Assembly of photopolymerizable discotic molecules on an aligned polyimide layer surface to form a negative retardation film with an oblique optical axis

Jason J. Ge, Seok Cheol Hong, Benjamin Y. Tang, Christopher Y. Li, Dong Zhang, Feng Bai, Bart Mansdorf, Frank W. Harris, Denke Yang, Yuen Ron Shen, Stephen Z D Cheng

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Ultraviolet (UV) polymerizable discotic liquid-crystalline (DLC) molecules (2,3,6,7,10,ll-hexakis(4′-acryloy-m-alkyloxyben- zoyoxy)triphenylene [HAHBT-m, where m was the number of methylene units, and here m = 6 (HAHBT-6)]) were assembled to form a negative retardation film with an oblique optical axis on a specifically designed rubbing-aligned polyimide layer surface [6FDA-11CBBP (where 11 is the number of methylene units in the side chains)]. The side chains of this polyimide were terminated by cyanobiphenyl groups. Surface-enhanced Raman scattering (SERS) and optical second harmonic generation results showed that rubbing caused a surface structural re-arrangement in the alignment layer resulting in a negative pre-tilt angle (θ s) of -8.5° (which was in the direction opposite to the rubbing direction). The molecular topology at the rubbed surface was governed by a stable fold-like bent structure of the cyanobiphenyl side chains, in which the CN groups preferentially pointed down towards the surface. When the DLC molecules were deposited onto the alignment surface and polymerized via UV irradiation to generate a new optical film, an oblique optical axis with an average tilt angle of -18.6° with respect to the film normal was detected using ellipsometric measurements. This tilted optical axis was developed by the DLC molecules being wedged on top of the cyanobiphenyl groups when in the bent conformation. Furthermore, the tilt angle difference between the θ sat the alignment surface and at the air interface of the DLC molecules was attributed to a splay deformation of the DLC molecules along the film surface normal. Optical modeling has also confirmed our experimental observations.

Original languageEnglish
Pages (from-to)718-725
Number of pages8
JournalAdvanced Functional Materials
Volume13
Issue number9
DOIs
Publication statusPublished - 2003 Sep 1
Externally publishedYes

Fingerprint

polyimides
Polyimides
surface layers
assembly
Molecules
molecules
Crystalline materials
liquids
Liquids
alignment
methylene
Optical films
Harmonic generation
harmonic generations
topology
Conformations
Raman scattering
Raman spectra
Topology
Irradiation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Materials Science(all)
  • Condensed Matter Physics
  • Physics and Astronomy (miscellaneous)

Cite this

Assembly of photopolymerizable discotic molecules on an aligned polyimide layer surface to form a negative retardation film with an oblique optical axis. / Ge, Jason J.; Hong, Seok Cheol; Tang, Benjamin Y.; Li, Christopher Y.; Zhang, Dong; Bai, Feng; Mansdorf, Bart; Harris, Frank W.; Yang, Denke; Shen, Yuen Ron; Cheng, Stephen Z D.

In: Advanced Functional Materials, Vol. 13, No. 9, 01.09.2003, p. 718-725.

Research output: Contribution to journalArticle

Ge, Jason J. ; Hong, Seok Cheol ; Tang, Benjamin Y. ; Li, Christopher Y. ; Zhang, Dong ; Bai, Feng ; Mansdorf, Bart ; Harris, Frank W. ; Yang, Denke ; Shen, Yuen Ron ; Cheng, Stephen Z D. / Assembly of photopolymerizable discotic molecules on an aligned polyimide layer surface to form a negative retardation film with an oblique optical axis. In: Advanced Functional Materials. 2003 ; Vol. 13, No. 9. pp. 718-725.
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AU - Bai, Feng

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AU - Shen, Yuen Ron

AU - Cheng, Stephen Z D

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