TDNMR characterization of a model crystallizing surfactant system

Street, Carrie B.; Wagner, Norman J.; Vethamuthu, Martin Swanson; Hermanson, Kevin D.; Ananthapadmanabhan, K.P.

doi:10.1016/j.colsurfa.2012.04.042

Cited by 4 publications

(7 citation statements)

References 46 publications

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“…The microstructural change was characterized by X-ray scattering, DSC and PLM. We further support our experimental observations with composition calculations derived from recent TDNMR measurements of crystal content of formulations containing 12 wt% surfactant with different amounts of palmitic acid [19].…”

Section: Resultssupporting

confidence: 88%

“…DSC measurements on crystals separated from the formulation confirmed that the crystals are comprised of palmitic acid [18]. Recent TDNMR measurements led to the hypothesis that these palmitic acid crystals are surrounded by adsorbed layers of hydrated surfactants [19]. X-ray scattering, DSC and polarized light microscopy (PLM) also confirmed the presence of a surfactant-palmitic acid mixed lamellar mesophase in conjunction with crystals [18].…”

mentioning

confidence: 85%

“…Calculations based on recent TDNMR measurements of the solid content of 12 wt% surfactant formulations provide insight into the stability of the 6 wt% surfactant formulations [19]. The measurements show that approximately 2 wt% (based on the total weight) of the palmitic acid resides in the lamellar gel phase for the 12 wt% surfactant formulations.…”

Section: Tdnmrmentioning

confidence: 99%

“…TDNMR measurements were performed on formulations of 12 wt% surfactant with varying palmitic acid content. The procedure for measurements is described in detail elsewhere [19]. Calculations based on equilibrium solids content were used to estimate the amounts of immobile surfactant surrounding the palmitic acid crystals in the formulations.…”

Section: Time Domain Nuclear Magnetic Resonance (Tdnmr)mentioning

confidence: 99%

“…The samples were left in this water bath for 7 days. Digital pictures of the samples in bright field and cross-polarized light were collected to determine the solubility of palmitic acid (supplementary material for [19]). Samples that were mostly clear indicated solubilization of palmitic acid; crystals were apparent in the samples where the amount of palmitic acid exceeded the solubility.…”

Section: Solubilitymentioning

confidence: 99%

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Influence of Surfactants on the Rheology and Stability of Crystallizing Fatty Acid Pastes

Thareja

Golematis

Street

et al. 2012

J Americ Oil Chem Soc

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Complex fluids containing crystallizing fatty acids are important for consumer care products. The key features of these materials are their ability to support their weight under gravity due to the formation of a fatty acid crystal network, and to yield or flow beyond a critical applied strain. In model formulations comprised of two synthetic surfactants and a fatty acid in water, we have shown that the fatty acid crystal network consists of crystal aggregates linked by a non-crystallized mixed fatty acidsurfactant mesophase. We hypothesize that this mixed surfactant-fatty acid mesophase is critical for the macroscopic stability of the formulations. Rheological measurements combined with differential scanning calorimetry (DSC), X-ray scattering, and polarized light microscopy (PLM) measurements show the importance of surfactant loading on the overall stability of the formulations by linking morphology to rheology. Macroscopically homogeneous formulations are realized with 7-10 wt% of fatty acid. Increasing the fatty acid content without adding surfactant leads to inhomogeneous, phase separating formulations. Although both stable and unstable formulations show the presence of a surfactant-fatty acid mixed phase, a critical loading of surfactants is found to be necessary to create macroscopically homogenous formulations. We demonstrate how the rheology, microstructure and the macroscopic stability can be tuned by varying the relative amounts of surfactants and fatty acid.

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Section: Resultssupporting

confidence: 88%

mentioning

confidence: 85%

Section: Tdnmrmentioning

confidence: 99%

Section: Time Domain Nuclear Magnetic Resonance (Tdnmr)mentioning

confidence: 99%

Section: Solubilitymentioning

confidence: 99%

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