Solution and Liquid Crystalline Properties of Sodium Lauroyl Methyl Isethionate/Water Mixtures

Abstract

The project contributes to the general theme of complex chemical systems andstrengthens ties with Innospec, a multi-national chemical company. Sodium lauroylmethyl isethionate (SLMI. Trade name "Iselux") is a newly developed surfactantwith attractive product properties for personal care applications. Little is knownabout the fundamental surface and solution properties of SLMI, and it is notcurrently possible to use information on available surfactants to predict phasebehaviour. We characterise the solution and liquid crystalline phase behaviour ofthe SLMI/water system using a combination of optical microscopy, x-ray scatteringand differential scanning calorimetry techniques.SLMI is synthesised using a batch process that leads to variable componentconcentrations. Preliminary studies conducted by Innospec indicate that thepresence of particular process components has a significant influence on SLMIformulation rheological properties. We investigate the effects of synthesis-derivedcomponents on the rheological properties of the SLMI/sodium {(3-(dodecanoylamino)propyl)(dimethyl)ammonio)}acetate/water system using rheology and lightscattering (static and dynamic) techniques.SLMI is often formulated into personal care products on mixing aqueousformulation components. Micelle growth occurs via a mechanistic process that isnot understood and the equilibrium viscosity is attained at a time after mixing thatranges from seconds to weeks. Developing an improved understanding of themicelle growth mechanism is of both academic and industrial value. We utilisestatic light scattering and nuclear magnetic resonance techniques to probe a rangeof samples in the viscoelastic region of the SLMI/(carboxymethyl)hexadecyldimethylammonium hydroxide/water system. Experimental findings improve ourcurrent understanding of micelle growth process and provide a platform for futureresearch on non-equilibrium mixing kinetics.In the final section we investigate salt-induced cloud point and precipitationphenomena in the SLMI/salt/water system. The cloud point is commonly observedin surfactant and protein systems by increasing the solution temperature above acritical value, resulting in phase separation of solute-rich and solute-depletedlayers. Cloud point induced phase separation may also be prompted by addition ofsalt. The mechanistic process driving electrolyte-induced cloud point phenomenais not understood. We use a combination of turbidimetry measurements and lightscattering (static and dynamic) techniques to measure cloud point curves andcharacterise micellar behaviour prior to clouding.

Date of Award	1 Aug 2015
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Robin Curtis (Supervisor)