High-resolution calorimetric study of the nematic to smectic- A transition in aligned liquid crystal–aerosil gels
High-resolution ac calorimetry has been used to study the nematic to smectic-A (N-SmA) phase transition in the liquid crystal octylcyanobiphenyl (8CB) confined in aligned colloidal aerosil gels. A stable and robust nematic alignment was achieved by repeated thermal cycling of the samples in the pres...
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| Format: | Article |
| Language: | en_US |
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American Physical Society
2010
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| Online Access: | http://hdl.handle.net/1721.1/51743 https://orcid.org/0000-0002-6458-1866 |
| _version_ | 1826203524011130880 |
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| author | Garland, Carl W. Iannacchione, G. S. |
| author2 | Massachusetts Institute of Technology. Department of Chemistry |
| author_facet | Massachusetts Institute of Technology. Department of Chemistry Garland, Carl W. Iannacchione, G. S. |
| author_sort | Garland, Carl W. |
| collection | MIT |
| description | High-resolution ac calorimetry has been used to study the nematic to smectic-A (N-SmA) phase transition in the liquid crystal octylcyanobiphenyl (8CB) confined in aligned colloidal aerosil gels. A stable and robust nematic alignment was achieved by repeated thermal cycling of the samples in the presence of a strong uniform magnetic field. In some ways (such as transition temperature and integrated enthalpy), the dependence of the specific heat peak associated with the N-SmA transition on the aerosil density for aligned gels is consistent with that observed in unaligned (random) gel samples. However, a power-law analysis reveals that the behavior of the critical exponent α is quite different. For random gels, α varies gradually with aerosil density, whereas we find that α for aligned gels shifts abruptly to an XY-like value for the lowest aerosil density studied and remains essentially constant as the sil density increases. This aerosil density independence of α is consistent with the critical behavior of the smectic correlation lengths obtained from an x-ray scattering study of 8CB in aligned aerosil gels. The combined calorimetric and x-ray results indicate that the role of quenched randomness in aligned gels of 8CB+sils differs significantly from that in random gels. |
| first_indexed | 2024-09-23T12:38:43Z |
| format | Article |
| id | mit-1721.1/51743 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T12:38:43Z |
| publishDate | 2010 |
| publisher | American Physical Society |
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| spelling | mit-1721.1/517432022-10-01T10:14:48Z High-resolution calorimetric study of the nematic to smectic- A transition in aligned liquid crystal–aerosil gels Garland, Carl W. Iannacchione, G. S. Massachusetts Institute of Technology. Department of Chemistry Garland, Carl W. Garland, Carl W. High-resolution ac calorimetry has been used to study the nematic to smectic-A (N-SmA) phase transition in the liquid crystal octylcyanobiphenyl (8CB) confined in aligned colloidal aerosil gels. A stable and robust nematic alignment was achieved by repeated thermal cycling of the samples in the presence of a strong uniform magnetic field. In some ways (such as transition temperature and integrated enthalpy), the dependence of the specific heat peak associated with the N-SmA transition on the aerosil density for aligned gels is consistent with that observed in unaligned (random) gel samples. However, a power-law analysis reveals that the behavior of the critical exponent α is quite different. For random gels, α varies gradually with aerosil density, whereas we find that α for aligned gels shifts abruptly to an XY-like value for the lowest aerosil density studied and remains essentially constant as the sil density increases. This aerosil density independence of α is consistent with the critical behavior of the smectic correlation lengths obtained from an x-ray scattering study of 8CB in aligned aerosil gels. The combined calorimetric and x-ray results indicate that the role of quenched randomness in aligned gels of 8CB+sils differs significantly from that in random gels. National Science Foundation 2010-02-12T15:29:15Z 2010-02-12T15:29:15Z 2009-01 2008-06 Article http://purl.org/eprint/type/JournalArticle 1550-2376 1539-3755 http://hdl.handle.net/1721.1/51743 Cruceanu, F. et al. “High-resolution calorimetric study of the nematic to smectic- A transition in aligned liquid crystal aerosil gels.” Physical Review E 79.1 (2009): 011710. © 2009 The American Physical Society. https://orcid.org/0000-0002-6458-1866 en_US http://dx.doi.org/10.1103/PhysRevE.79.011710 Physical Review E Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Physical Society APS |
| spellingShingle | Garland, Carl W. Iannacchione, G. S. High-resolution calorimetric study of the nematic to smectic- A transition in aligned liquid crystal–aerosil gels |
| title | High-resolution calorimetric study of the nematic to smectic- A transition in aligned liquid crystal–aerosil gels |
| title_full | High-resolution calorimetric study of the nematic to smectic- A transition in aligned liquid crystal–aerosil gels |
| title_fullStr | High-resolution calorimetric study of the nematic to smectic- A transition in aligned liquid crystal–aerosil gels |
| title_full_unstemmed | High-resolution calorimetric study of the nematic to smectic- A transition in aligned liquid crystal–aerosil gels |
| title_short | High-resolution calorimetric study of the nematic to smectic- A transition in aligned liquid crystal–aerosil gels |
| title_sort | high resolution calorimetric study of the nematic to smectic a transition in aligned liquid crystal aerosil gels |
| url | http://hdl.handle.net/1721.1/51743 https://orcid.org/0000-0002-6458-1866 |
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