Synthesis and characterization of poly[(R)-(−) and (S)-(+)-3-(1′-pyrrolyl)propyl-N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate]s as chiral oligomers of pyrrole

Chiral polypyrrole oligomers were prepared from (R)-(−) (1) and (S)-(+)-3-(1′-pyrrolyl)propyl-N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate (2) by oxidative polymerization in the presence of FeCl3 as an oxidant. The new polymers were characterized by 1H NMR, FTIR and UV-vis (λmáx = 251 nm). TGA analyses of the corresponding polymers, poly1 and poly2, demonstrate an excellent thermal stability up to 204 °C, followed by two consecutive weight losses at higher temperatures. Relative number-average molecular weights of about 1.4 × 103 and 2.3 × 103, for poly1 and poly2, respectively, were measured by SEC, corresponding to oligomeric chains. Specific optical rotation measurements (c 0.1, THF) for poly1 [α]D20 = −44 and poly2 ([α]D20 = +44) suggest that chirality is retained during the polymerization. Transversal section analysis of SEM images indicates the materials isolated right after the synthesis is highly porous.