Enhanced properties in chemically polymerized poly(terthiophene) using vapour phase techniques

Poly(terthiophene) is an electronically conducting polymer with potential applications in solar energy devices. In the present study a series of poly(terthiophene) (PTTh) films are chemically polymerized (CP) at various temperatures and compared with a novel method of vapour phase polymerization (VPP). Utilizing the thiophene trimer (terthiophene) as the starting material, polymerization is achieved with Fe(III) tosylate. The films are characterized by their Raman and absorption spectra, in addition to differential scanning calorimetry (DSC), optical microscopy, electrochemical impedance spectroscopy (EIS) and four-point probe surface conductivity measurements. From the spectroscopy studies, increased conjugation length of the polymer chains with decreasing temperature or vapour phase polymerization is evident. More surprisingly, DSC results indicate the order of the polymer chains is dramatically enhanced by vapour phase polymerization and the D.C. conductivity is an order of magnitude higher for VPP compared with traditional CP films. Additionally, the optical micrographs reveal a significantly different morphology than the films cast from solution.