Bazı Üçlü Karıştırılmış Hidrojen Bağlı Sıvı Kristallerin Termal özelliklerine 4-oktiloksi-4'-siyanobifenil (8OCB) mezojeninin etkisi

4-Hekzilbenzoik asit (6BA), 4- (oktiloksi) benzoik asit (8OBA) ve 4- (desiloksi) benzoik asit (10OBA)'ten 1:1:1 ağırlık oranında üretilen üçlü karışımların termal ve sıvı kristalik davranışlarına sıvı kristal 4oktiloksi-4'-siyanobifenil (8OCB) etkisi, diferansiyel tarama kalorimetresi (DSC) ile ve tespit edilen mezofazlar polarize ışık mikroskobu (PLM) ile araştırıldı. DSC deneylerinde ölçülen faz geçiş sıcaklıkları PLM gözlemleri ile uyumludur. Deneysel sonuçlar yeni kompleks karışımların da saf sıvı kristal özelliklerini sergilediğini göstermektedir. Hazırlanan tüm homolog kompleks karışımların morfolojik yapılarının smektogenik ve nematik mezofaz olduğu bulunmuştur. 8OCB eklenmesi ile üretilen yeni kompleks karışımın nematik aralığı, hem saf 8OCB'nin hem de 6BA/8OBA/10OBA karışımının nematik alanlarından daha büyük olduğu tespit edilmiştir. Ayrıca, kompleks karışımda 8OCB'nin ağırlık oranı artışıyla nematik-izotropik geçiş sıcaklığının azaldığı görüldü. Üstelik, ısıtma oranı arttıkça kompleks karışımın faz geçiş sıcaklık ve entalpi değişim değerleri artmıştır, ve hesaplanan aktivasyon enerjisi yeni kompleks karışımların iyi bir nematik termal stabiliteye sahip olduğunu göstermiştir

Effect of 4-octyloxy-4′-cyanobiphenyl Mesogen on Thermal Properties of Some Ternary Mixed Hydrogen-bonded Liquid Crystals

The effect of liquid crystal 4-octyloxy-4′-cyanobiphenyl (8OCB) on thermal and liquid crystalline behaviours of ternary mixtures produced at weight ratio of 1:1:1 from 4-hexylbenzoic acid (6BA), 4- (octyloxy)benzoic acid (8OBA) and 4-(decyloxy)benzoic acid (10OBA), were investigated by differential scanning calorimeter (DSC) and mesophases identified by polarized light microscopy (PLM). The phase transition temperatures evaluated in the DSC experiments are in line with the PLM observations. The experimental results show that the novel complex mixtures also have displayed pure liquid crystalline properties. The morphologic structures of all prepared homolog complex mixtures were found to be smectogenic and nematic mesophase. The nematic range of the novel complex mixture produced by adding 8OCB was found to be bigger than the nematic ranges of both the pure 8OCB and the 6BA/8OBA/10OBA mixture. Also, it was seen that the nematic-isotropic transition temperature decreased with increasing the weight ratio of 8OCB in the complex mixture. Furthermore, the phase transition temperatures and enthalpy change values of the complex mixture increased as heating ratio increased, and the calculated activation energy showed that the novel complex mixtures had a good nematic thermal stability

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