Inducement of homogeneous liquid crystal alignment on surface-reformed polyurethane films via manipulation of ion-beam irradiation incidence angle

Hae Chang Jeong, Ju Hwan Lee, Dong Hyun Kim, Dong Wook Lee, Byeong Yun Oh, Jeong Min Han, Dae Shik Seo

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

We investigated the induced uniform alignment of liquid crystals (LCs) on a polyurethane (PU) ion-beam (IB) irradiated at a certain incidence angle. Polarized optical microscopy (POM) and the crystal rotation method were used to evaluate the LC alignment state. On PU films IB-irradiated with incidence angles of 60° or less, the LC cells exhibit a clear and uniform alignment. At an incidence angle of 75°, light scattering was observed via POM, indicating the randomly aligned state of the LC cells. Moreover, the calculated pretilt angles for LC cells on IB-irradiated PU at incidence angles of 15°, 30°, 45°, and 60° were 0.05°, 0.05°, 0.20°, and 0.18°, respectively. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to confirm the effect of varying the IB irradiation incidence angle. The PU surface irradiated by IB was modified differently as the incidence angle changed. IB irradiation at low incidence angles broke C–C, C–O/C–N, and N–C(O)–O bonds and caused C=O bond formation by the dissociation of the N–C(O)–O bonds. The van der Waals interactions between the PU and LC matched the LC molecular interactions and the anisotropic characteristics could be maintained, thereby achieving a stable homogeneous LC alignment.

Original languageEnglish
Pages (from-to)325-330
Number of pages6
JournalSoft Materials
Volume15
Issue number4
DOIs
Publication statusPublished - 2017 Oct 2

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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