¹³CNMR and ESR Studies on a Polydiacetylene Having Acetylenic Carbons in the Side Chains

K. Hayamizu, S. Okada, S. Tsuzuki, H. Matsuda, A. Masaki, and H. Nakanishi
[Bull. Chem. Soc. Jpn., Vol.67, No.2, pp.342-345, 1994]

The ¹³CNMR spin-lattice relaxation times and ESR spectra were measured for a polydiacetylene obtained by the solid-state polymerization of a tetrayne with n-C₁₄H₂₉ alkyl substituents (14-4A-14). Poly(14-4A-14) has two different side chains. One side chain contains two conjugated acetylenic bonds directly bound to the main backbone conjugated system; the other is an alkyl chain. Although the unpaired electron density of poly(14-4A-14) measured by ESR is less than that in trans-polyacetylene, paramagnetic effects may contribute to the long ¹³C relaxation times of unsaturated carbons, which provides insight concerning the pi-electron structure on the conjugated system.