Abstract

Herein, the interaction of sodium alginate (SA) with cetyltrimethylammonium bromide (CTAB) has been studied in aqueous solution as well as in aqua-organic mixed solvents at varying temperatures using conductivity measurements. Ethylene glycol (EG), dimethyl formamide (DMF), 1,4-dioxane (DO), and acetonitrile (AN) were used as organic solvents. The CMC values for SA + CTAB system in 10% (v/v) mixed solvents follow the order: CMC_{water + DO} > CMC_{water + DMF} > CMC_{water + AN} > CMC _{water + EG} > CMC_water. The CMC values for the SA + CTAB system in aqueous medium indicate that SA lowers the CMC of pure CTAB. The higher CMC values in all the solvent mixtures may be due to the decrease of the dielectric constant and cohesive energy density of water. The interaction of SA with CTAB is affected significantly by the change in temperature which is attributed to changes in hydration of SA and CTAB. The negative values of free energy of micellization (${\Delta G}_m^o$) for the SA + CTAB system imply the spontaneous aggregation phenomenon and the negative ${\Delta G}_m^o$ values in H₂O and 10% (v/v) mixed solvents follow the trend: ${\Delta G}_m^o$ (H₂O) > ${\Delta G}_m^o$ (water + EG) > ${\Delta G}_m^o$ (water + DMF) > ${\Delta G}_m^o$ (water + DO) > ${\Delta G}_m^o$ (water + AN). The values of free energy changes of transfer (${\Delta G}_{m,t}^o$) were also evaluated for the shift of SA + CTAB mixture from water to aqua-organic mixed solvents and discussed the results in detail. The binding interactions of SA with CTAB are proposed to be hydrogen bonding, ion-dipole, and hydrophobic interactions. The enthalpy-entropy compensation of SA + CTAB systems was assessed and illustrated in detail.

摘要

在此，海藻酸钠 (SA) 与十六烷基三甲基溴化铵 (CTAB) 的相互作用已经在不同温度下的水溶液以及水有机混合溶剂中使用电导率测量进行了研究。乙二醇 (EG)、二甲基甲酰胺 (DMF)、1,4-二恶烷 (DO) 和乙腈 (AN) 用作有机溶剂。SA + CTAB 系统在 10% (v/v) 混合溶剂中的 CMC 值顺序为：CMC_{水 + DO} > CMC_{水 + DMF} > CMC_{水 + AN} > CMC_{水 + EG} > CMC_水. SA + CTAB 体系在水性介质中的 CMC 值表明 SA 降低了纯 CTAB 的 CMC。所有溶剂混合物中较高的 CMC 值可能是由于水的介电常数和内聚能密度降低。SA 与 CTAB 的相互作用受到温度变化的显着影响，温度变化归因于 SA 和 CTAB 的水合变化。胶束化自由能的负值 (${\Delta G}_{米}^{○}$) 对于 SA + CTAB 系统意味着自发聚集现象和负${\Delta G}_{米}^{○}$H ₂ O 和 10% (v/v) 混合溶剂中的值遵循以下趋势：${\Delta G}_{米}^{○}$(H ₂ O) >${\Delta G}_{米}^{○}$(水 + EG) >${\Delta G}_{米}^{○}$(水 + DMF) >${\Delta G}_{米}^{○}$(水 + DO) >${\Delta G}_{米}^{○}$（水 + AN）。转移的自由能变化值 (${\Delta G}_{米,吨}^{○}$) 还评估了 SA + CTAB 混合物从水到水有机混合溶剂的转变，并详细讨论了结果。SA 与 CTAB 的结合相互作用被认为是氢键、离子偶极子和疏水相互作用。对 SA + CTAB 系统的焓熵补偿进行了评估和详细说明。