Abstract
We investigated the liquid crystal (LC) alignment behaviors of butyl hydroxybenzoate-substituted polystyrene (PBHB#; # = 20, 40, 60, 80, and 100, where # indicates the molar fraction of butyl hydroxybenzoate in the side chain), methyl hydroxybenzoate-substituted polystyrene (PMHB100), and ethyl hydroxybenzoate-substituted polystyrene (PEHB100). Generally, LC cells made employing polymer films having longer alkyl groups in the side chain show vertical LC alignment. For instance, a LC cell fabricated with the PMHB100 film showed random planar LC alignment, while the LC cells made from the PEHB100 and PBHB100 films exhibited vertical LC alignment. Moreover, LC cells prepared from a polymer film having a higher molar content of butyl hydroxybenzoate in the side chain exhibited vertical LC alignment. The observed vertical LC alignment behaviors are closely related to the surface energy of these polymer films. For instance, vertical LC alignment was observed when the surface energy of the polymer film was less than ~43.86 mJ/m2, which could result from the nonpolar alkyl groups of the alkyl hydroxybenzoate moiety. The LC cell prepared from PBHB100 as the LC alignment layer showed good electro-optical characteristics such as voltage holding ratio, residual DC voltage, and alignment stability at 200 °C.
Highlights
Liquid crystals (LCs) are extensively investigated because they have a unique property of showing an intermediate phase with solid- and liquid-like properties [1]
The transmittance of the glass slides coated with PBHB#, PMHB100, and PEHB100 films was found to be in the range of 98.4–99.6% at 550 nm; this transmittance is higher than that (86.3%) of the commonly used polyimide (PI) film, which has some problems of connatural yellowish coloration associated with the conjugation of di-imide fragments in the LC alignment layer [51,52,53]
Based on the results obtained for the LC alignment behavior, we found a universal trend that the polymers longer alkyl groups higher molar contents of the alkyl hydroxybenzoate
Summary
Liquid crystals (LCs) are extensively investigated because they have a unique property of showing an intermediate phase with solid- and liquid-like properties [1]. LC cells prepared employing a nematic LC and rubbed polymer films of n-alkylsulfonylmethyl- and n-alkylthiomethyl-substituted polystyrenes consisting of alkyl groups with more than eight carbons showed vertical LC alignment behaviors [37]. LC cells prepared from 4-alkylphenoxymethyl-substituted polystyrenes showed vertical LC alignment behaviors even at a very high rubbing density of 250, irrespective of the length of the alkyl side groups [38]. We synthesized alkyl hydroxybenzoate-substituted polystyrenes (PBHB# (# = 20, 40, 60, 80, and 100, where # means the molar fraction of butyl hydroxybenzoate in the side chain), PMHB100, and PEHB100) to obtain a vertical alignment of LCs and to research the effect of the length and molar contents of the alkyl hydroxybenzoate side groups on the LC alignment behavior for the first time. We studied the optical and electrical properties of the LC cells prepared employing the polymer films
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
