Syntheses of Poly(S-benzyl D- and L-penicillamines) and Their Secondary Structures

Abstract

Poly(S-benzyl D- and L-penicillamines) were prepared from the corresponding N-carboxyanhydrides (NCA). These polymers were soluble in alkyl halides, such as chloroform and methylene dichloride, but insoluble in dichloroacetic acid (DCA) and trifluoroacetic acid (TFA). Judging from the results obtained by a study of the infrared absorption (IR) spectra and X-ray photographs, polymers are in the ω-helical structure in the solid state. The results of the optical rotatory dispersion (ORD) and the circular dichroism (CD) in chloroform suggest that these polymers have the ω-helical structure and their helical senses are reversed. By adding TFA to the chloroform solution of these polymers, both ORD and CD curves are markedly changed from the ω-helical structure to the β-structure. The intrinsic viscosity and the flotation data indicated that the polymer exists in the intermolecular β-structure in a chloroform—TFA mixture.