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Polymer Conformation Determination by NMR Spectroscopy: Comparative Diffusion Ordered 1H-NMR Spectroscopy of Poly(2-Ethyl-2-Oxazoline)s and Poly(Ethylene Glycol) in D2O
Monnery, B.D. Jerca, V.V. Hoogenboom, R.
Monnery, B.D.
Jerca, V.V.
Hoogenboom, R.
Publication Date
2024-08-14
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(c) 2024 The Authors. This is an Open Access article distributed under the Creative Commons CC-BY license (http://creativecommons.org/licenses/by-nc/3.0/)
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2024-06-28
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Abstract
Diffusion ordered 1H-NMR spectroscopy (DOSY) is a useful, non-destructive technique for analysing polymer hydrodynamic size and intrinsic/solution viscosity. However, to date there has been no investigation of DOSY under variable temperature conditions that allow trends in polymer conformation to be determined. Poly(2-ethyl-2-oxazoline) (P(EtOx)) is a hydrophilic polymer that has the potential to replace poly(ethylene glycol) (PEG) in biomedical applications. Applying DOSY to a series of narrow-distribution P(EtOx) revealed that the apparent hydrodynamic radii scaled with molecular weight as expected. By altering the temperature of the solution the trends in Flory-type exponents were determined, enabling the determination of the power laws related to the coil-globule conformation of linear polymers directly from NMR data. These measurements were complicated by the onset of convection currents at higher temperatures, which impose a limit to the effective measurement range of ca. 10–35 °C. It was revealed that P(EtOx) had a more expanded random coil conformation than PEG, and it trended towards θ conditions at the lower critical solution temperature. In comparison, PEG was approximately in θ-conditions at room-temperature. This shows the use, and limitations of DOSY in polymer conformation analysis, and applies it to P(EtOx), a polymer which has not been analysed in this manner before.
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Monnery BD, Jerca VV, Hoogenboom R et al (2024) Polymer Conformation Determination by NMR Spectroscopy: Comparative Diffusion Ordered 1H-NMR Spectroscopy of Poly(2-Ethyl-2-Oxazoline)s and Poly(Ethylene Glycol) in D2O. Polymer Chemistry. 15(30): 3077-3085.
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