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

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-C₁₄H₂₉) 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.