Kartashynska Elena S, Vysotsky Yuri B, Vollhardt Dieter, Fainerman Valentin B, Zakharov Anatoly Yu
L.M. Litvinenko Institute of Physical Organic and Coal Chemistry, 70 R. Luxemburg Str., 83114 Donetsk, Ukraine.
Yaroslav-the-Wise Novgorod State University, 41, B. S.-Peterburgskaya Str., 173003 Veliky Novgorod, Russia.
ACS Omega. 2018 Dec 5;3(12):16693-16705. doi: 10.1021/acsomega.8b02583. eCollection 2018 Dec 31.
The thermodynamic parameters of formation and clusterization of aliphatic alcohols C HOH and carboxylic acids C HCOOH ( = 6-16) are calculated using the quantum-chemical semiempirical PM3 method. Four types of dimers are constructed in two directions of the spread monolayer comprising the most energetically advantageous monomer structures. The hydrophobic chains of alcohol and carboxylic acid molecules in the regarded dimers are found to be tilted within 12° to the normal of the spread monolayer. The structures of the mixed and pure surfactant dimers are the basis for the mixed alcohol-carboxylic acid monolayers of the following types: two dimensional (2D) film 1 with single distribution of the individual component in the other one, when the molecules of the first component do not interact with each other but are completely surrounded by the molecules of the second component; 2D film 2 with domain structure, when the film consists of "islands" of the individual components. The dependences of the clusterization Gibbs' energy per one monolayer molecule on the molar fraction of the components for the mixed 2D films 1 formed by surfactants with equal alkyl chain length are found to be limited from top to bottom by the corresponding dependences for pure components. This indicates the absence of synergetic interaction between the hydrophilic head groups of carboxylic acids and alcohols and conforms to the available experimental data. The formation of the described types of mixed films is competitive. The preferential formation of 2D films 1 with single distribution of the first component among the molecules of the second one is possible when the length of the carboxylic acid hydrocarbon chain is longer by Δ = 1-2 methylene units than that of the corresponding alcohol alkyl chain. According to the fractionally linear law, the highest possible content of the carboxylic acids in such 2D films 1 depends on the Δ value and does not exceed 33.3%.
使用量子化学半经验PM3方法计算脂肪醇CₙH₂ₙ₊₁OH和羧酸CₙH₂ₙ₋₁COOH（n = 6 - 16）的生成和聚集热力学参数。在包含能量最有利单体结构的扩展单分子层的两个扩展方向上构建了四种类型的二聚体。发现所考虑的二聚体中醇和羧酸分子的疏水链相对于扩展单分子层的法线倾斜12°以内。混合和纯表面活性剂二聚体的结构是以下类型的混合醇 - 羧酸单分子层形成的基础：二维（2D）膜I，其中一种组分在另一种组分中呈单分布，此时第一种组分的分子彼此不相互作用，但完全被第二种组分的分子包围；2D膜II，具有畴结构，此时膜由各组分的“岛”组成。对于由具有相等烷基链长度的表面活性剂形成的混合2D膜I，发现每一个单分子层分子的聚集吉布斯自由能对组分摩尔分数的依赖性在上下限上受到纯组分相应依赖性的限制。这表明羧酸和亲水头基之间不存在协同相互作用，并且与现有的实验数据相符。所描述类型的混合膜的形成是竞争性的。当羧酸烃链的长度比相应醇烷基链长Δ = 1 - 2个亚甲基单元时，在第二种分子中优先形成第一种组分呈单分布的2D膜I是可能的。根据分数线性定律，此类2D膜I中羧酸的最高可能含量取决于Δ值，且不超过33.3%。
