TY - JOUR
T1 - Nanoscale Clustering of Alcoholic Solutes in Deep Eutectic Solvents Studied by Nuclear Magnetic Resonance and Dynamic Light Scattering
AU - Häkkinen, Riina
AU - Alshammari, Odeh
AU - Timmermann, Vanessa
AU - D'Agostino, Carmine
AU - Abbott, Andrew
PY - 2019/8/6
Y1 - 2019/8/6
N2 - It was previously shown that water distributes heterogeneously in deep eutectic solvents (DESs). The aim of this study was to see whether this behavior was common to other hydrogen bonding compounds and determine when a solute formed an emulsion or a homogeneous solution. Pulsed field gradient (PFG) and nuclear Overhauser effect (NOE) nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) are employed to probe the phase behavior of glucose, 1-pentanol, and phenol in Ethaline (ethylene glycol/choline chloride, 2:1). By comparing the measured values of self-diffusivities to those calculated assuming Stokesian behavior, it was discovered that glucose forms a homogeneous solution, whereas 1-pentanol forms a heterogeneous mixture. A change in aggregate size of 10 wt % phenol in Ethaline is observed at 313 K. Above 313 K, aggregation is enhanced, and larger aggregates are formed, suggesting that melting of phenol affects the phase behavior. {1H,1H}-NOESY NMR showed that glucose interacts strongly with Ethaline, while with 1-pentanol and phenol, this interaction is weaker. DLS experiments further indicated the heterogeneity and homogeneity. Results suggest that solid solutes that are capable of strong hydrogen bonding are soluble in DESs, whereas liquid solutes form heterogeneous nanophases because of the weaker solute-solvent interactions and density difference.
AB - It was previously shown that water distributes heterogeneously in deep eutectic solvents (DESs). The aim of this study was to see whether this behavior was common to other hydrogen bonding compounds and determine when a solute formed an emulsion or a homogeneous solution. Pulsed field gradient (PFG) and nuclear Overhauser effect (NOE) nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) are employed to probe the phase behavior of glucose, 1-pentanol, and phenol in Ethaline (ethylene glycol/choline chloride, 2:1). By comparing the measured values of self-diffusivities to those calculated assuming Stokesian behavior, it was discovered that glucose forms a homogeneous solution, whereas 1-pentanol forms a heterogeneous mixture. A change in aggregate size of 10 wt % phenol in Ethaline is observed at 313 K. Above 313 K, aggregation is enhanced, and larger aggregates are formed, suggesting that melting of phenol affects the phase behavior. {1H,1H}-NOESY NMR showed that glucose interacts strongly with Ethaline, while with 1-pentanol and phenol, this interaction is weaker. DLS experiments further indicated the heterogeneity and homogeneity. Results suggest that solid solutes that are capable of strong hydrogen bonding are soluble in DESs, whereas liquid solutes form heterogeneous nanophases because of the weaker solute-solvent interactions and density difference.
KW - aggregation
KW - DES
KW - diffusion
KW - nanoemulsion
KW - nanophase
KW - solute
UR - http://www.scopus.com/inward/record.url?scp=85071724794&partnerID=8YFLogxK
U2 - 10.1021/acssuschemeng.9b03771
DO - 10.1021/acssuschemeng.9b03771
M3 - Article
AN - SCOPUS:85071724794
SN - 2168-0485
VL - 7
SP - 15086
EP - 15092
JO - ACS Sustainable Chemistry & Engineering
JF - ACS Sustainable Chemistry & Engineering
IS - 17
ER -