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Phase Behavior of Liquid Crystals Formed in [C12mim]Cl/H2O and [C12mim]Cl/Alcohols Systems
Mei-shan Pei,Zhi-yan Wu,Lu-yan Wang*,Xin-zhou Wu,Xu-tang Tao*
Author NameAffiliationE-mail
Mei-shan Pei School of Chemistry and Chemical Engineering, University of Jinan, Ji'nan 250022, China  
Zhi-yan Wu School of Chemistry and Chemical Engineering, University of Jinan, Ji'nan 250022, China  
Lu-yan Wang* School of Chemistry and Chemical Engineering, University of Jinan, Ji'nan 250022, ChinaState Key Laboratory of Crystal Material, Shandong University, Ji'nan 250100, China chm_wangly@ujn.edu.cn 
Xin-zhou Wu School of Chemistry and Chemical Engineering, University of Jinan, Ji'nan 250022, China  
Xu-tang Tao* State Key Laboratory of Crystal Material, Shandong University, Ji'nan 250100, China chm_wangly@ujn.edu.cn 
Abstract:
Phase behaviors of different binary systems involving 1-dodecyl-3-methylimidazolium chlo-ride ([C12mim]Cl) and H2O, [C12mim]Cl and different alcohols (1-butanol, 1-pentanol, 1-hexanol and 1-octanol) are investigated at 25 °C. Hexagonal liquid crystal phase (H1) is identified in [C12mim]Cl/H2O system, and lamellar liquid-crystalline (Lα) phase is found in [C12mim]Cl/alcohols systems by using polarized optical microscopy and small-angle X-ray scattering techniques. The formation of such phases is considered as a synergetic result of the solvatophobic force and the hydrogen-bonded network comprising an imidazolium ring,chloride ion and water (or alcohols), which can be confirmed by Fourier transform infrared spectra. It is noticeable that in [C12mim]Cl/1-octanol system, the lattice spacings of lamel-lar phase increase with increasing C12mimCl concentration, which is opposite to the results of [C12mim]Cl/H2O system. This may result mainly from stronger static repulsion among hydrophilic headgroups of imidazolium salts arranged in the bilayers of lamellar structures.Further measurements by diffrential scanning calorimetry indicate that the lamellar phase is stable within a wide temperature range above room temperature. However, the lattice spacings decrease with the increase of temperature, which may be due to the softening of the hydrocarbon chain of [C12mim]Cl molecules. In different alcohols systems, it is found that the lamellar lyotropic liquid crystal structure is easier to be formed when the carbon chain length becomes longer.
Key words:  1-dodecyl-3-methylimidazolium chloride, Lyotropic liquid crystal, Differential scanning calorimetry, Small-angle X-ray scattering
FundProject:
Phase Behavior of Liquid Crystals Formed in [C12mim]Cl/H2O and [C12mim]Cl/Alcohols Systems
裴梅山,吴芝燕,王庐岩*,吴馨洲,陶绪堂*
摘要:
利用偏光显微镜及小角X射线散射研究了25 °C下由1-十二烷基-3-甲基咪唑氯化物[C12mim]Cl和水、[C12mim]Cl和不同的醇(正丁醇、正戊醇、正己醇、正辛醇)所形成的二元体系的相行为. 结果表明:[C12mim]Cl和水可以形成六角相,其晶格参数随[C12mim]Cl含量的增多而递减;[C12mim]Cl和不同的醇可以形成层状相,且醇的碳链越长,层状相越易形成. 与水做溶剂相比,在[C12mim]Cl/辛醇体系中,随[C12mim]Cl含量的增加,层状相的层间距反而增大. 通过变温小角X射线散射和差示扫描量热法研究表明:层状相在高于室温的较大温度范围内是稳定的. 由于温度升高使[C12mim]Cl的碳氢链变软并易于缠结,导致层间距随温度的升高而减小. 通过红外光谱可以证明包含咪唑头基、氯离子和辛醇的氢键网络的存在. 疏溶剂力和氢键网络的协同作用是[C12mim]Cl能形成六角相和层状相的关键.
关键词:  [C12mim]Cl,溶致液晶,差示扫描量热法,小角X射线散射,傅立叶红外吸收光谱
DOI:10.1088/1674-0068/22/05/453-459
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