Claude Friedrich

Liquid Crystalline Side Chain Polymers Derived From Poly-acrylate, Poly-methyacrylate and Poly-α-chloroacrylate

Abstract Interest in liquid crystalline side-chain polymers has grown tremendously in recent years because of their theoretical aspects and their potential applications. Over the past few years, a considerable research effort has been made in electro-optic display using nematic or smectic. A mesogenic side-chain polymers. On the other hand, non linear optical effects have been obtained with a nematic side-chain copolymer doped with a molecule exhibiting an extremely large molecular hyperpolarizability β and poled with a D.C. electricfield.

Polymers with terminally cyanobiphenyl-substituted side chains

SummaryTwo acrylate side chain polymers in which the mesogenic moiety is a 4′-cyano-biphenyl-4-yl group have been synthesized and characterized by d.s.c., optical microscopy and X-ray diffraction. If the mesogenic moiety is linked to the polymer backbone by a -O-CO-(CH2)-5 group, the resultant polymer is nematic. For a -O-(CH2)-6 group, the unusual NSANre sequence is observed. X-ray diffraction has shown that the SA phase has a partially bilayer structure : the molecules are arranged in an antiparallel, overlapping interdigitated structure with a layer spacing of about 1.4 times the length of the side chains. Monolayer fluctuations are also observed in this SA phase.

Polymers with mesogenic elements in the main chain: a nematic aromatic copolyester

Abstract Properties of a copolyester based on methylhydroquinone, pyrocatechol and terephthalic acid have been described. Light scattering data for the copolyester in chloroform and dichloroacetic acid are well represented by M w =220 000 while the intrinsic viscosity is 0.22 dl g−1, which implies a compact arrangement of the molecule in dilute solution. Differential scanning calorimetry (d.s.c.) traces show that the copolyester is essentially non-crystalline in character. Polarizing microscopy (texture observations, miscibility tests) provides definite proof as to the nematic structure of the melt. Well aligned samples can be produced either by subjecting nematic melt to a magnetic field (Hc = 0.6 T) or by suitable treatments of the slides between which the melt is observed. The conoscopic interference pattern corresponds to that of a uniaxial system showing an optically positive character. A structural model is proposed to account for the X-ray patterns obtained from oriented samples.

Synthesis and mesomorphic properties of a new thermotropic liquid-crystalline ‘backbone’ copolyester

Details of the thermal behaviour of the following liquid-crystalline ‘backbone’ copolyester are reported: — [OCC6O]0.6+[OOCC6H4OCH2CH2OC2H4COOCH2CH2]0.4? Between 218° and 337°C, observations using a polarizing microscope indicate the formation of a birefringent melt that exhibits a Schlieren texture. From the observation of disclinations of strength ± 12, the mesophase can be identified as a nematic phase. The isobaric phase diagram of mixtures of copolyester and N,N′-di-(ρ-methoxy benzylidene)-α,α′-bi-ρ-toluidine and X-ray diffraction patterns provide definite proof as to the nematic structure of the birefringent melt. Addition of a chiral compound to the copolyester in the nematic state causes the formation of the typical textures of cholesterics. The temperature dependence of the order parameter has been determined from FTi.r. polarized spectra. At high temperature S is found to be 0.3. Such a result confirms the recent theory of Ronca and Yoon: the isotropic-nematic transition of semiflexible polymers does not entail a very high degree of order in the resultant nematic phase.

Thermotropic liquid crystalline polyesters with terphenyl moieties and flexible «ether» spacers in the main chain

Abstract Polyesters with the general formula: (n=1 (TO 5), 3 (TO 11), 9 (TO 29)) were characterized by differential scanning calorimetry, optical microscopy, miscibility tests and X-ray investigations. In polyesters TO 5 and TO 11 a smectic phase type C occurs. X-ray studies of oriented samples have suggested that the smectic C configuration is azimuthally disordered with the layers orientationally ordered. By contrast, above its melting point the polyester TO 29 shows distinct phases of liquid crystal and isotropic liquid. This is probably due to the polydispersity of the low molecular weight fraction of PEO used in preparing this polyester. A structural model is proposed to illustrate how the polyesters under investigation can adopt organizations compatible with all data known so far.

Liquid-crystalline side-chain polymers: 2. Poly(allyl carbonates) and poly(vinyl carbonates)

The free-radical polymerization of two families of nematic vinyl and allyl carbonates has been investigated starting from both the isotropic and nematic phases of the monomers. The thermal properties of the resulting polymers were examined by polarizing microscopy, differential scanning calorimetry and X-ray diffraction, and their microstructure was analysed by 13C nuclear magnetic resonance. A change in the stereoregularity of the poly(vinyl carbonates) was observed when the polymers were prepared from the nematic phase of the monomers compared to the isotropic phase.

Etude Polarographique des Solutions Aqueuses D’ Aquopentacyanoferrate(II)

La complexite des solutions aqueuses d’ aquopentacyanoferrates se manifest par un ensemble de proprietes singulieres, en particulier des proprietes electrochimiques, ayant suscite des interpretations diverses. C’ est ainsi que les anomalies de conductivite ont conduit a invoquer l’existence de deux eqquilibreformes en acidobasique (1) et l’allure inusuelle des courbes de potentiels d’ oxydoreduction celle d’ associations plurimoleculaires (2, 3). L’ etude cinetique de la reaction du nitrosobenzene a permis de reconnaitre la presence de deux types au moins de constituants, dont les relations seraient celles de monomere a polymere, comme aussi de les doser (4); il a ete reconnu effectivement que l’un est susceptible de dialyser et l’autre pas a travers une membrane de cellophane disposee entre la solution d’ aquopentacyanoferrate(II) et de la methylethylcetone saturee d’ eau (5). Nous nous sommes propose de ettuderechercher quelle contribution pourrait apporter une polarographique.