Circular dichroism and exciton effect of syndiotactic methacrylic polymers with chiral diacyl hydrazide side chain. II. Poly(methacrylic acid–Nβ (L‐(+)‐lactoyl) hydrazide)

Abstract

AbstractSyndiotactic poly(methacrylic acid hydrazide) has been condensed with L‐(+)‐lactic acid to form optically active side chains which are connected to the main chain by diacyl hydrazide moieties. A model compound was prepared in the same way from pivalic acid hydrazide. The CD spectra of polymer and model compound have been recorded in aqueous solution at different pH. In the acidic and neutral range, a strong Cotton effect is observed at 195 nm for the polymer which is not present for the model. This Cotton effect may be part of an exciton doublet, the second half of which may be located below 190 nm, the limit of the CD spectrometer employed. In the alkaline region, the diacyl hydrazide moiety is deprotonated and the polymer leads in contrast to the model to a well developed exciton effect centered around a crossover point of 241 nm. The influence of the addition of alcohols and salt on the CD spectra is studied, as well as the effect of temperature. For both the acidic to neutral range on one hand, and the alkaline region, on the other hand, ordered conformations are postulated. For the alkaline region a specific helical conformation is discussed.