C. Casagrande

Flexible polymers in nematic solvents: Phase diagrams in dilute regime

Abstract We present the main types of phase diagrams obtained with flexible polymers in nematic solvents. Data deduced from experimental phase diagrams are compared with two theoretical descriptions.

Viscoelastic properties of side chain mesomorphic polymers in nematic phase: melt and solutions

Abstract We have measured the Franck elastic coefficients and the twist viscosity constant for thermotro-pic side chain mesomorphic polymers, in melt and in solutions. The results are in agreement with a theoretical model based on an anisotropic conformation of the main chain.

Solubilization of a Polymer Chain in a Nematic Phase; Effect on the Twist Viscosity

Abstract We have dissolved short polymer chains (M = 2.103 and 8.103) of poly-ethylen-oxide in the nematic phase of para-azoxy-anisol. On these solutions we measured the twist viscosity γ1. We find an increase of γ1 with the polymer content, correlated to the anisotropy of the polymer chain.

Observation of Anisotropic Droplets in Nematic-Nematic Phase Separation

We report the observation of nonspherical droplets appearing in a nematic-nematic phase separation, and we measure their geometrical anisotropy as a function of the droplets volume and of the temperature. We propose a simple interpretation of this striking anisotropy, in terms of low interfacial tension due to the similarity of coexisting phases in the vicinity of the critical point.

Dynamics of a Fredericks Transition in Side Chain Nematic Polymers : Determination of the Viscoelastic Coefficients K1 and γ1

Abstract We report here measurements of the splay elastic constant, K1, and the twist viscosity coefficient, γ1, of side chain mesomorphic polymers; we compare them so the values obtained for certain low molecular weight compounds, similar to the nematic moiety of the polymers.

Monolayer properties of two isomeric bipolar molecules

Abstract In preliminary two-dimensional polymerization experiments, we have studied the monolayer properties of two isomeric unsaturated diesters. The measurements of isothermal compressibility and surface potential show significant differences in the behavior of the species, as discussed in the framework of phase transition model.

Nematic Solutions of Side Chain Nematic Polymers; A Viscoelastic Study

Abstract We have studied, by analogy with ordinary solutions, the viscoelastic properties of nematic solutions of side chain mesomorphic polymers, for a large domain of concentrations (0 ≤ c ≤ 20% (w/w)). While the splay elastic coefficient K 1 stays constant as c increases to 20%, the twist viscosity coefficient which involves dynamic properties strongly increases and shows a complex behavior. These results are compared to previous results on comparable systems. They are also correlated with an independent and complementary determination of chains sizes and geometry by a SAXS.