Abstract
A series of polystyrene derivatives containing precursors of liquid crystal (LC) molecules, phenylphenoxymethyl-substituted polystyrene (PPHE#; # = 5, 15, 25, 50, 75, and 100)—where # is the molar content of 4-phenylphenol using polymer modification reactions—were prepared in order to examine the effect of the polymer film, which possess similar LC molecular structure on the LC alignment properties. It was found that the Tg values of the PPHE# were higher than 100 °C due to their aromatic structure in the biphenyl-based PHE moiety. The LC cells fabricated with PPHE5 and PPHE15 films exhibited planar LC alignment. Conversely, LC molecules showed a vertical alignment in LC cells made using the polymer films with phenylphenoxymethyl side groups in the range of 25–100 mol %. The polar surface energies on the PPHE# films can be associated with the vertical LC alignment on the PPHE# films. For example, vertical LC alignment was exhibited when the polar surface energy of the polymer films was less than approximately 4.2 mJ/m2. Aligning stability was observed at 200 °C and UV irradiation of 20 J/cm2 for LC cells made using the PPHE100 film. Therefore, it was found that biphenyl, one of the LC precursors, modified polystyrene derivatives and can produce a next-generation vertical LC alignment system.
Highlights
Academic Editors: Patrick Ilg andThe physicochemical properties—such as thermal conductivity [1–4], mechanical properties [5–7], and wettability [8,9]—of anisotropic molecules are influenced by their molecular alignments
A copolymer series of polystyrene substituted with phenylphenoxymethyl (PPHE#)
SyntheA copolymer series moiety, of polystyrene substituted with phenylphenoxymethyl sized in order evaluate moiety, the liquid crystal (LC) alignment behavior of the polymer films
Summary
The physicochemical properties—such as thermal conductivity [1–4], mechanical properties [5–7], and wettability [8,9]—of anisotropic molecules are influenced by their molecular alignments. LC molecules vertically onto substrates using non-contact methods, because the phenolic compounds can be modified with surfaces of substrates including polymers and metals by various reactions [47–50]. The vertical alignment of LC molecules in LC cells made from PS derivatives modified with biorenewable resources, including phenolic compounds—such as capsaicin, eugenol, and vanillin—was observed This is due to the bulky groups of the biorenewable resources which are closely related to low surface energy value owing to the steric effect of bulky groups onto the polymer surface [51–57]. LC alignment behaviors could be studied very systematically Surface characterization, such as surface energy measurement, was carried out in order to investigate the effect of the wettability on the LC alignment properties of the polymer film. The synthesis and characterization of these polymer series and the optical properties of the fabricated LC cells made from polymer films were included
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