Title离子液体1-烷基-3-甲基咪唑四氟硼酸盐在水溶液中的聚集行为
Other TitlesAggregation Behavior of 1-Alkyl-3-methylimidazolium Tetrafluoroborate Ionic Liquids in Aqueous Solutions
Authors付素珍
陈庆德
沈兴海
Affiliation北京大学化学与分子工程学院,放射化学与辐射化学重点学科实验室,北京分子科学国家实验室,北京100871
Keywords离子液体
1-烷基-3-甲基咪唑四氟硼酸盐
等温滴定量热
荧光
电导
Ionic liquids
1-Alkyl-3-methylimidazolium tetrafluoroborate
Isothermal titration calorimetry
Fluorescence
Conductivity
Issue Date2011
Publisher物理化学学报
Citation物理化学学报.2011,27,(8),1913-1918.
Abstract采用等温滴定量热法、静态荧光猝灭法和电导法系统研究了典型离子液体1-烷基-3-甲基咪唑四氟硼酸盐([Cnmim][BF4])在水溶液中的聚集行为,获得了胶束形成的临界胶束浓度(cmc),摩尔焓变(△Hmic),摩尔吉布斯自由能变(△Gmic),摩尔熵变(△Smic)以及不同浓度时[Cnmim][BF4]胶束的平均聚集数等基本参数.发现这类离子液体的聚集为熵驱动,阳离子的烷基链越长,△Gmic越负,聚集更容易发生.此外,结合[Cnmim]X (X=CI-,Br)的相关研究发现,阳离子相同时,体积越大和疏水性越强的阴离子与头基的结合能力越强,能有效地降低头基之间的静电排斥,降低cmc,利于胶束的形成.对于[C12mim][BF,],添加剂β-环糊精(β-CD)的加入可使cmc增大,△Hmic和△Smic减小,而KBF4则可使cmc和△Hmic减小,△Smic增大.
The aggregation behavior of 1-alkyl-3-methylimidazolium tetrafluoroborate ([C(n)mim][BF4]) ionic liquids in aqueous solutions was investigated by isothermal titration calorimetry (ITC), fluorescence quenching, and conductivity methods. The critical micelle concentration (cmc), the changes of the enthalpy (Delta H-mic), the Gibbs free energy (Delta G(mic)), and the entropy (Delta S-mic) for the micelle formation and the mean aggregation number of the micelles at different concentrations were obtained. We found that entropy was the principle driving force leading to the micellization of these types of ionic liquids. The increase in alkyl chain length led to a decrease in Delta G(mic), favoring the formation of micelles. Furthermore, by combining with the aqueous solution data for [C(n)mim]X (X=Cl-, Br-), the effect of anions on the aggregation behavior of the ionic liquids was investigated. The increase in the hydrophobicity and the volume of the anions favored the formation of micelles when the ionic liquids contained identical cations. This is believed to result from the decrease in electrostatic repulsion between the head groups in the micelles because of the relatively strong binding between the anions and the cations. With respect to [C(12)mim][BF4], the addition of beta-cyclodextrin (beta-CD) caused an increase in its cmc and a decrease in Delta H-mic and Delta S-mic; while the presence of KBF4 caused a decrease in cmc and Delta H-mic, and an increase in Delta S-mic.
URIhttp://hdl.handle.net/20.500.11897/80075
ISSN1000-6818
DOI10.3866/PKU.WHXB20110713
IndexedSCI(E)
中文核心期刊要目总览(PKU)
中国科技核心期刊(ISTIC)
中国科学引文数据库(CSCD)
Appears in Collections:化学与分子工程学院

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