The ionicity and transport properties of a series of diethylmethylamine (DEMA) based protic ionic liquids (PILs) were characterized, principally utilizing nuclear magnetic resonance (NMR) spectroscopy. PILs were formed via the protonation of DEMA by an array of acids spanning a large range of acidities. A correlation between the (1)H chemical shift of the exchangeable proton and the acidity of the acid used for the synthesis of the PIL was observed. The gas phase proton affinity of the acid was found to be a better predictor of the extent of proton transfer than the commonly used aqueous ΔpKa. Pulsed field gradient (PFG) NMR was used to determine the diffusivity of the exchangeable proton in a subset of the PILs. The exchangeable proton diffuses with the acid if the PIL is synthesized with a weak acid, and with the base if a strong acid is used. The ionicity of the PILs was characterized using the Walden analysis and by comparing to the ideal Nernst-Einstein conductivity predicted from the (1)H PFG-NMR results.

In this study, the secondary structure of the major ampullate silk from Peucetia viridans (Green Lynx) spiders is characterized by X-ray diffraction and solid-state NMR spectroscopy. From X-ray diffraction measurement, β-sheet nanocrystallites were observed and found to be highly oriented along the fiber axis, with an orientational order, fc ≈ 0.98. The size of the nanocrystallites was determined to be on average 2.5 nm × 3.3 nm × 3.8 nm. Besides a prominent nanocrystalline region, a partially oriented amorphous region was also observed with an fa ≈ 0.89. Two-dimensional 13C–13C through-space and through-bond solid-state NMR experiments were employed to elucidate structure details of P. viridans silk proteins. It reveals that β-sheet nanocrystallites constitutes 40.0 ± 1.2% of the protein and are dominated by alanine-rich repetitive motifs. Furthermore, based upon the NMR data, 18 ± 1% of alanine, 60 ± 2% glycine and 54 ± 2% serine are incorporated into helical conformations.