Effects of protonation of alkyldimethylamine oxides on the dissolution temperature in aqueous media.
Effects of protonation of alkyldimethylamine oxides on the dissolution temperature in aqueous media.
复制标题
烷基二甲胺氧化物的质子化对水介质中溶解温度的影响。
DOI：
10.1006/jcis.2002.8458
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发表时间：
2002
影响因子：
9.9
通讯作者：
H. Maeda
中科院分区：
文献类型：
--
作者：
H. Kawasaki;Kazumasa Ookuma;H. Maeda
采用差示扫描量热法研究了十六烷基二甲基氧化胺质子化（电离）对溶解温度的影响。只有一个吸热峰可重复地观察到在所有的电离度α检查，被分配到从固体（凝胶相）的过渡到含有胶束的溶液。溶解温度与α曲线显示在α = 0.5处最大，强烈表明通过所提出的氢键形成非离子和阳离子物质的1：1组合物的稳定复合物。从溶解曲线的形状以及固相的组成分析，发现在所有α值上形成固溶体。还检查了α = 0.5和α = 1时烷基链长度对十八烷基-（C18DAO）、十六烷基-（C16DAO）和十四烷基二甲基氧化胺（C14DAO）的同源系列的溶解温度的影响。转变温度和相关的热力学量Δ H和Δ S都随链长系统地增加，但对于α = 0.5，观察到Δ H和Δ S值随链长的较小增加[Δ H/CH2（kJ mol（-1））= 7.2 +/-0.2和2.2 +/-0.5（α = 1和α = 0.5），Δ S/CH2（J mol（-1）K（-1））= 21.9 +/-1.8（α = 1）和4.6 +/-1.9（α = 0.5）]。通过退火程序，证明了C16DAO（α = 1）固体的凝胶相的亚稳性质。
The effects of protonation (ionization) of hexadecyldimethylamine oxides on the dissolution temperature in aqueous media were investigated by differential scanning calorimetry. Only one endothermic peak was reproducibly observed at all the degrees of ionization alpha examined that were assigned to the transition from the solid (the gel phase) to the solution containing micelles. The dissolution temperature versus alpha curves showed a maximum at alpha=0.5, strongly suggesting the formation of a stable complex of 1-to-1 composition of the nonionic and cationic species through the proposed hydrogen bond. From the shape of the dissolution curve as well as the composition analysis of the solid phase, the solid solution was found to be formed over all alpha values. Effects of alkylchain length on the dissolution temperature for a homologous series of octadecyl- (C18DAO), hexadecyl- (C16DAO), and tetradecyldimethylamine oxide (C14DAO) were also examined for alpha=0.5 and alpha=1. Both the transition temperature and the associated thermodynamic quantities DeltaH and DeltaS increased systematically with the chain length, but for alpha=0.5 smaller increases in DeltaH and DeltaS values with the chain length were observed [DeltaH/CH2 (kJ mol(-1))=7.2+/-0.2 and 2.2+/-0.5 for alpha=1 and alpha=0.5, respectively, and DeltaS/CH2 (J mol(-1) K(-1))=21.9+/-1.8 for alpha=1 and 4.6+/-1.9 for alpha=0.5]. By annealing procedures, the metastable nature of the gel phase was demonstrated for the C16DAO (alpha=1) solid.