‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material
Results of dielectric studies in the nematic and isotropic liquid phases of pentylcyanobiphenyl (5CB), a model rod-like liquid crystalline material, are shown. They are based on the discussion of the evolution of dielectric constant (<inline-formula> <math display="inline"> <...
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| Format: | Article |
| Language: | English |
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MDPI AG
2020-04-01
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| Series: | Crystals |
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| Online Access: | https://www.mdpi.com/2073-4352/10/4/297 |
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| author | Aleksandra Drozd-Rzoska |
| author_facet | Aleksandra Drozd-Rzoska |
| author_sort | Aleksandra Drozd-Rzoska |
| collection | DOAJ |
| description | Results of dielectric studies in the nematic and isotropic liquid phases of pentylcyanobiphenyl (5CB), a model rod-like liquid crystalline material, are shown. They are based on the discussion of the evolution of dielectric constant (<inline-formula> <math display="inline"> <semantics> <mi>ε</mi> </semantics> </math> </inline-formula>), its changes under the strong electric field (nonlinear dielectric effect, NDE), and finally, the primary relaxation time. It is shown that changes in <inline-formula> <math display="inline"> <semantics> <mrow> <mi>ε</mi> <mfenced> <mi>T</mi> </mfenced> </mrow> </semantics> </math> </inline-formula> and NDE are entirely dominated by the impact of pretransitional fluctuations (pre-nematic and pre-isotropic, respectively) which are associated with the weakly discontinuous character of the isotropic–nematic phase transition. This influence also extends for the low-frequency, ionic species dominated, region. Notable, that the derivative-based and distortions sensitive analysis revealed the tricritical nature of the I-N transition. Although the glass transition in 5CB occurs in the deeply supercooled state at <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi>g</mi> </msub> <mo>≈</mo> <mo>−</mo> <mn>68</mn> <mtext> </mtext> <mo>°</mo> <mi mathvariant="normal">C</mi> </mrow> </semantics> </math> </inline-formula>, the dynamics (changes of the primary relaxation time) follow a previtreous pattern both in the isotropic and in the nematic phase. Finally, the discussion of the ’<i>molecular</i>’ vs. ‘<i>quasi-critical</i>’ characterizations of the isotropic and nematic phases is presented. It shows the evident prevalence of the ‘quasi-critical-picture’, which offers the consistent temperature parameterization in the total tested temperature range. |
| first_indexed | 2024-03-10T20:30:28Z |
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| institution | Directory Open Access Journal |
| issn | 2073-4352 |
| language | English |
| last_indexed | 2024-03-10T20:30:28Z |
| publishDate | 2020-04-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Crystals |
| spelling | doaj.art-e5ebcb93fc8f44cc9e2ce074467662bd2023-11-19T21:28:06ZengMDPI AGCrystals2073-43522020-04-0110429710.3390/cryst10040297‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline MaterialAleksandra Drozd-Rzoska0Institute of High Pressure Physics Polish Academy of Sciences, ul. Sokołowska 29/37, 01-142 Warsaw, PolandResults of dielectric studies in the nematic and isotropic liquid phases of pentylcyanobiphenyl (5CB), a model rod-like liquid crystalline material, are shown. They are based on the discussion of the evolution of dielectric constant (<inline-formula> <math display="inline"> <semantics> <mi>ε</mi> </semantics> </math> </inline-formula>), its changes under the strong electric field (nonlinear dielectric effect, NDE), and finally, the primary relaxation time. It is shown that changes in <inline-formula> <math display="inline"> <semantics> <mrow> <mi>ε</mi> <mfenced> <mi>T</mi> </mfenced> </mrow> </semantics> </math> </inline-formula> and NDE are entirely dominated by the impact of pretransitional fluctuations (pre-nematic and pre-isotropic, respectively) which are associated with the weakly discontinuous character of the isotropic–nematic phase transition. This influence also extends for the low-frequency, ionic species dominated, region. Notable, that the derivative-based and distortions sensitive analysis revealed the tricritical nature of the I-N transition. Although the glass transition in 5CB occurs in the deeply supercooled state at <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi>g</mi> </msub> <mo>≈</mo> <mo>−</mo> <mn>68</mn> <mtext> </mtext> <mo>°</mo> <mi mathvariant="normal">C</mi> </mrow> </semantics> </math> </inline-formula>, the dynamics (changes of the primary relaxation time) follow a previtreous pattern both in the isotropic and in the nematic phase. Finally, the discussion of the ’<i>molecular</i>’ vs. ‘<i>quasi-critical</i>’ characterizations of the isotropic and nematic phases is presented. It shows the evident prevalence of the ‘quasi-critical-picture’, which offers the consistent temperature parameterization in the total tested temperature range.https://www.mdpi.com/2073-4352/10/4/297Liquid crystalscritical behaviorprevitreous dynamicsdielectric properties |
| spellingShingle | Aleksandra Drozd-Rzoska ‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material Crystals Liquid crystals critical behavior previtreous dynamics dielectric properties |
| title | ‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material |
| title_full | ‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material |
| title_fullStr | ‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material |
| title_full_unstemmed | ‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material |
| title_short | ‘Quasi-Tricritical’ and Glassy Dielectric Properties of a Nematic Liquid Crystalline Material |
| title_sort | quasi tricritical and glassy dielectric properties of a nematic liquid crystalline material |
| topic | Liquid crystals critical behavior previtreous dynamics dielectric properties |
| url | https://www.mdpi.com/2073-4352/10/4/297 |
| work_keys_str_mv | AT aleksandradrozdrzoska quasitricriticalandglassydielectricpropertiesofanematicliquidcrystallinematerial |