Sweet Sidechain: A Glycopeptide-based Alignment Medium to Measure Residual Dipolar Couplings in Neat Acetonitrile

Abstract

Homopolyglutamates are well-known liquid crystalline polymers (LCPs) with a semi-flexible main chain. The polymeric backbone forms an α-helical secondary structure stabilized through intramolecular hydrogen bonds, making these rigid-rod-type polymers macroscopic mesogens. One important application of these homopolyglutamates is their use as lyotropic liquid crystalline (LLC) alignment media, which allows the determination of highly important anisotropic NMR observables like residual dipolar couplings (RDCs) for the structure elucidation of organic compounds. Herein, we report a novel polyglutamate bearing a per-acetylated glucose side chain, introduced by a postpolymerization modification approach via click-chemistry. The modified polymer exhibits unique properties concerning solvent compatibility, including the formation of stable LLC-phases in neat acetonitrile, which is a first of its kind for LLC-based alignment media.