PMID- 32857077
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20200924
IS  - 1463-9084 (Electronic)
IS  - 1463-9076 (Linking)
VI  - 22
IP  - 36
DP  - 2020 Sep 23
TI  - Dielectric relaxation of deep eutectic solvent + water mixtures: structural 
      implications and application to microwave heating.
PG  - 20466-20476
LID - 10.1039/d0cp03334k [doi]
AB  - We studied the dielectric response of deep eutectic solvents (DESs) composed of 
      choline chloride (ChCl) and such hydrogen bond donors (HBDs) as glycerol 
      (glyceline) and urea (reline) mixed with water at T = 298.15 K and frequencies 
      varying from 0.05 to 89 GHz. The dielectric loss data were used to calculate 
      normalized heating rates for these systems upon electromagnetic irradiation at 
      operating frequencies of domestic (nu = 2.45 GHz) and industrial (nu = 900 MHz) 
      microwave ovens. We show that due to slow dynamics and substantial Ohmic-loss 
      contributions DES/water mixtures constitute promising solvents for microwave 
      synthesis. Their dielectric spectra can be best fit by a superposition of 
      relaxation processes assigned to the reorientation of dipolar DES components and 
      water molecules. Static permittivities were found to smoothly decrease from the 
      value of neat water (78.4) to 22.8 for glyceline and 41.2 for reline. The 
      analysis of the obtained relaxation amplitudes suggests that the studied systems 
      can be viewed as mixtures of individual choline, HBD and water dipoles without 
      pronounced dipole-dipole correlations and negligible ChCl ion pairs. However, 
      rotational motions of the dipoles are partly synchronized, leading to the 
      slow-down of 22 water molecules for glyceline and 9.2 for reline at infinite 
      dilution. At vanishing DES concentration ChCl-HBD interactions appear to be 
      negligible. Relaxation times as a function of viscosity show a break point at the 
      ChCl : HBD : H2O ratio equal to 1 : 2 : 4. This supports the suggestion of a 
      structural transition from homogeneous electrolyte solution to a 
      micro-heterogeneous mixture already discussed in the literature.
FAU - Agieienko, Vira
AU  - Agieienko V
AUID- ORCID: 0000-0002-9398-1666
AD  - Department of Physical Chemistry, A. M. Butlerov Chemical Institute, Kazan (Volga 
      Region) Federal University, 420008 Kazan, Russian Federation. 
      vera.n.ageenko@gmail.com.
FAU - Buchner, Richard
AU  - Buchner R
AUID- ORCID: 0000-0003-3029-1278
AD  - Institut fur Physikalische und Theoretische Chemie, Universitat Regensburg, 
      D-93040 Regensburg, Germany. Richard.Buchner@chemie.uni-regensburg.de.
LA  - eng
PT  - Journal Article
PL  - England
TA  - Phys Chem Chem Phys
JT  - Physical chemistry chemical physics : PCCP
JID - 100888160
SB  - IM
EDAT- 2020/08/29 06:00
MHDA- 2020/08/29 06:01
CRDT- 2020/08/29 06:00
PHST- 2020/08/29 06:00 [pubmed]
PHST- 2020/08/29 06:01 [medline]
PHST- 2020/08/29 06:00 [entrez]
AID - 10.1039/d0cp03334k [doi]
PST - ppublish
SO  - Phys Chem Chem Phys. 2020 Sep 23;22(36):20466-20476. doi: 10.1039/d0cp03334k.