NMR studies of polydiacetylenes having alkyl chains. Molecular motions of precursor monomers and the polymers at various stages of the solid-state polymerization

Abstract

Polydiacetylenes (PDAs) are synthesized from diacetylenes or more conjugated acetylenes having long chains with specific structures by the solid-state polymerization initiated by γ-ray, UV or thermal activation. By using solid-state high-resolution 13C-NMR, we studied the molecular motions of the long alkyl chains ( n-C 14H 29) of the precursor monomers and the polymers for PDAs of a butadiyne ( 2A), an octatetrayne ( 4A), a dodecahexayne ( 6A) and a p-dibutadiynylbenzene ( 2A-Bz-2A). It is shown that the yields of the solid-state polymerization are related to the molecular motions of the precursor monomers. Since the polymers of 4A and 6A have conjugated acetylenic side chains, further reactions occurred, and the intramolecular rearrangement were also monitored by 13C-NMR. The changes of the 13C spectra of the alkyl carbons are considered in detail in this paper.