Chain Structure of Substituted Stilbene−Maleic Anhydride Alternating Copolymer Probed by Solid-State NMR

Abstract

Double-quantum heteronuclear local field solid-state NMR spectroscopy (2Q-HLF solid-state NMR) has been employed to investigate the chain structure of N,N,N',N -tetraethyl-4, 4'-diaminostilbene (TDAS) and 13 C labeled maleic anhydride (MA) alternating copolymer. The torsional angle of the H- 13 C- 13 C-H part of the anhydride ring was found to be 0°, indicating an all cis configuration of the H- 13 C- 13 C-H moiety of the anhydride ring. After hydrolysis of the anhydride groups and protonation of the amino groups, the torsional angle of the H- 13 C- 13 C-H moiety of the hydrolyzed anhydride groups appears to be 60°, indicating significant rotation of the polymer backbone. Because of the predominately cis configuration of the H- 13 C- 13 C-H part of the anhydride ring, the diethylamino phenyl groups are concentrated on the two sides of the backbone plane and the anhydride groups are in the backbone plane.