Optical studies of regioregular poly(3-octylthiophene)s under pressure

Regioregular poly(3-octylthiophene) was subjected to optical spectroscopy studies. Spectra were collected for different values of external, hydrostatic pressure. A decrease of optical gap is observed due to decrease of the torsion angle between the adjacent thiophene ring and the enhancement of interchain interactions between parallel polymer planes. Measurements were performed for pressure up to 0.5 GPa at room temperature. The presented spectra are compared with those for non-regioregular poly (3-octylthiophene). Better resolution of the fine structure of the spectrum and lower optical energy gap are rationalized as the effect of a higher level of crystallinity and better planarity of the regioregular system.