Structure-Property-Processing Relationships for Electrospun poly(3-hexylthiophene) Fibers

The electrospinning technique is an attractive route to improve the electrical properties of conjugated polymer fibers as the stretching during the electrospinning process induces the alignment of polymer chains. The effects of various processing conditions on the structure and properties of electrospun poly(3-hexylthiophene) (P3HT) fibers will be presented. The processing of P3HT was facilitated using a high molecular weight poly(ethylene oxide) (PEO). The PEO concentration in the P3HT/PEO fibers was varied from 25% to 2.5%. The molecular weight of P3HT in the P3HT/PEO fiber was also varied from »31 kg/mol to »83 kg/mol. The effect of the aging of P3HT/PEO solution on the spinnability and electrical properties was investigated. The self-assembly of P3HT in the spinning solutions was investigated using shear-rheology. The electrospun fibers display a redshift in the photoluminescence spectra compared to the corresponding thin film. This indicates more ordered chain formation in the fiber mat. The XRD data of the electrospun fibers indicate that the P3HT chains formed crystalline domains with both interchain π-π and lamellar stackings. Electrical conductivity was measured both for fibers mat and single fiber. The single fiber electrical conductivity was higher than that of the mat. An increase in electrical conductivity for the single fiber was observed with the aging of the spinning solution. The average electrical conductivity of ~1.4*10^-5 S/cm was observed in undoped fibers obtained from 24 h aged solution of P3HT with a molecular weight of 83 kg/mol. Our results provide insights into processing-structure-property relationships for conjugated polymers.