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Journals / İTÜ Dergisi Seri C: Fen Bilimleri / 2004 / Cilt: 2 - Sayı: 1

The phase transitions in liquid crystal polymers

Sıvı kristal polimerlerde faz geçişleri

Sevtap YILDIZ
Önder PEKCAN
Pages
90–98
Publication Date
2022-10-18
DOI
—
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AI Summary & Key Takeaways

AI Insight
⚡ TL;DR(Too Long; Didn't Read)

The effect of quenched random constraints introduced in GLC6 are consistent with the theory of quenched random interactions.

📌 3 Key Takeaways

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Objective & Hypothesis:The photon transmission technique was used to study the phase transitions of a liquid crystalline acrylate monomer, 6-(4-cyanobiphenyl-4'oxy)hexyl acrylate (LC6), its homopolymer (PLC6) and its graft copolymer (GLC6) with polytetrahydrofuran grafts.
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Key Findings & Data:We observed the phase transition sequence isotropic-nematic-smectic A-smectic C in the LC6 monomer.
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Conclusion & Impact:The effect of quenched random constraints introduced in GLC6 are consistent with the theory of quenched random interactions.
🔬Design:Research Article
📍Scope:Comprehensive Sample
⚙️Variables:Domain Parameters

Abstract

The photon transmission technique was used to study the phase transitions of a liquid crystalline acrylate monomer, 6-(4-cyanobiphenyl-4'oxy)hexyl acrylate (LC6), its homopolymer (PLC6) and its graft copolymer (GLC6) with polytetrahydrofuran grafts. The structure of the phases was identified by polarizing microscopy. The transition temperatures were also determined by polarizing microscopy, from changes in the characteristic texture of the phases observed under cross polarizers. We observed the phase transition sequence isotropic-nematic-smectic A-smectic C in the LC6 monomer. In LC6 monomer, the nematic-smectic A transition was found to be of second order as observed by Me Millan ratio. The effective critical exponent of the order parameter was found to be $beta$= 0.244 near the nematic-smectic A transition. The value of the exponent was very close to the tricritical value $beta_{TCP}$ = 0.25. Nematic-smectic A transition is first order in PLC6 and second order in GLC6, with the transition temperature remaining the same. It has been argued that first-order phase transitions are converted to second-order phase transitions by the introduction of frozen disorder into a system. The effect of quenched random constraints introduced in GLC6 are consistent with the theory of quenched random interactions.

Özet

Foton geçirgenliği yöntemi kullanılarak sıvı kristal akrilat monomer, (6-4-siyanobifenil-4'-oksi)hekzil akrilat (LC6), homopolimeri (PLC6) ve politetrahidrofuranla aşılanmış aşı kopolimerinin (GLC6) faz dönüşümleri incelendi. Faz dönüşümleri polarizasyon mikroskobuyla doğrulandı. LC6 monomerinde izotropik-nematik-smektik A-smectik C faz dönüşüm serisi gözlenirken PLC6 ve GLC6 polimerlerinde, nematik ve sinektik A fazları baskın görünmektedir. LC6 monomerinde nematik-smektik A faz dönüşümü ikinci dereceden olup düzen parametresi için efektif kritik üstel $beta$= 0.244 olarak hesaplandı. Gözlenen nematik-smektik A faz dönüşümü PLC6'da birinci derece ve GLC6'da ikinci derece olurken dönüşüm sıcaklığı aynı kalmaktadır. GLC6 'daki donmuş rastlantısal bağların etkisinin donmuş rastlantısal etkileşmelerin kuramsal sonuçlarıyla tutarlı olduğu görüldü. GLC6 aşı polimerinde nematik-smektik A faz dönüşümünde $beta$ kritik üsteli $beta$ = 0.532 olarak hesaplandı.

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Cite This Article

YILDIZ, S., PEKCAN, Ö. (2022). The phase transitions in liquid crystal polymers. İTÜ Dergisi Seri C: Fen Bilimleri, Cilt: 2 - Sayı: 1, 90–98. https://ajindex.com/articles/556903

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