Effect of Confinement on the Structural, Dielectric, and Dynamic Properties of Liquid Crystals in Anopores
Based on data from broadband dielectric spectroscopy (BDS) and a molecular model based on the Landau–de Gennes concept, the effect of confinement on the structural, dielectric, and dynamic properties of 4-n-pentyl-4′-cyanobiphenyl (5CB) in the nematic phase is studied. The dielectric permittivity an...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-03-01
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| Series: | Liquids |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2673-8015/5/1/7 |
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| Summary: | Based on data from broadband dielectric spectroscopy (BDS) and a molecular model based on the Landau–de Gennes concept, the effect of confinement on the structural, dielectric, and dynamic properties of 4-n-pentyl-4′-cyanobiphenyl (5CB) in the nematic phase is studied. The dielectric permittivity and relaxation times were previously obtained by the BDS technique in a wide frequency range (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1</mn><mspace width="3.33333pt"></mspace><mi>MHz</mi><mo>≤</mo><mi mathvariant="normal">f</mi><mo>≤</mo><mn>1</mn><mspace width="3.33333pt"></mspace><mi>GHz</mi></mrow></semantics></math></inline-formula>) in the nematic phase composed of 5CB molecules confined to Anopore membranes with pore sizes of 0.2 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m. The distance-dependent values of the order parameter <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>P</mi><mn>2</mn></msub><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula>, the relaxation time <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>τ</mi><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow><mo>≡</mo><msubsup><mi>τ</mi><mn>00</mn><mn>1</mn></msubsup><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula>, the rotational diffusion coefficient <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>D</mi><mo>⊥</mo></msub><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula>, and both rotational viscosity coefficients <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>γ</mi><mi>i</mi></msub><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></semantics></math></inline-formula> (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>i</mi><mo>=</mo><mn>1</mn><mo>,</mo><mn>2</mn></mrow></semantics></math></inline-formula>) as functions of the distance <i>r</i> away from the bounding surface are calculated by a combination of existing statistical-mechanical approaches and data obtained by the BDS technique. Reasonable agreement between the calculated and experimental values of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>γ</mi><mi>i</mi></msub><mspace width="3.33333pt"></mspace><mrow><mo>(</mo><mi>i</mi><mo>=</mo><mn>1</mn><mo>,</mo><mn>2</mn><mo>)</mo></mrow></mrow></semantics></math></inline-formula> for bulk 5CB is obtained. |
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| ISSN: | 2673-8015 |