Small angle X-ray scattering studies of poly(3-octylthiophene) and poly(3,3″-dioctyl-2,2″,5′2″-terthiophene) polymer thin films

Small angle X-ray scattering (SAXS) experimental technique is applied in obtaining the macromolecular parameters (radius of gyration R_g, radius R, specific surface area S_s and surface fractal dimension) of two polythiophene derivatives, poly(3-octylthiophene) (POTH) and poly(3,3″-dioctyl-2,2″,5′2″-terthiphene) (POTTOT) thin films. Nanosized thin films of these two polymers were prepared on glass substrate with thickness around 3.5 μm by spin coating. SAXS experiments are performed with a 18-kW rotating anode X-ray generator equipped with a Cu target. A two-dimensional proportional counter is employed to detect the scattered X-rays intensity. Analyses of SAXS data using the Guinier approximation of the radius of gyration of POTH and POTTOT particles are determined as 10.73 and 9. 99 Å, respectively. Porod approximation is used to find specific surface area of POTH and POTTOT nanostructured polymeric thin films, and they are determined as 3.61×10⁸ and 3.00×10⁸ cm ^-1, respectively. The surface fractal dimension of POTH and POTTOT thin films are calculated as 2.85 and 2.65, respectively.