide range of potential applications in bioch...

Thermotropic Polymeric Liquid Crystals: Polymers with Mesogenic Elements and Flexible Spacers in the Main Chain

It is known since the work of Roviello and Sirigu (1) that polymers with mesogenic moieties and flexible sequences of methylene groups in the main chain display thermotropic liquid crystalline behavior. It was assumed that nematic phases are strongly favored. More recently we have studied poly (ester) derivatives of 4,4′-dihydroxyhyphenyl and 4,4′-dihydroxystilbene, condensed with sebacic acid and shown that smectic mesophases appear in these systems (2).