A parallel high-throughput approach to liquid crystal screening

Abstract

A technique has been developed for the high-throughput ͑HT͒ parallel screening of liquid crystal ͑LC͒ phase transitions, using optical anisotropic effects observed only in the LC state to allow the determination of melting and clearing points. A camera was used to monitor optical changes observed in arrays of LC samples upon heating, when illuminated with plane polarized light and viewed through a second polarizer aligned perpendicular to the plane of polarized light. Data was processed using Image Pro Plus, extracting values for the melting point and clearing point of each sample in the array. When compared with literature and conventional differential scanning calorimetry the new technique was found to be in excellent agreement, establishing the technique as a viable HT alternative. The method was used to analyze a 75 formulation library prepared using liquid handling for HT clearing point determination, showing the scope and power of the technique in the analysis of larger libraries.

Liquid Crystal Libraries—Ink‐jet Formulation and High‐Throughput Analysis

“…HT screening and data processing were achieved using the published equipment and methods in described elsewhere [20], with the exception of a modification to allow cooling. The addition of channels in the heating block allowed a flow of cooled N 2 gas, hence providing the capability for subambient temperature analysis.…”

“…Solvents that solubilized the LCs were then printed onto a glass substrate in a 5 × 1 matrix printing 1 to 100 drops in 20 drop increments. These spots were assessed for quality before placing the substrate in an oven for 3 min at 80°C, cooling, and then analyzing [20] for melting point (T m ) and clearing point (T cp The results in Figure 2 show that the location of the eutectic temperature (highlighted) does indeed lie in a minimum, as predicted by theoretical calculations. In the experimental results the 40:20:40 formulation had a melting point of 34.0°C.…”

“…In the area of LCs the bottleneck of such an approach was the unavailability of suitable HT analytical techniques. [19] However, this has partially been solved by the development of an optical birefringence method for HT detection of LC phase transitions [20] that constitutes a simple, but important first screen allowing areas of particular interest to be identified and then exemplified using more complex methods such as dielectric anisotropy, optical anisotropy, magnetic susceptibility and viscosity analysis. [21,22] In this Communication we describe the design, optimization, and formulation of a 231 member tertiary library of liquid crystals by using ink-jet printing, followed by screening for phase transitions, with only a few milligrams of material needed for complete library analysis.…”

“…A voltage of 104 V, a pulse width of 29 ms, and a drop frequency of 60 Hz were used to print a total of 23 100 drops of the three inks onto 231 positions. Screening of the library was then carried out using the HT phase transition equipment [20] using a heat-cool-heat temperature ramp from -50°C to 100°C. The optical transitions of each sample spot were then analyzed to provide the temperature of the phase transitions (Fig.…”

High-throughput viscosity determinations

“…[1][2][3] This ability, however, then brings to the fore the requirement to rapidly characterize the formulations that are generated, with the need to determine a range of physical parameters, which includes viscosity and density. [1][2][3] This ability, however, then brings to the fore the requirement to rapidly characterize the formulations that are generated, with the need to determine a range of physical parameters, which includes viscosity and density.…”