Effect of 1-ethynyl-4-(trifluoromethyl) benzene on polymer network liquid crystal

ABSTRACT

The polymer network liquid crystals (PNLCs) device has the advantages of large manufacturing area, high transmittance, but still has the disadvantages of high driving voltage and large hysteresis. In this paper, 1-ethynyl-4-(trifluoromethyl) benzene (ETB) was used in polymer network liquid crystal system to reduce the threshold and saturation voltage and hysteresis. The functional group of ETB is an alkynyl group, which can be regarded as polymer monomer or diluent because of its polymerisation less than the alkenyl group. When the whole weight content of polymer is 5 wt% and the 1 wt% ETB as a monomer, the operating voltage of PNLCs is reduced by 63.1%, and the hysteresis is reduced to 0.18 V. As a diluent, when the weight content of 1,4-Bis-[4-(3-acryloyloxypropyloxy)benzoyloxy]-2-methylbenzene (RM257) and ETB is 5% and 1%, the operating voltage of the polymer network liquid crystal is reduced by 51.5%, and the hysteresis is reduced to 0.38 V. From these two experiments, a small amount of ETB material doping can significantly reduce the operating voltage and hysteresis effect of PNLCs devices. Moreover, the equivalent rotational viscosity of the polymer network liquid crystals with suitable content of ETB as diluent can be reduced to be similar to that of the pure liquid crystal.

Graphical abstract

KEYWORDS:

• Polymer-network liquid crystals
• threshold voltage
• hysteresis
• decay time
• diluent

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [61475042];National Key R&D Program of China [2018YFB0703701].