Highly viscous wormlike micellar phases formed from the mixed AOT/C14DMAO/H2O system

Tang

Wang

2017

J Surfact & Detergents

The phase behavior and rheological properties of a multi‐component system, made of a zwitterionic surfactant cocoamidopropyl betaine (CAPB), an anionic surfactant sodium lauryl sulfate (SLSS), and mixed salts (tetrasodium pyrophosphate, sodium acid pyrophosphate, sacharrin, and sodium fluoride) in sorbitol/H2O mixed solvent at different mass fraction of SLSS (XSLSS) were systematically investigated by steady and dynamic rheology, dynamic light scattering, and diffusion ordered spectroscopy (DOSY). When fixing the salt concentration and the mass ratio of sorbitol in mixed solvent (R), the zero‐shear viscosity increases first and then decreases showing a maximum with increasing XSLSS, resulting from the formation and entanglement of wormlike micelles. Especially when XSLSS is between 0.33 and 0.80, the mixture is dominated by entangled wormlike micelles coexisting with small micelles and separated wormlike micelles, and shows high viscoelasticity. The maximum of the zero‐shear viscosity is ca. 5 orders of magnitude larger than that of sorbitol/H2O mixed solvent or the CAPB/SLSS aqueous solution. The characteristic structural parameters for the micellar solutions at different XSLSS are also estimated from further analysis of the rheological results, and indicate the stronger network structures of the wormlike micelles are formed in our systems compared with the wormlike micelles formed by a traditional zwitterionic/anionic surfactant aqueous solutions. The great improvements of rheological properties are attributed to the strong screening effects of the mixed salts and the strong solvophobic effect of sorbitol on the electrostatic and hydrophobic interaction between the CAPB and SLSS molecules. The present work has improved our understanding about the aggregation behavior of zwitterionic/anionic mixed surfactants with salts in less polar solvent/H2O mixture, which would be of widely practical importance to optimize the formulation of products for personal care and household cleaning.

Section: Resultssupporting

confidence: 58%

Synergistic Behavior and Microstructure Transition in Mixture of Zwitterionic Surfactant, Anionic Surfactant, and Salts in Sorbitol/H₂O Solvent: 1. Effect of Surfactant Compositions

Tang

Wang

2017

J Surfact & Detergents

“…3. The semicircle characteristic at low frequencies reveals the systems behave as Maxwell liquids and confirms the formation of entangled wormlike micelles in solution [41,42]. The phenomenon-the experimental points deviating from the theoretical Maxwell model at high frequencies and showing an upturn of G 00 , has been found in many viscoelastic surfactant solutions, which probably results from the appearance of Rouse modes or ''breathe modes'' [43,44].…”

Section: The Effects Of Sorbitol On Rheological Behaviorsupporting

confidence: 60%

Rheological Properties and Microstructure Transition in Mixture of Zwitterionic Surfactant, Anionic Surfactant and Salts in Sorbitol/H₂O Solvent: 2. Effect of Salts and Sorbitol

Tang²,

Wang

2017

J Surfact & Detergents

The impact of mixed salts and sorbitol on the viscoelastic properties of a multi‐component system, made of a zwitterionic surfactant cocoamidopropyl betaine (CAPB), an anionic surfactant sodium lauryl sulfate (SLSS) and mixed salts (tetrasodium pyrophosphate, sodium acid pyrophosphate, saccharin and sodium fluoride) in sorbitol/H2O mixed solvent are systematically investigated by steady state and dynamic rheology. As reported previously, the viscosity of the mixed system passes through a maximum with increase in the SLSS mass fraction (XSLSS) at a fixed total surfactant concentration, salt concentration (Csalt) and mass ratio of sorbitol in mixed solvent (R). The shape of the XSLSS‐dependent viscosity curve does not change regardless of Csalt and R, but adding salts or sorbitol has different effects on the rheological properties of this system. The former due to a high screening effect plays an important role in the elongation and entanglement of the wormlike micelles, facilitating the enhancement of rheological properties and the formation of Maxwell fluids. The latter has a dual effect on the rheological properties and phase behavior of the mixtures. A certain amount of sorbitol can promote the formation entangled wormlike micelles, while the effect is reversed if the sorbitol content is too large. The electrostatic and hydrophobic interaction between CAPB and SLSS are the prerequisite for the aggregate formation and transition. Meanwhile, the aggregation behaviors are strongly influenced by the balance between low dielectric constant, strong solvophobic interaction and steric effect of sorbitol with the ability to form hydrogen bonds which favors the growth of micelles, and appearance of aqueous two‐phase systems with smaller amounts of wormlike micelles in CAPB‐rich regions which oppose enhancement of rheological properties. Our findings provide a new insight and approach to control and adjust the phase behavior of such a complicated applied multi‐component system.

“…In the general context of complex fluids, they have received considerable attention from both theoreticians and experimentalists during past decades [2][3][4][5][6]. When micelles grow and entangle with each other above a critical concentration, the aggregates behave like polymers and known as Blive polymer^ [7].…”

Section: Introductionmentioning

confidence: 99%

Nanoparticles induced micellar growth in sodium oleate wormlike micelles solutions

Li²,

Zhang³

et al. 2015

Colloid Polym Sci

The rheological behavior of anionic surfactant sodium oleate (NaOA) in the presence of inorganic salt of sodiu m c a r b o n a t e ( N a 2 C O 3 ) , o r g a n i c s a l t o f nOctyltrimethylammonium bromide (OTAB) and nano-sized silica particles (nano SiO 2 ) was studied in detail. Regardless of the surfactant concentration (NaOA), OTAB was stronger than that of Na 2 CO 3 in promoting the rapid growth of NaOA micelles, resulting in higher viscosity of NaOA aqueous solutions. It was found that nano SiO 2 nearly not affects solution viscosity in the NaOA/Na 2 CO 3 system. However, results of NaOA/OTAB system in the presence of nano SiO 2 show that nano SiO 2 promoted wormlike micelles formation and enhanced the bulk viscosity. Simultaneously, the presence of nano SiO 2 also facilitated the branched wormlike micelles formation as confirmed by viscosity and cryo-TEM measurements because of the electrostatic interactions between wormlike micelles and nano SiO 2 .