Synthesis and characterization of chiral polythiophenes: Poly [( R)-(−) and ( S)-(+)-2-(3′-thienyl)ethyl N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate

Abstract

( R)-(−) ( 1) and ( S)-(+)-2-(3′-Thienyl)ethyl N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate ( 2) monomers were synthesized, characterized, and polymerized in chloroform using FeCl 3 as an oxidizing agent. Molecular weights of 2.6 × 10 4 and 3.2 × 10 4 for poly1 and poly2, respectively, were determined by SEC analysis. FTIR spectra of the polymers indicated the coupling of monomers through the α positions. UV–vis spectra showed absorption bands at λ max = 226 and 423 nm for poly1 and poly2, ascribed to transitions of side groups and polythiophene backbone, respectively. Poly1 and poly2 remained stable up to 210 °C. At higher temperatures, a two step weight loss degradation process was observed for both polymers by TGA analysis. 1H NMR, in the presence of Eu(tfc) 3 , and optical rotation measurements indicate the chiral properties of the monomers 1 ([α] D 28 = −76.2) and 2 ([α] D 28 = +76.0), and the maintenance of chirality after polymerization ( poly1 [α] D 28 = −29.0 and poly2 [α] D 28 = +28.4, c = 2.5 in THF). According to scanning electron microscopic analysis, the polymers are highly porous.