Structure Of Liquid Crystal Polymer Research Articles

Machine learning-aided analysis for complex local structure of liquid crystal polymers

Elucidation of mesoscopic structures of molecular systems is of considerable scientific and technological interest for the development and optimization of advanced materials. Molecular dynamics simulations are a promising means of revealing macroscopic physical properties of materials from a microscopic viewpoint, but analysis of the resulting complex mesoscopic structures from microscopic information is a non-trivial and challenging task. In this study, a Machine Learning-aided Local Structure Analyzer (ML-LSA) is developed to classify the complex local mesoscopic structures of molecules that have not only simple atomistic group units but also rigid anisotropic functional groups such as mesogens. The proposed ML-LSA is applied to classifying the local structures of liquid crystal polymer (LCP) systems, which are of considerable scientific and technological interest because of their potential for sensors and soft actuators. A machine learning (ML) model is constructed from small, and thus computationally less costly, monodomain LCP trajectories. The ML model can distinguish nematic- and smectic-like monodomain structures with high accuracy. The ML-LSA is applied to large, complex quenched LCP structures, and the complex local structures are successfully classified as either nematic- or smectic-like. Furthermore, the results of the ML-LSA suggest the best order parameter for distinguishing the two mesogenic structures. Our ML model enables automatic and systematic analysis of the mesogenic structures without prior knowledge, and thus can overcome the difficulty of manually determining the specific order parameter required for the classification of complex structures.

A new high pressure cell with sapphire windows for small-angle neutron scattering

The design and the construction of a cell for the study of the conformation and the structure of liquid crystal polymers under pressure is complex because of the high viscosity of these materials and the use of an external magnetic field to achieve a macroscopic alignment. We have developed a system reaching 1500 bar at 420 K, completely amagnetic, including a small leakproof inner cell sample container with a flexible wall and a larger outer cell resistant to high pressure, with sapphire windows allowing a 8 mm diameter neutron beam aperture, with scattering angles up to 14°. This cell is also equipped with a double sample volume, in order to measure sample volume changes by a differential method.

Thermally Stimulated Processes in a Liquid Crystal Polymer

Measurement of voltage-induced thermal depolarization current and calculation of the rate of depolarization as well as the parameters of drift mobility and conductivity of charge carriers for melt-extruded neat unreinforced grade A950 VECTRA® resin - a wholly aromatic copolyester - strongly suggest that an irreversible minor transition centered around 65°C is the primary thermal process related to molecular realignment. Changes in capacitance values with temperature also show this to be the most active temperature region. A major depolarization peak at 100°C having the characteristics of a Tg cannot be justified as due to glass transition but likely to result from molecular motions involving long range intermolecular order. The interpretation for both transitions can be supported by the mechanical response of this polymer. An important outcome of this work is the assertion that contrary to current thinking, it is the number of charge carriers and not viscosity alone that will have to be considered in future development of fast response liquid crystal displays along with the development of newer liquid crystal polymer structures.

Thermal Analysis, Mechanical and Rheological Behaviour of Melt Manufactured Polyethylene/Liquid Crystal Polymer Blends

Modification of properties of conventional thermoplastics with thermotropic liquid crystal polymers, from one hand, allows decrease their viscosities, substantially facilitating processing conditions, and, from another hand, allows increase their exploitation properties. Orientation of the labile structure of liquid crystal polymer in extrusion or injection moulding causes specific reinforcement (so-called self-reinforcement) to occur in the blends containing liquid crystal polymer. Up to now the effect of self-reinforcement is mostly investigated in the blends, containing considerable amount of liquid crystal polymer. In this research the effect of minor amounts of liquid crystalline co-polyester modifier on the properties of polyethylene is investigated. Various compositions of laboratory synthesized hydroxybenzoic acid /polyethylene terephtalate copolymer containing polyethylene composites have been manufactured by thermoplastic blending. It has been observed that 1) modulus of elasticity, yield strength and ultimate strength increase with raising the content of liquid crystalline modifier; 2) void content in the investigated polyethylene/liquid crystal copolymer composites is not greater that 1 %; 3) addition of liquid crystalline co-polyester modifier improves arrangement of PE crystalline phase.http://dx.doi.org/10.5755/j01.ms.17.2.483