Large Scale Structures in Tetrahydrofuran-Water Mixture with a Trace Amount of Antioxidant Butylhydroxytoluene (BHT)

Published

July 22, 2011

Author(s)

Zhiyong Li, He Cheng, Junyu Li, Jinkun Hao, Li Zhang, Boualem Hammouda, Charles C. Han

Abstract

Due to the closed-loop phase diagram of tetrahydrofuran (THF) - water mixture, THF aqueous solution naturally exhibits concentration fluctuation near the phase boundary. Besides the fast mode induced by concentration fluctuation, the 4.5% mole fraction, THIF aqueous solution is also characterized by a slow mode. The existence of trace amount of Butylhydroxytoluene (BHT) antioxidant in commerical THF strongly influences the slow mode in 4.5% mole fraction THF aqueous solution. A core-shell structure with BHT core and a shell made from THF-rich THF-D₂O mixture was identified by the combination of dynamic laser light scattering (DLS) and small-angle neutron scattering (SANS). BHT is hydrophobic, stabilized by a THF-rich domain in THF aqueous solution, and acts as tracer to make the large scale structure (slow mode) "visible" through SANS due to its larger contrast with the solvent. In contrast, this large scale structure was almost not detectable by SANS when BHT was removed from the THF-D₂O mixture. Combined UV-vis, DLS and static light scattering (SLS) indicated that slow moving objects do exsist, and that their size almost do not change but their concentration decreases to a small but non-zero value at the infinite dilution limit. The origin of the elusive large scale structure at zero BHT concentration is still not clear, it might be associated with some hydrophobic impurities or nanobubbles[see refs. 16-19]. However, a polydisperse model of 8.5% mole fraction THF-rich THF-D₂O mixture can fit the structure with a radius of 100nm which gives the temperature dependent low q SANS profiles of 4.5% mole fraction THF aqueous solution at zero BHT concentration

Citation

Journal of Physical Chemistry B

Volume

115

Pub Type

Journals

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Keywords

Tetrahydrofuran, Antioxidant, clustering

Citation

Li, Z. , Cheng, H. , Li, J. , Hao, J. , Zhang, L. , Hammouda, B. and Han, C. (2011), Large Scale Structures in Tetrahydrofuran-Water Mixture with a Trace Amount of Antioxidant Butylhydroxytoluene (BHT), Journal of Physical Chemistry B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=908214 (Accessed May 5, 2024)