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Updated: Jul 24, 2026
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Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets
Published on: May 15, 2017
Alignment of liquid crystals on a photosensitive substrate studied by surface optical second-harmonic generation
Drevensek Olenik I1, Kim, Rastegar
1Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI 1000, Ljubljana, SloveniaJ. Stefan' Institute, Jamova 39, SI 1001 Ljubljana, Slovenia.
Summary
The study reveals that liquid crystal film adsorption on modified polymers slows with increased polymer changes. Surface alignment of 4(
Area of Science:
- Materials Science
- Surface Science
- Polymer Chemistry
Background:
- Investigating liquid crystal (LC) alignment on polymer substrates is crucial for display technologies.
- Poly(vinyl-cinnamate) (PVCN) is a photosensitive polymer used for surface alignment.
- Understanding adsorption kinetics and orientational ordering is key to controlling LC film properties.
Purpose of the Study:
- To investigate the adsorption kinetics and orientational ordering of 4(')-n-octyl-4-cyanobiphenyl (8CB) liquid crystal films on poly(vinyl-cinnamate) (PVCN) substrates.
- To correlate the photochemical modification of PVCN substrates with the adsorption and alignment of 8CB films.
- To elucidate the factors influencing surface anchoring of LCs on PVCN alignment layers.
Main Methods:
- Surface optical second-harmonic generation (SHG) was employed to probe the adsorption and orientation.
- 8CB liquid crystal films were evaporated onto PVCN substrates with varying degrees of photochemical modification.
- Substrates were prepared with unidirectional photopolymerization to induce alignment.
Main Results:
- The adsorption rate of the initial 8CB monolayer decreased as the photochemical modification of PVCN increased.
- The in-plane orientational anisotropy of 8CB films on photopolymerized PVCN was significantly lower than the substrate's intrinsic anisotropy.
- This discrepancy suggests weak surface anchoring of liquid crystals on PVCN alignment layers.
Conclusions:
- Photochemical modification of PVCN influences the adsorption kinetics of 8CB liquid crystal films.
- The orientational ordering of 8CB films is limited by the substrate's alignment capabilities, indicating weak surface anchoring.
- Findings provide insights into optimizing PVCN-based alignment layers for liquid crystal applications.
