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 language | English |
|---|---|
| Pages (from-to) | 718-725 |
| Number of pages | 8 |
| Journal | Advanced Functional Materials |
| Volume | 13 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - 2003 Sep 1 |
| Externally published | Yes |
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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 journal › Article
}
TY - JOUR
T1 - Assembly of photopolymerizable discotic molecules on an aligned polyimide layer surface to form a negative retardation film with an oblique optical axis
AU - Ge, Jason J.
AU - Hong, Seok Cheol
AU - Tang, Benjamin Y.
AU - Li, Christopher Y.
AU - Zhang, Dong
AU - Bai, Feng
AU - Mansdorf, Bart
AU - Harris, Frank W.
AU - Yang, Denke
AU - Shen, Yuen Ron
AU - Cheng, Stephen Z D
PY - 2003/9/1
Y1 - 2003/9/1
N2 - 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.
AB - 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.
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U2 - 10.1002/adfm.200304365
DO - 10.1002/adfm.200304365
M3 - Article
AN - SCOPUS:0141724913
VL - 13
SP - 718
EP - 725
JO - Advanced Functional Materials
JF - Advanced Functional Materials
SN - 1616-301X
IS - 9
ER -