Helical and sheet structures in the nylon 4 derivatives poly (α‐benzyl‐L‐glutamate) and poly‐(α‐methyl‐L‐glutamate)

Abstract

AbstractWe have synthesized and characterized the two stereoregular title compounds with a chemical formula:magnified imageThey form helical structures, similar to α‐helices (Form II), which are rather stable, in spite of the lower density of hydrogen bonds when compared with the standard α‐helix, found in proteins. We have determined the helical parameters of these structures by X‐ ray diffraction, and electron microscopy. Thin (10–40 nm) cylindrical threads are observed by the latter technique. The helix‐coil transition has been studied by proton NMR in the system chloroform/dichloroacetic acid. In the case of poly (α‐benzyl‐L‐glutamate) we have also found a sheet structure (Form I), similar to the extended sheets found in polyamides. The benzyl rings in the side chains appear to be stacked between such sheets.