Effect of Position and Structure of the Terminal Moieties in the Side Group on the Liquid Crystal Alignment Behavior of Polystyrene Derivatives.

Hyo Kang,Kyutae Seo,DaEun Yang

doi:10.3390/polym13162822

Abstract

We synthesized a series of polystyrene derivatives containing various side groups, such as the 4-(tert-butyl)-phenoxymethyl, 3-(tert-butyl)-phenoxymethyl, 2-(tert-butyl)-phenoxymethyl, 4-cumyl-phenoxymethyl, and 4-trityl-phenoxymethyl groups, through a polymer modification reaction to examine the liquid crystal (LC) alignment of these derivatives. In general, the vertical LC alignment on polymer films can be affected by the position and structure of the terminal moiety of the polymer side group. For example, the LC cells fabricated with 4-(tert-butyl)-phenoxymethyl-substituted polystyrene having a tert-butyl moiety as a para-type attachment to the phenoxy groups of the polystyrene derivatives exhibited vertical LC alignment, whereas the LC cells prepared from 3-(tert-butyl)- and 2-(tert-butyl)-phenoxymethyl-substituted polystyrene films exhibited planar LC alignment. In addition, the LC cells fabricated from 4-cumyl- and 4-trityl-phenoxymethyl-substituted polystyrene films with additional phenyl rings in the side groups exhibited planar LC alignment, in contrast to the LC alignment of the (tert-butyl)-phenoxymethyl-substituted polystyrene series. The vertical LC orientation was well correlated with the surface energy of these polymer films. For example, vertical LC orientation, which mainly originates due to the nonpolar tertiary carbon moiety having bulky groups, was observed when the surface energy of the polymer was lower than 36.6 mJ/m2.

Highlights

Liquid crystals (LCs), which consist of elongated organic molecules with an uneven charge distribution along their dipoles, are materials with properties between those of ordinary liquids and three-dimensional solids [1,2,3]
LCs have been studied in elementary research and for the development of commercial applications owing to their exceptional anisotropic physicochemical characteristics
4-Trityl-phenoxymethyl-substituted polystyrene (PTRI) was synthesized using a procedure similar to that used for preparing P4TB, except that 4-tritylphenol (0.99 g, 2.95 mmol, 150 mol% relative to PCMS) was used instead of 4-(tert-butyl)phenol

Summary

Introduction

Liquid crystals (LCs), which consist of elongated organic molecules with an uneven charge distribution along their dipoles, are materials with properties between those of ordinary liquids and three-dimensional solids [1,2,3]. Polystyrene derivatives with long alkyl or fluoroalkyl groups have been developed for application in noncontact methods to achieve a vertical orientation of LC molecules on substrates This is because the long alkyl or fluoroalkyl groups on the polystyrene layer result in low surface energy owing to the steric effects of these groups on the polymer film surface. The vertical orientation of LC molecules in LC cells fabricated with PS derivatives substituted with natural extracts, such as capsaicin [47], eugenol [48], vanillin [49], oryzanol [50], and tocopherol [51], was observed when the substituent ratio was greater than 60 mol% This is due to the long alkyl groups of the natural extracts, which are related to the low surface energy owing to the steric effect of the alkyl groups on the polymer film surface.

Materials

Film Preparation and LC Cell Assembly

Instrumentation

Results and Discussion

The was vertical

Conclusions