The use of a single material as a multifunctional insulator (i.e. substrate, gate dielectric, and passivation layer) in the same device will reduce cost and improve the sustainability of flexible integrated circuits. Towards that goal, use of the oblique-angle physicochemical deposition technique to fabricate columnar microfibrous thin films of Parylene C and thereby lower the relative permittivity motivated the examination of these materials as interlayer dielectrics in flexible electronics. The static Young's moduli, yield strengths, and relative permittivity of columnar microfibrous thin films of Parylene C were correlated to the porosity, crystallinity, and the deposition angle. The Poole-Frenkel conduction mechanism is responsible for the DC leakage current at temperatures not exceeding 100°C, and the AC leakage current is attributable to small-polaron tunneling mechanism. The leakage current after the application of a constant-voltage stress for a certain duration conforms to the Kohlrausch-Williams-Watts relaxation model, and the capacitance of a columnar microfibrous thin film will degrade by 20% in 10 years.