Polymerization of diiodoacetylenes, their structure and electrical properties

Abstract

Polydiiodoacetylenes (PDIA) were polymerized at different temperatures using TiCl 4AlEt 3 and Ti(OBu) 4AlEt 3 as catalysts. The crystallinity, concentration of unpaired spins, relaxation times, diffusion of spins, conjugations and energy gaps of the polymers were determined by X-ray diffraction, spectroscopic methods and electrical measurements. A crystalline polymer was obtained with TiCl 4AlEt 3, while with Ti(OBu) 4AlEt 3 an amorphous polymer was obtained. The concentration of unpaired spins for the crystalline sample was 6.7 × 10 20 and 5.3 × 10 20 spins/mol for the amorphous one. The energy gap for the former was 0.76 and for the latter 1.29 eV, while the electrical conductivities were 5.0×10 −6 and 3.9×10 −9 Ω −1 cm −1 respectively. The amorphous sample had no spin saturation, a lower diffusivity of spins and a lower conjugation, as compared to the crystalline PDIA. The relaxation times were measured only for the latter and were T 1 = 1.189×10 −5 s and T 2 = 0.745×10 −8 s. Both samples decomposed at 300 °C into iodine and charcoal. The stability of the PDIA against oxygen was much better as compared to polyacetylene.