Self-organisation of semi-conducting conjugated polymers

Semi-conducting conjugated polymers are of great current interest for organic electronics and light-emitting screens. Deposited from solution they exhibit a pronounced tendency of self-organisation with their alkyl side-chains relative to the substrate. The conjugated bonding along the main chain presumably should give them a certain stiffness, yet chain folding is reported for single-molecular layers on graphite. We report on small angle x-ray scattering (SAXS) from flakes of poly(dodecyl-thiophene, showing a diffraction peak corresponding to 15 nm along the chain. Also hexyl-, octyl- and decyl-materials showed long-period signals, although less pronounced. We tentatively ascribe the observeation to regular chain folding, each average fold amounting to about 40 monomer units.