Hidrojen bağlı 8OBA/ADA ikili kompleks sıvı kristalin termal ve mikroyapısal özellikleri
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Dosyalar
Tarih
2019-06-01
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Iğdır Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/openAccess
Attribution-ShareAlike 3.0 United States
Attribution-ShareAlike 3.0 United States
Özet
Bu çalışmada, mezojenik 4-oktiloksi benzoik asit (8OBA) ve mezojenik olmayan adipik asit (ADA)’in
ikili kompleksinden sentezlenen yeni bir sıvı kristalin termal özellikleri diferansiyel taramalı kalorimetre (DSC)
ve mikroyapı özellikleri polarize optik mikroskop (POM) ile incelenmiştir. 8OBA ve ADA arasında hidrojen
bağının oluştuğu zayıflatılmış toplam yansıma-kızılötesi spektroskopisi (ATR-IR) ile doğrulanmıştır. Ayrıca,
8OBA/ADA sıvı kristal kompleksinin kimyasal yapısı 1H-NMR çalışmasıyla incelenmiştir. DSC ve POM
sonuçları sentezlenen yeni sıvı kristal kompleksin sıvı kristalik özellikler sergilediğini göstermektedir.
8OBA/ADA ikili kompleksi, DSC ile sürekli ısıtma ve soğutma esnasında faz geçiş pikleri göstermektedir.
Soğutma esnasında gözlenen smektik C fazı sürekli ısıtma esnasında gözlenmemiştir. Sürekli ısıtma esnasında
elde edilen faz geçiş sıcaklık ve entalpi değişim değerleri, sürekli soğutma esnasında elde edilen faz geçiş
sıcaklık ve entalpi değişim değerlerinden daha yüksek, fakat nematik alan daha düşüktür. Ayrıca bu değerlerin
ısıtma oranına bağlılığı da araştırılmıştır. Isıtma oranı arttıkça faz geçiş sıcaklıklarının arttığı fakat entalpi
değerlerinin azaldığı gözlemlenmiştir. DSC ile ölçülen faz geçiş sıcaklık değerlerinin POM ile ölçülen faz geçiş
sıcaklık değerleri ile yaklaşık aynı olduğu görülmüştür. 8OBA/ADA sıvı kristal kompleksin faz geçişleri için
faz geçiş aktivasyon enerjileri hesaplanmıştır ve elde edilen değerler, faz sırasına göre faz geçiş aktivasyon
enerjilerinin arttığını göstermiştir. Bu sonuç da 8OBA/ADA sıvı kristal kompleksin faz geçişlerinin sürekli
ısıtma esnasında düzenli olarak gerçekleştiğini göstermektedir.
In this study, the phase transition temperatures and enthalpy changes of a novel liquid crystal synthesized from the binary complex of mesogenic 4-octyloxy benzoic acid (8OBA) and non-mesogenic adipic acid (ADA) were investigated by differential scanning calorimeter (DSC) and phase structures by polarized optical microscopy (POM). The hydrogen bonding that occurs between 8OBA and ADA was confirmed by attenuated total reflection- infrared spectroscopy (ATR-IR). In addition, the chemical structure of the 8OBA/ADA liquid crystal complex was studied by 1H-NMR study. The 1H-NMR results also showed that some chemical shifts occurred and a new liquid crystal was synthesized. According to DSC and POM results, it appears that the new liquid crystal complex synthesized exhibits liquid crystalline properties. The 8OBA/ADA binary complex shows phase transition peaks during continuous heating and cooling with DSC. The observed smectic C (SmC) phase during cooling was not observed during continuous heating. The phase transition temperature and enthalpy change values obtained during continuous heating are higher than the phase transition temperature and enthalpy change values obtained during continuous cooling, but the nematic range is lower. Also, the dependence of these values on the heating rate has been investigated. As the heating rate increased, it was seen that the phase transition temperatures increased but enthalpy values decreased. It was observed that the phase transition temperature values measured by DSC are approximately the same as the phase transition temperature values measured by POM. Phase transition activation energies for the phase transitions of the 8OBA/ADA liquid crystal complex were calculated using Kissinger, Ozawa and Takhor equations, and the values obtained indicated that the phase transition activation energies were increased relative to the phase sequence. This result shows that the phase transitions of 8OBA/ADA liquid crystal complex occur regularly during continuous heating.
In this study, the phase transition temperatures and enthalpy changes of a novel liquid crystal synthesized from the binary complex of mesogenic 4-octyloxy benzoic acid (8OBA) and non-mesogenic adipic acid (ADA) were investigated by differential scanning calorimeter (DSC) and phase structures by polarized optical microscopy (POM). The hydrogen bonding that occurs between 8OBA and ADA was confirmed by attenuated total reflection- infrared spectroscopy (ATR-IR). In addition, the chemical structure of the 8OBA/ADA liquid crystal complex was studied by 1H-NMR study. The 1H-NMR results also showed that some chemical shifts occurred and a new liquid crystal was synthesized. According to DSC and POM results, it appears that the new liquid crystal complex synthesized exhibits liquid crystalline properties. The 8OBA/ADA binary complex shows phase transition peaks during continuous heating and cooling with DSC. The observed smectic C (SmC) phase during cooling was not observed during continuous heating. The phase transition temperature and enthalpy change values obtained during continuous heating are higher than the phase transition temperature and enthalpy change values obtained during continuous cooling, but the nematic range is lower. Also, the dependence of these values on the heating rate has been investigated. As the heating rate increased, it was seen that the phase transition temperatures increased but enthalpy values decreased. It was observed that the phase transition temperature values measured by DSC are approximately the same as the phase transition temperature values measured by POM. Phase transition activation energies for the phase transitions of the 8OBA/ADA liquid crystal complex were calculated using Kissinger, Ozawa and Takhor equations, and the values obtained indicated that the phase transition activation energies were increased relative to the phase sequence. This result shows that the phase transitions of 8OBA/ADA liquid crystal complex occur regularly during continuous heating.
Açıklama
Anahtar Kelimeler
Hidrojen Bağlı Sıvı Kristaller, Termal Özellikler, Mikroyapı, DSC, POM, Hydrogen Bonded Liquid Crystals, Thermal Properties, Microstructure
Kaynak
WoS Q Değeri
N/A
Scopus Q Değeri
Cilt
9
Sayı
2
Künye
Sünkür, M., Okumuş, M. (2019). Hidrojen bağlı 8OBA/ADA ikili kompleks sıvı kristalin termal ve mikroyapısal özellikleri. Iğdır Üniversitesi Fen Bilimleri Enstitüsü Dergisi, 9 (2), ss. 956-966. https://doi.org/10.21597/jist.438081
