Yuriy Y. Smolin

Enhanced charge storage of ultrathin polythiophene films within porous nanostructures.

In a single step polymerization and coating, oxidative chemical vapor deposition (oCVD) has been used to synthesize unsubstituted polythiophene. Coatings have been conformally coated within porous nanostructures of anodized aluminum oxide, titanium dioxide, and activated carbon. Significant enhancement in charge capacity has been found with ultrathin polythiophene coatings that preserve the surface area and pore space of the nanostructures. Pseudocapacitors consisting of ultrathin polythiophene coated within activated carbon yielded increases of 50 and 250% in specific and volumetric capacitance compared with bare activated carbon. Devices were stable up to the 5000 cycles tested with only a 10% decrease in capacitance.

Oxidative chemical vapor deposition of polyaniline thin films

Polyaniline (PANI) is synthesized via oxidative chemical vapor deposition (oCVD) using aniline as monomer and antimony pentachloride as oxidant. Microscopy and spectroscopy indicate that oCVD processing conditions influence the PANI film chemistry, oxidation, and doping level. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) indicate that a substrate temperature of 90 °C is needed to minimize the formation of oligomers during polymerization. Lower substrate temperatures, such as 25 °C, lead to a film that mostly includes oligomers. Increasing the oxidant flowrate to nearly match the monomer flowrate favors the deposition of PANI in the emeraldine state, and varying the oxidant flowrate can directly influence the oxidation state of PANI. Changing the reactor pressure from 700 to 35 mTorr does not have a significant effect on the deposited film chemistry, indicating that the oCVD PANI process is not concentration dependent. This work shows that oCVD can be used for depositing PANI and for effectively controlling the chemical state of PANI.