Synthesis and characterization of optically active copolymers of acenaphthylene. 2. Chiroptical and fluorescence properties

Abstract

Chiroptical and fluorescence emission properties of optically active copolymers of acenaphthylene (1) with (-)-menthyl acrylate ( 2) and (-)-menthyl methacrylate (3) have been investigated and interpreted in terms of copolymer sequence length and distribution as well as of configurational and conformational arrangement. The copolymers with 3 are characterized by a marked induced optical activity in the aromatic counits, and the dichroic absorption coefficient exhibits a maximum value at approximately 50 mol % composition. Surprisingly, no appreciable chiroptical induction was detected in copolymers of 1 with 2. Fluorescence emission spectra of all copolymers display both monomer and excimer emission, whose relative intensity strongly depends on chemical composition. A maximum value of the excimer to monomer intensity ratio was observed in the poly(l-co-S) system at 80 mol % content of 1 units, whereas a monotonic trend was shown by poly(l-co-2) samples. Fluorescence polarization measurements indicate for all the copolymers, and even for the model compound acenaphthene (4), extensive depolarization. The statistical treatment proposed by some authors for acenaphthylene-containing polymers appears therefore not to be applicable and the extent and mechanism of energy transfer in such systems remain to be better established.

Optically active polymers containing side-chain trans-stilbene chromophores directly bound to the backbone: synthesis and characterization of copolymers of (-)-menthyl acrylate with trans-4-vinylstilbene

“…Analogous results have been reported in the case of optically active copolymers of MtA with p-vinyltrifluoroacetophenone,25 of 9-vinylcarbazole with (-)-menthyl vinyl ether,18 (-)-menthyl methacrylate (MtMA),21 and MtA,21 and of acenaphthylene with MtMA. 29 In such systems this behavior was tentatively attributed to the overlapping of two opposite contributions:…”