Crystallisation of sodium dodecyl sulfate–water micellar solutions with structurally similar additives: counterion variation

摘要: The effects of a series structurally similar sodium dodecyl sulfate (SDS) additives on the crystallisation SDS–water micellar solutions were investigated using combination differential scanning calorimetry, dynamic light scattering, optical microscopy and inductively coupled plasma emission spectroscopy. Seven different counterions chosen from groups 1 2 periodic table to replace SDS: LDS, (SDS), KDS, RbDS, CsDS, Mg(DS)2, Ca(DS)2 Sr(DS)2. Two representative temperature profiles employed – linear cooling ramps at rate 0.5 °C min−1 determine near-equilibrium kinetics transitions isothermal holds 6 elucidate morphological changes. Crystallisation reference solution 20% SDS–H2O with 0.25, 1.0 2.5% additive was generally promoted or inhibited even lowest concentrations. Melting points however remained largely unchanged, suggesting that predominantly had kinetic rather than thermodynamic effect. ICP-OES measurements for containing 1% indicated most integrated into SDS crystals which reflected by changes, including formation hexagonal oval shaped crystals. Our results both quantify provide insight effect solutions, can readily form due preferential Na exchange.