Dynamic viscosity versus probe-reported microviscosity of aqueous mixtures of poly(ethylene glycol) |
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Authors: | Chhavi Bhanot Shruti Trivedi Arti Gupta Shubha Pandey Siddharth Pandey |
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Affiliation: | 1. Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India;2. Department of Chemistry, CMP Degree College, University of Allahabad, Allahabad 211002, India |
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Abstract: | Correlation between the dynamic viscosity (η) and the microviscosity of a hybrid green medium constituted of water and poly(ethylene glycol) (PEG) of average molar mass (200, 400, and 600) g · mol?1, respectively, is explored over the temperatures range (10 to 90) °C across the complete composition regime. The microviscosity is obtained using a fluorescence probe 1,3-bis-(1-pyrenyl)propane (BPP), which is manifested through the ratio of the monomer-to-intramolecular excimer intensities (IM/IE). Aqueous PEG mixtures are observed to behave similar to Newtonian fluids as the temperature dependence of dynamic viscosity follows Arrhenius-type behavior. Surprisingly, a simple and convenient linear dependence of ln η with wt% PEG of the mixture is established. The BPP IM/IE is observed, in general, to increase with the bulk dynamic viscosity of the mixture having >10 wt% PEG suggesting a good correlation between the bulk dynamic viscosity and BPP-reported microviscosity when the viscosity of the aqueous PEG mixture is relatively high. |
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