Fabrication and characterization of elastomeric semiconductive thiophene polymers by peroxide crosslinking

In this study, semiconductive elastomers composed of homopolythiophene with disiloxane moieties were developed. The crosslinked molecular structure in the polythiophene elastomers was introduced by dicumyl peroxide, one of the typical peroxide crosslinking reagents. The elastomers were produced through a hot-pressing process above the melting point of the polythiophene. Stress–strain curves that included tensile tests and cycle loading–unloading tests defined the crosslinked polythiophenes as elastomers. Their electrical conductivities were evaluated by two-point measurements under nondeformation and uniaxial deformation states. The results indicated that the concentration of crosslinking reagents greatly influenced the mechanical and electrical properties of crosslinking polymers. With the addition of the crosslinking reagent in concentrations from 2.5 phr to 10.0 phr, elongation at break decreased largely from 95% to 51%, while excellent elastic recoveries were observed. In the electrical resistivity measurements, all the crosslinking polymers possessed high stability of electrical properties against elongation. We crosslinked polythiophenes with disiloxane groups in its side chains by dicumyl peroxide. The crosslinked polythiophenes maintained low glass transition temperatures and low Young’s modulus, while they emerged high elastic recoveries. Moreover, as the concentration of dicumyl peroxide increased, the crosslinked polythiophenes possessed higher elastic recoveries. We obtained completely elastic semiconductive polythiophenes.