Hidrojen bağlı 5BA/nCB (n=5-8) sıvı kristal karışımların mezojenik özelliklerinin incelenmesi
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Tarih
2023-09-28
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Yayıncı
Batman Üniversitesi Lisansüstü Eğitim Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Bu tez çalışmasında, 4-pentilbenzoik asit (5BA), 4-pentil–4'-siyanobifenil (5CB), 4-hekzil–4'-siyanobifenil (6CB), 4-heptil–4'-siyanobifenil (7CB) ve 4-oktil–4'-siyanobifenil (8CB) mezojenik kimyasallarından 5BA/5CB, 5BA/6CB, 5BA/7CB ve 5BA/8CB homojen sıvı kristal karışımları üretilmiştir. Üretilen karışımların termal analizleri Diferansiyel Taramalı Kalorimetre (DSC) cihazı ile gerçekleştirilmiştir. DSC verileri kullanılarak sıvı kristal mezojenik fazların faz geçiş sıcaklığı, entalpi, entropi ve faz geçiş düzeni gibi sıvı kristalik özellikleri araştırılmıştır. DSC sonuçları devamlı ısıtma ve soğutma esnasında kristal-smektik, smektik-nematik ve nematik-izotropik faz dönüşümlerini işaret eden piklerin oluştuğunu göstermiştir. Mezojenik faz dönüşümlerin genellikle 1. düzende gerçekleştiği ve soğutma sırasında gerçekleşen dönüşümlerin daha düzenli olduğu görülmüştür. Soğutma sırasında gözlenen mezofaz alanının ısıtma sırasında gözlenen mezofaz alanından daha geniş olduğu ve 5CB/8CB sıvı kristal karışımının mezofaz alanının yaklaşık 102 oC ile diğer karışımlara göre daha yüksek olduğu bulunmuştur. Üretilen karışımların morfolojik faz yapıları Polarize Optik Mikroskop (POM) ile araştırılmıştır ve faz geçiş sıcaklık değerlerinin DSC ile elde edilen faz geçiş sıcaklık değerleri ile uyumlu olduğu görülmüştür. Eşit kütle oranında üretilen 5BA/5CB, 5BA/6CB, 5BA/7CB, 5BA/8CB ikili karışımların Fourier Dönüşümlü İnfrared Spektroskopisi (FTIR) analiz sonuçları molekül içi bağlarının korunduğu ve karışımı oluşturan bileşenlerin molekülleri arasında hidrojen bağlarının oluştuğu gözlenmiştir. Sentezlenen sıvı kristal karışımların kristal durumundaki mikroyapı özellikleri X-ışını difraksiyonu (XRD) ile araştırılmıştır. XRD sonuçları kullanılarak moleküller arası bazal mesafe değerleri hesaplanmıştır. Üretilen sıvı kristalik karışımların kristalik yapılarında moleküler dizilimin monoklinik yapıda olduğu bulunmuştur.
In this thesis, homogeneous liquid crystal mixtures of equal mass 5BA/5CB, 5BA/6CB, 5BA/7CB and 5BA/8CB were produced from 4-pentylbenzoic acid (5BA), 4-pentyl-4'-cyanobiphenyl (5CB), 4-hexyl-4'-cyanobiphenyl (6CB), 4-heptyl-4'-cyanobiphenyl (7CB) and 4-octyl-4'-cyanobiphenyl (8CB) mesogenic chemicals. Thermal analyzes of the produced mixtures were performed with a Differential Scanning Calorimetry (DSC) device. Liquid crystalline properties such as phase transition temperature, enthalpy, entropy and phase transition order of liquid crystal mesogenic phases were investigated using DSC data. DSC results showed that phase transition peaks indicating crystal-smectic, smectic-nematic and nematic-isotropic phase transformations were formed during continuous heating and cooling cycle. It has been observed that mesogenic phase transformations generally occur in the 1st order and the transformations that occur during cooling are more regular. It was found that the mesophase range observed during cooling was wider than the mesophase range observed during heating, and the mesophase area of the 5CB/8CB liquid crystal mixture was higher at approximately 102 oC compared to the other mixtures. The morphological phase structures of the produced mixtures were investigated with Polarized Optical Microscope (POM) and it was seen that the phase transition temperature values were compatible with the phase transition temperature values obtained with DSC. Fourier Transform Infrared Spectroscopy (FTIR) analysis results of binary mixtures of 5BA/5CB, 5BA/6CB, 5BA/7CB, 5BA/8CB taken in equal mass showed that intramolecular bonds were preserved and hydrogen bonds were formed between the molecules of the components forming the mixture. The crystalline microstructure properties of the synthesized liquid crystal mixtures were investigated by X-ray diffraction (XRD). Basal intermolecular distance values were calculated using XRD results. It was found that the molecular arrangement in the crystalline structures of the liquid crystalline mixtures produced was monoclinic structure.
In this thesis, homogeneous liquid crystal mixtures of equal mass 5BA/5CB, 5BA/6CB, 5BA/7CB and 5BA/8CB were produced from 4-pentylbenzoic acid (5BA), 4-pentyl-4'-cyanobiphenyl (5CB), 4-hexyl-4'-cyanobiphenyl (6CB), 4-heptyl-4'-cyanobiphenyl (7CB) and 4-octyl-4'-cyanobiphenyl (8CB) mesogenic chemicals. Thermal analyzes of the produced mixtures were performed with a Differential Scanning Calorimetry (DSC) device. Liquid crystalline properties such as phase transition temperature, enthalpy, entropy and phase transition order of liquid crystal mesogenic phases were investigated using DSC data. DSC results showed that phase transition peaks indicating crystal-smectic, smectic-nematic and nematic-isotropic phase transformations were formed during continuous heating and cooling cycle. It has been observed that mesogenic phase transformations generally occur in the 1st order and the transformations that occur during cooling are more regular. It was found that the mesophase range observed during cooling was wider than the mesophase range observed during heating, and the mesophase area of the 5CB/8CB liquid crystal mixture was higher at approximately 102 oC compared to the other mixtures. The morphological phase structures of the produced mixtures were investigated with Polarized Optical Microscope (POM) and it was seen that the phase transition temperature values were compatible with the phase transition temperature values obtained with DSC. Fourier Transform Infrared Spectroscopy (FTIR) analysis results of binary mixtures of 5BA/5CB, 5BA/6CB, 5BA/7CB, 5BA/8CB taken in equal mass showed that intramolecular bonds were preserved and hydrogen bonds were formed between the molecules of the components forming the mixture. The crystalline microstructure properties of the synthesized liquid crystal mixtures were investigated by X-ray diffraction (XRD). Basal intermolecular distance values were calculated using XRD results. It was found that the molecular arrangement in the crystalline structures of the liquid crystalline mixtures produced was monoclinic structure.
Açıklama
Anahtar Kelimeler
DSC, Faz Geçişleri, FTIR, Sıvı Kristal Karışımlar, XRD, PhaseTransitions, Liquid Crystal Mixtures
Kaynak
WoS Q Değeri
Scopus Q Değeri
Cilt
Sayı
Künye
Bayram, E. (2023). Hidrojen bağlı 5BA/nCB (n=5-8) sıvı kristal karışımların mezojenik özelliklerinin incelenmesi. (Yayınlanmamış Yüksek Lisans Tezi). Batman Üniversitesi Lisansüstü Eğitim Enstitüsü, Batman.
