RT Journal Article
T1 Unveiling an NMR-invisible fraction of polymers in solution by saturation transfer difference
A1 Novoa Carballal, Ramón
A1 Martin-Pastor, Manuel
A1 Fernández Megía, Eduardo
K1 Diffusion
K1 Magnetic properties
K1 Polymers
K1 Quantum mechanics
K1 Saturation
AB The observation of signals in solution NMR requires nuclei with sufficiently large transverse relaxation times (T2). Otherwise, broad signals embedded in the baseline afford an invisible fraction of nuclei (IF). Based on the STD (saturation transfer difference) sequence, IF-STD is presented as a quick tool to unveil IF in the 1H NMR spectra of polymers. The saturation of a polymer in a region of the NMR spectrum with IF (very short 1H T2) results in an efficient propagation of the magnetization by spin diffusion through the network of protons to a visible–invisible interphase with larger 1H T2 (STDon). Subtracting this spectrum from one recorded without saturation (STDoff) produces a difference spectrum (STDoff-on), with the nuclei at the visible–invisible interphase, that confirms the presence of an IF. Analysis of a wide collection of polymers by IF-STD reveals IF more common than previously thought, with relevant IF figures when STD > 0.4% at 750 MHz. A fundamental property of the IF-STD experiment is that the signal is generated within a single state comprising polymer domains with different dynamics, as opposed to several states in exchange with different degrees of aggregation. Contrary to a reductionist visible–invisible dichotomy, our results confirm a continuous distribution of nuclei with diverse dynamics. Since nuclei observed (edited) by IF-STD at the visible–invisible interphase are in close spatial proximity to the IF (tunable with the saturation time), they emerge as a privileged platform from which gaining an insight into the IF itself
PB ACS Publications
SN 2161-1653
YR 2021
FD 2021
LK http://hdl.handle.net/10347/29028
UL http://hdl.handle.net/10347/29028
LA eng
NO ACS Macro Lett. 2021, 10, 1474−1479. https://doi.org/10.1021/acsmacrolett.1c00628
NO This work was supported by the Spanish Ministry of Science and Innovation (RTI2018-102212-B-I00), the Xunta de Galicia (ED431C 2018/30, and Centro singular de investigación de Galicia accreditation 2019–2022, ED431G2019/03), Axencia Galega de Innovación (IN845D 2020/09), and the European Union (European Regional Development Fund-ERDF)
DS Minerva
RD 30 abr 2026