An Acrylonitrile‐Based Copolymer Gel as an NMR Alignment Medium for Extraction of Residual Dipolar Couplings of Small Molecules in Aqueous Solution

Abstract

AbstractAn NMR weakly‐aligning polymer gel has been prepared by copolymerization of acrylonitrile and 2‐acrylamide‐2‐methyl‐1‐propanesulfonic acid in the presence of 1,4‐butanediol diacrylate as a cross‐linker. The polymer readily swells in water in a large range of temperatures, although the swelling ratio is decreased in saline solutions. The swollen gel can be mechanically compressed, in a reversible way, generating anisotropy, as easily shown in 2H NMR experiments, and allowing measurement of 1DCH residual dipolar couplings (RDCs) through F1‐coupled HSQC experiments. The performance of this gel as a NMR alignment medium was evaluated in several water‐soluble organic molecules and, while it provided RDCs of proper size for sucrose and even such as small molecule as 5‐norbornen‐2‐ol, in the case of azidothymidine and cefuroxime sodium salt the strong interaction of these molecules with the gel prevented successful extraction of the RDCs.