title: Study on the applicability of dynamic light scattering (DLS) to microemulsions including supercritical carbon dioxide-swollen micelles.
abstract: The applicability of dynamic light scattering (DLS) for the characterization of the size of supercritical carbon dioxide (sc-CO2)-swollen micelles in a polyester polyol-based multicomponent microemulsion with nonionic surfactant has been thoroughly proved for the first time in this work. Systematic experiments confirming that a hydrodynamic mode is observable in either a homodyne or a heterodyne detection scheme as well as the evaluation of the influence of the laser power applied to the slightly colored microemulsion have ensured an accurate implementation of this technique for a technically relevant system. The correlation times associated with the translational diffusion coefficient of the swollen micelles in a continuous liquid phase were measured for temperatures from (298.15 to 338.15)K at pressures of (90 and 100)bar. While there was no significant effect of pressure, it was found that the translational diffusion coefficient increases with increasing temperature as expected. We postulate this is primarily related to the effect of decreasing viscosity of the continuous phase. An estimation of the hydrodynamic diameter of the sc-CO2-swollen micelles is in good agreement with values for similar systems reported in the literature. For the derivation of absolute sizes for corresponding systems, also dynamic viscosity and refractive index data will be determined simultaneously in a currently developed closed experimental loop.
authors.affiliation: Professur für Advanced Optical Technologies - Thermophysical Properties, Department of Chemical and Biological Engineering (CBI), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Straβe 6, 91052 Erlangen, Germany; Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Straβe 6, 91052 Erlangen, Germany.
authors.forename: Shane Patrick
authors.initials: SP
authors.lastname: Cadogan
authors.affiliation: Covestro Deutschland AG, 51365 Leverkusen, Germany. Electronic address: christian.hahn@covestro.com.
authors.forename: Christian Joachim
authors.initials: CJ
authors.lastname: Hahn
authors.affiliation: Professur für Advanced Optical Technologies - Thermophysical Properties, Department of Chemical and Biological Engineering (CBI), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Straβe 6, 91052 Erlangen, Germany; Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Straβe 6, 91052 Erlangen, Germany. Electronic address: michael.rausch@fau.de.
authors.forename: Michael Heinrich
authors.initials: MH
authors.lastname: Rausch
authors.affiliation: Professur für Advanced Optical Technologies - Thermophysical Properties, Department of Chemical and Biological Engineering (CBI), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Straβe 6, 91052 Erlangen, Germany; Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Straβe 6, 91052 Erlangen, Germany. Electronic address: andreas.p.froeba@fau.de.
authors.forename: Andreas Paul
authors.initials: AP
authors.lastname: Fröba
keywords: Droplet size; Dynamic light scattering (DLS); Microemulsion; Nonionic surfactant; Polyester polyol; Principle of Supercritical Microemulsion Expansion (POSME); Supercritical carbon dioxide