Biaxiality-induced magnetic field effects in bent-core nematics: molecular-field and Landau theory.

Abstract

Nematic liquid crystals composed of bent-core molecules exhibit unusual properties, including an enhanced Cotton-Mouton effect and an increasing isotropic (paranematic)-nematic phase transition temperature as a function of magnetic field. These systems are thought to be good candidate biaxial liquid crystals. Prompted by these experiments, we investigate theoretically the effect of molecular biaxiality on magnetic-field-induced phenomena for nematic liquid crystals, using both molecular field and Landau theory. The geometric mean approximation is used in order to specify the degree of molecular biaxiality using a single parameter. We reproduce experimental field-induced phenomena and predict also an experimentally accessible magnetic critical point. The Cotton-Mouton effect and temperature dependence of the paranematic-nematic phase transition are more pronounced with increased molecular biaxiality. We compare our theoretical approaches and make contact with recent relevant experimental results on bent-core molecular systems.

AI evidence extraction

Main findings

Using molecular-field and Landau theory, the authors reproduce experimentally observed magnetic-field-induced phenomena in bent-core nematic liquid crystals and predict an experimentally accessible magnetic critical point. The Cotton-Mouton effect and the temperature dependence of the paranematic-nematic phase transition are reported to become more pronounced with increased molecular biaxiality.

Outcomes measured

• Cotton-Mouton effect
• isotropic (paranematic)-nematic phase transition temperature
• magnetic-field-induced phenomena
• magnetic critical point (predicted)

Limitations

• The work is theoretical (molecular-field and Landau theory) rather than an experimental or epidemiological study.
• No magnetic field strength, frequency, or exposure duration is provided in the abstract.
• No biological population or health outcomes are studied.

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    "study_type": "other",
    "exposure": {
        "band": null,
        "source": "magnetic field",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "Cotton-Mouton effect",
        "isotropic (paranematic)-nematic phase transition temperature",
        "magnetic-field-induced phenomena",
        "magnetic critical point (predicted)"
    ],
    "main_findings": "Using molecular-field and Landau theory, the authors reproduce experimentally observed magnetic-field-induced phenomena in bent-core nematic liquid crystals and predict an experimentally accessible magnetic critical point. The Cotton-Mouton effect and the temperature dependence of the paranematic-nematic phase transition are reported to become more pronounced with increased molecular biaxiality.",
    "effect_direction": "unclear",
    "limitations": [
        "The work is theoretical (molecular-field and Landau theory) rather than an experimental or epidemiological study.",
        "No magnetic field strength, frequency, or exposure duration is provided in the abstract.",
        "No biological population or health outcomes are studied."
    ],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "bent-core molecules",
        "nematic liquid crystals",
        "molecular biaxiality",
        "magnetic field effects",
        "Cotton-Mouton effect",
        "Landau theory",
        "molecular-field theory",
        "paranematic-nematic transition",
        "magnetic critical point"
    ],
    "suggested_hubs": []
}

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