Molecular Crystals and Liquid Crystals Incorporating Nonlinear Optics, 1988
We show that the birefringence of the lamellar phase of the C12E6-H2O system decreases abruptly a... more We show that the birefringence of the lamellar phase of the C12E6-H2O system decreases abruptly as the temperature increases towards the lamellar-isotropic transition. As the order parameter does not show such behaviour, but decreases regularly, we attribute this phenomenon to disorienting defects whose concentration increases with temperature and diverges when approaching the phase transition, as observed previously by electron microscopy.
ABSTRACT I measure the Leslie thermomechnical coefficient ν in diluted cholesteric liquid crystal... more ABSTRACT I measure the Leslie thermomechnical coefficient ν in diluted cholesteric liquid crystals. The chiral molecules are R811 and cholesteryl chloride (CC) and the host nematic liquid crystals are 7CB and MBBA. I show that ν is proportional to the concentration of chiral molecules C when . This allows me to define the Leslie thermomechanical power as by analogy with the helical twisting power, where q denotes the equilibrium twist. I show that the LTP (dynamic in nature) and the HTP (static in nature) are independent in sign and magnitude. In addition, the same chiral molecule can rotate clockwise or counterclockwise depending on the host nematic liquid crystal used.
In ordinary liquids the size of a meniscus and its shape is set by a competition between surface ... more In ordinary liquids the size of a meniscus and its shape is set by a competition between surface tension and gravity. The thermodynamical process of its creation can be reversible. On the contrary, in smectic liquid crystals the formation of the meniscus is always an irreversible thermodynamic process since it involves the creation of dislocations (therefore it involves friction). Also
A lamellar phase confined between parallel walls changes its structure when compared with the bul... more A lamellar phase confined between parallel walls changes its structure when compared with the bulk system. The system is studied here in the Monte Carlo simulations of the Landau–Ginzburg model of a ternary mixture of oil, water, and surfactant. In the case of strongly hydrophilic boundary conditions at the walls, we observe strong topological fluctuations in the form of passages. As we change the distance between the walls we observe the formation of two surfactant layers, then the microemulsion between two layers, and finally four surfactant layers. The transition is marked by the peaks in the average Euler characteristic and in its variance. In the case of strongly hydrophilic boundary conditions at one wall and strongly hydrophobic boundary condition at the other, we observe under dilation a permanent deformation of layers in the middle of the system. In the case of weakly hydrophilic boundary conditions, the system exhibits strong topological fluctuations (passages and droplets...
Molecular Crystals and Liquid Crystals Incorporating Nonlinear Optics, 1988
We show that the birefringence of the lamellar phase of the C12E6-H2O system decreases abruptly a... more We show that the birefringence of the lamellar phase of the C12E6-H2O system decreases abruptly as the temperature increases towards the lamellar-isotropic transition. As the order parameter does not show such behaviour, but decreases regularly, we attribute this phenomenon to disorienting defects whose concentration increases with temperature and diverges when approaching the phase transition, as observed previously by electron microscopy.
ABSTRACT I measure the Leslie thermomechnical coefficient ν in diluted cholesteric liquid crystal... more ABSTRACT I measure the Leslie thermomechnical coefficient ν in diluted cholesteric liquid crystals. The chiral molecules are R811 and cholesteryl chloride (CC) and the host nematic liquid crystals are 7CB and MBBA. I show that ν is proportional to the concentration of chiral molecules C when . This allows me to define the Leslie thermomechanical power as by analogy with the helical twisting power, where q denotes the equilibrium twist. I show that the LTP (dynamic in nature) and the HTP (static in nature) are independent in sign and magnitude. In addition, the same chiral molecule can rotate clockwise or counterclockwise depending on the host nematic liquid crystal used.
In ordinary liquids the size of a meniscus and its shape is set by a competition between surface ... more In ordinary liquids the size of a meniscus and its shape is set by a competition between surface tension and gravity. The thermodynamical process of its creation can be reversible. On the contrary, in smectic liquid crystals the formation of the meniscus is always an irreversible thermodynamic process since it involves the creation of dislocations (therefore it involves friction). Also
A lamellar phase confined between parallel walls changes its structure when compared with the bul... more A lamellar phase confined between parallel walls changes its structure when compared with the bulk system. The system is studied here in the Monte Carlo simulations of the Landau–Ginzburg model of a ternary mixture of oil, water, and surfactant. In the case of strongly hydrophilic boundary conditions at the walls, we observe strong topological fluctuations in the form of passages. As we change the distance between the walls we observe the formation of two surfactant layers, then the microemulsion between two layers, and finally four surfactant layers. The transition is marked by the peaks in the average Euler characteristic and in its variance. In the case of strongly hydrophilic boundary conditions at one wall and strongly hydrophobic boundary condition at the other, we observe under dilation a permanent deformation of layers in the middle of the system. In the case of weakly hydrophilic boundary conditions, the system exhibits strong topological fluctuations (passages and droplets...
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