POLYETHYLENE GLYCOL AND RELATED SURFACTANTS AS GREEN SOLVENTS FOR CHEMICAL SYNTHESIS
Traditional solvents in chemical synthesis are typically volatile, flammable and oftentimes toxic and harmful to the environment. One of the 12 Principles of Green Chemistry consequently concerns the replacement of traditional solvents with environmentally benign ones. One potential solvent that has been evaluated as “green solvent” is polyethylene glycol (PEG). Much less evaluated as green solvents are PEG related nonionic surfactants. As solvents, these may dissolve a wide variety of substances because of their amphiphilic structure. Just like PEG, they too are environmentally benign substances because they possess low vapor pressure, are biodegradable and with respect to toxicity, there are no concerns because they are already widely used in industrial and household products. As a proof of concept, we have been able to carry out a particular Diels-Alder reaction in these surfactant media.
Very excitingly, since 2015 there is an ongoing research collaboration with the Buntkowsky group at the Technical University in Darmstadt, Germany. Their expertise is in solid-state NMR spectroscopy and thus they study systems that are solid such as catalyst materials, which often very porous materials with large surface areas. Interestingly, PEG is a glass former and thus, when frozen preserves the structure of the liquid state. Moreover, we found out, that although the PEG related surfactants form at least in part crystalline structures, there are surprisingly still molecular motions active in the frozen state. Thus, we are using solid state research to learn more about the liquid structure and dynamics of PEG and related surfactants.
This collaborative research is presently supported by German and US funding (NSF CHE1953428) and has brought about some important project outcomes. Specifically, through physical property measurements (density, viscosity, and self-diffusion coefficients, doi.org/10.1021/acs.jced.1c00759, doi.org/10.1021/acs.jced.1c00101 ) and molecular dynamics (MD) simulations (doi.org/10.1021/acs.jpcb.2c06773), very useful practical findings were made:
The mixture composition of PEG200 does not vary significantly from vendor to vendor.
The physical properties of PEGs are only dependent on the average molar mass but not the composition.
The presence of water, the main impurity of PEGs, does not alter significantly its properties.
The physical properties of PEG can be predicted from the properties of the individual oligomer components.
The components of PEG200 do not cluster together but are spread evenly throughout.
There are significant intra- and intermolecular hydrogen bonding interactions present in PEG200 that need to be carefully considered for properly modeling the oligomer components.
Broader Impacts:
The findings show that low molar weight PEGs are quite robust solvents in so far that vendor source, exact composition and water impurities have all negligible impact how PEG behaves. This should encourage synthetic and industrial chemists to use PEG as a green solvent.
A total of nine undergraduate students of diverse backgrounds were involved in the project so far, including travel to Germany to conduct research in collaboration labs, gaining valuable professional experiences as future graduate student researchers or employees.
External Funding
National Science Foundation (NSF) Research at Undergraduate Institution (RUI) #1953428, “RUI: Solvation in Bulk and Confined Polyethylene Glycol”, $116,201 for award period 05/15/2020 to 04/30/2023.
Deutsche Forschungsgemeinschaft continuation proposal of “Characterization of the Properties and Phase Behavior of nonionic surfactants confined in mesoporous silica materials employing solid state NMR techniques,” Buntkowsky, G. (Principal), Hoffmann, M. M. (Co-Principal), Gutmann, T. (Co-Principal), 358,045.00 Euro (April 1, 2019 - March 31, 2022).
Deutsche Forschungsgemeinschaft “Characterization of the Properties and Phase Behavior of nonionic surfactants confined in mesoporous silica materials employing solid state NMR techniques,” Buntkowsky, G. (Principal), Hoffmann, M. M. (Co-Principal), Gutmann, T. (Co-Principal), 257,000.00 Euro. (September 1, 2015 - August 31, 2018).
Recognition
2014 Roland Fontaine Award for Faculty-Student Scholarship, SUNY Brockport.
2011 Chancellor’s Award for Excellence in Scholarship and Creative Activity, State University of New York.
SUNY Promising Inventor Award, received on November, 4, 2004 in Albany, NY.
Solute-Solvent Interactions of 2,2,6,6-Tetramethylpiperidinyloxyl and 5-Tert-butylisophthalic Acid in Polyethylene Glycol as Observed by Measurements of Density, Viscosity, and Self-Diffusion Coefficient”, Hoffmann, Markus M; Randall, Nathaniel P.; Apak, Miray H.; Paddock, Nathaniel, A.; Gutmann, Torsten; Buntkowsky, Gerd, Journal of Solution Chemistry, 2023, https://doi.org/10.1007/s10953-023-01265-4.
“On the Behavior of the Ethylene Glycol Components of Polydisperse Polyethylene Glycol PEG200”, Hoffmann, M.M.; Too, M.D.; Nathaniel A. Paddock, N.A. Robin Horstmann, R.; Kloth, S.; Vogel, M.; Buntkowsky, G., Journal of Physical Chemistry B, 2023, Vol. 127, 1178-1196, /doi.org/10.1021/acs.jpcb.2c06773.
“A case study on the influence of hydrophilicity on the signal enhancement by dynamic nuclear polarization“, Döller, Sonja C.; Gutmann, T.; Hoffmann, M.M., Buntkowsky, G., Solid State Nuclear Magnetic Resonance, 2022, Vol. 122, 101829 (8 pages), doi.org/1016/j.ssnmr.2022.101829.
“Densities, Viscosities and Self-Diffusion Coefficients of Several Polyethylene Glycols”, Hoffmann, M.M.; Kealy, J. D.; Gutmann, T.; Buntkowsky, G., Journal of Chemical and Engineering Data, 2022, Vol. 67, 88-103, 1021/acs.jced.1c00759.
“Solid-state NMR studies of non-ionic surfactants confined in mesoporous silica”, Buntkowsky, G.; Döller, Sonja; Haro-Mares, N.; Gutmann, T.; Hoffmann, M.M., Zeitschrift für Physikalische Chemie, 2022, Vol. 236(6-8), 939-960. org/10.1515/zpch-2021-3132.
“Polyethylene Glycol as a Green Chemical Solvent”, Hoffmann, M.M, Current Opinion in Colloid &Interface Science, 2022, Vol. 57, article number 101537 (16 pages), org/10.1016/j.cocis.2021.101537.
“Deuterium NMR Studies of the Solid-Liquid Phase Transition of Octanol-d17 Confined in SBA-15”, Döller, Sonja C.; Brodrecht, M.; Haro Mares, N. B.; Breitzke, H.; Gutmann, T.; Hoffmann, M.M., Buntkowsky, G., Journal of Physical Chemistry C,2021, Vol. 125, 25155-25164, org/10.1021/acs.jpcc.1c05873.
“Densities, Viscosities and Self-Diffusion Coefficients of Ethylene Glycol Oligomers”, Hoffmann, M.M.; Horowitz, R. H.; Gutmann, T.; Buntkowsky, G., Journal of Chemical and Engineering Data, 2021, Vol. 66, 2480-2500 org/10.1021/acs.jced.1c00101.
“Density, Speed of Sound, and Refractive Index of Binary Mixtures of 2 1‑Butyl-3-methylimidazolium Thiocyanate + 2‑Alkanols (C3−C6) at 3 Different Temperatures T = (288.15-338.15) K”, Haghani, A.; Iloukhani, H; Hoffmann, M.M., Journal of Chemical and Engineering Data, 2021, Vol. 66, 1956-1969 org/10.1021/acs.jced.0c01028.
“Breakdown of the Stokes-Einstein Equation for Solutions of Water in Oil Reverse Micelles”, Hoffmann, M.M.; Too, M. D.; Vogel, M.; Gutmann, T.; Buntkowsky, G., Journal of Physical Chemistry B, 2020, Vol. 124, 9115-9125, 10.1021/acs.jpcb.0c06124.
“Microwave Assisted Surfactant-Thermal Synthesis of Metal-Organic Framework Materials”, Cory Forsyth, Tyler Taras, Adam Johnson , Jessica Zagari, Crystal Collado, Markus M. Hoffmann, Carly R. Reed, Applied Sciences, 2020, Vol. 10, 4563 (1-10), doi:10.3390/app10134563
“Direct and Indirect Dynamic Nuclear Polarization Transfer Observed in Mesoporous Materials Impregnated with Nonionic Surfactant Solutions of Polar Polarizing Agents”, Hoffmann, Markus. M.; Bothe, Sarah.; Brodrecht, Martin; Klimavicius, Vytautas; Haro-Mares, Nadia B.; Gutmann, Torsten; Buntkowsky, Gerd, Journal of Physical Chemistry C, 2020, Vol. 124, 5145-5156, 1021/acs.jpcc.9b10504.
Invited Talk: “Physicochemical Properties of Polyethylene Glycol, a Green Solvent, Markus M. Hoffmann, International Conference on Polymer Science and Engineering, Los Angeles, CA, Oct. 17-21, 2022 (hybrid conference).
Talk: “Densities, Viscosities and Self-Diffusion Coefficients of Polyethylene Glycol, a Green Solvent”, Markus M. Hoffmann, ACS Fall 2022 National Meeting – Sustainability in a Changing World, Chicago, IL, Aug. 21-25, 2022 (hybrid conference).
Talk: “Chemistry Research of Professor Hoffmann”, Markus M. Hoffmann, guest lecture outreach program, The College at Brockport, Brockport, NY, Sept. 14, 2021.
Talk: “Dynamic Nuclear Polarization Enhanced NMR Study of Nonionic Surfactant Confined in Mesoporous Materials”, Markus M. Hoffmann, Sarah Bothe, Martin Brodrecht, Vytautas Klimavicius, Nadia B. Haro-Mares, Torsten Gutmann, Gerd Buntkowsky, 2021 Virtual Spring ACS Meeting, April 5-16, 2021.
Talk: “Solutions of Water in Oil Reverse Micelles Do Not Conform to the Stokes-Einstein Equation”, Markus M. Hoffmann, Matthew Too, Michael Vogel, Torsten Gutmann, Gerd Buntkowsky, 2021 Virtual Spring ACS Meeting, April 5-16, 2021.
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