Investigation of the surfactant distribution in oil‐in‐water emulsions during the crystallization of the dispersed phase via nuclear magnetic resonance relaxometry and diffusometry

Kaysan, Gina; Kräling, R.; Meier, Manuel; Nirschl, Hermann; Guthausen, Gisela; Kind, Matthias

doi:10.1002/mrc.5305

Cited by 8 publications

(6 citation statements)

References 60 publications

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“…We were able to show in a previous work that the induction time is a function of the aqueous surfactant concentration and the relative velocity between the two collision partners [7]. Moreover, nucleation is possible because the solid particle seems to have a partial interfacial coverage with surfactant molecules compared to the fully covered interface of liquid droplets [46]. The surfactant molecules are moveable on the interface of the droplet, therefore, a molecular contact between these two partners can be given.…”

mentioning

confidence: 67%

A Microfluidic Approach to Investigate the Contact Force Needed for Successful Contact-Mediated Nucleation

Kaysan

Hirsch

Dubil

et al. 2023

Colloids and Interfaces

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Emulsions with crystalline dispersed phase fractions are becoming increasingly important in the pharmaceutical, chemical, and life science industries. They can be produced by using two-stage melt emulsification processes. The completeness of the crystallization step is of particular importance as it influences the properties, quality, and shelf life of the products. Subcooled, liquid droplets in agitated vessels may contact an already crystallized particle, leading to so-called contact-mediated nucleation (CMN). Energetically, CMN is a more favorable mechanism than spontaneous nucleation. The CMN happens regularly because melt emulsions are stirred during production and storage. It is assumed that three main factors influence the efficiency of CNM, those being collision frequency, contact time, and contact force. Not all contacts lead to successful nucleation of the liquid droplet, therefore, we used microfluidic experiments with inline measurements of the differential pressure to investigate the minimum contact force needed for successful nucleation. Numerical simulations were performed to support the experimental data obtained. We were able to show that the minimum contact force needed for CMN increases with increasing surfactant concentration in the aqueous phase.

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mentioning

confidence: 67%

A Microfluidic Approach to Investigate the Contact Force Needed for Successful Contact-Mediated Nucleation

Kaysan

Hirsch

Dubil

et al. 2023

Colloids and Interfaces

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“…Another rheological study on CNF-stabilized sesame oil Pickering emulsions showed that the locally close packing structure of oil droplets was formed, and this affected the hierarchical structures of droplets . Therefore, the ADC difference likely indicates the effects of restricted diffusion of oil within the droplets and droplet sizes/distributions and obstruction of water diffusion around the oil droplets due to oil droplet size/packing. , NMR relaxation and diffusion measurements were useful for revealing the internal and rotational mobility of surfactant molecules in the molecular-based emulsions . Therefore, further NMR/MRI studies are needed to examine the restricted effects in CNF-stabilized Pickering emulsion.…”

Section: Resultsmentioning

confidence: 99%

“…19,22 NMR relaxation and diffusion measurements were useful for revealing the internal and rotational mobility of surfactant molecules in the molecularbased emulsions. 42 Therefore, further NMR/MRI studies are needed to examine the restricted effects in CNF-stabilized Pickering emulsion.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Evaluating the Stability of Cellulose Nanofiber Pickering Emulsions Using MRI and Relaxometry

et al. 2023

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Magnetic resonance imaging (MRI) relaxometry and diffusion methods were used to highlight the instability mechanisms of oil-in-water Pickering emulsions stabilized by cellulose nanofibers (CNFs). Four different Pickering emulsions using different oils (n-dodecane and olive oil) and concentrations of CNFs (0.5 and 1.0 wt %) were systematically investigated over a period of one month after emulsification. The separation into a free oil, emulsion layer, and serum layer and the distribution of flocculated/coalesced oil droplets in several hundred micrometers were captured in MR images using fast low-angle shot (FLASH) and rapid acquisition with relaxation enhancement (RARE) sequences. The components of the Pickering emulsions (e.g., free oil, emulsion layer, oil droplets, and serum layer) were observable by different voxelwise relaxation times and apparent diffusion coefficients (ADCs) and reconstructing in the apparent T 1, T 2, and ADC maps. The mean T 1, T 2, and ADC of the free oil and serum layer corresponded well with MRI results for pure oils and water, respectively. Comparing the relaxation properties and translational diffusion coefficients of pure dodecane and olive oil obtained from NMR and MRI resulted in similar T 1 and ADC but significantly different T 2 depending on the sequence used. The diffusion coefficients of olive oil measured by NMR were much slower than dodecane. The ADC of the emulsion layer for dodecane emulsions did not correlate with the viscosity of the emulsions as the CNF concentration increased, suggesting the effects of restricted diffusion of oil/water molecules due to droplet packing.

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“…During crystallization, TW20 molecules desorb from the interface. The results of our small-angle X-Ray scattering (SAXS) measurements indicated that n-hexadecane molecules were entrapped in the center of TW20 micelles [43]. While these nanodroplets occupy a small volume, they have a very large surface area and are present in great numbers.…”

Section: Mcclements and Dunganmentioning

confidence: 90%

“…We showed in our previous study of the interfacial occupancy of liquid and solid droplets that there are fewer TW20 molecules on the surface of a crystalline n-hexadecane droplet than on a liquid droplet [43]. During crystallization, TW20 molecules desorb from the interface.…”

Section: Mcclements and Dunganmentioning

confidence: 96%

Increasing the Efficiency of Emulsion Crystallization in Stirred Vessels by Targeted Application of Shear and Surfactant

Kaysan,

Elmlinger,

Kind

2023

Colloids and Interfaces

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Emulsions containing crystalline dispersed phases hold significant importance in pharmaceutical, chemical, and life science industries. The industrial agitation and storage of these emulsions can prompt crystallization effects within the flow field, intersecting with the primary nucleation mechanisms. Notably, contact-mediated nucleation, in which subcooled droplets crystallize upon contact with a crystalline particle, and shear-induced crystallization due to droplet deformation, are both conceivable phenomena. This study delves into the crystallization processes of emulsions in a 1 L stirred vessel, integrating an ultrasonic probe to monitor droplet crystallization progression. By scrutinizing the influence of the flow field and of the emulsifiers stabilizing the droplets, our investigation unveils the direct impact of enhanced rotational speed on accelerating the crystallization rate, correlating with increased energy input. Furthermore, the concentration of emulsifiers is observed to positively affect the crystallization process. Significantly, this pioneering investigation marks the first evaluation of emulsion crystallization considering the overlapping nucleation mechanisms seen in industrial production of melt emulsions. The findings offer valuable insights for more systematic control strategies in emulsion crystallization processes, promising more efficient and sustainable industrial practices by enabling targeted application of shear and surfactants.

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Investigation of the surfactant distribution in oil‐in‐water emulsions during the crystallization of the dispersed phase via nuclear magnetic resonance relaxometry and diffusometry

Cited by 8 publications

References 60 publications

A Microfluidic Approach to Investigate the Contact Force Needed for Successful Contact-Mediated Nucleation

A Microfluidic Approach to Investigate the Contact Force Needed for Successful Contact-Mediated Nucleation

Evaluating the Stability of Cellulose Nanofiber Pickering Emulsions Using MRI and Relaxometry

Increasing the Efficiency of Emulsion Crystallization in Stirred Vessels by Targeted Application of Shear and Surfactant

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