Temperature-dependent dynamic moduli of Parylene-C columnar microfibrous thin films

Columnar microfibrous thin films (μFTFs) of the polymer Parylene C with different microfiber inclination angles were fabricated using a physicochemical vapor deposition process whereby a collimated flux of hot monomers is obliquely directed towards a planar substrate. Each μFTF was then subjected to cyclic elastic loading in one of two orthogonal directions lying wholly in the substrate plane: either (i) normal or (ii) parallel to the morphologically significant plane of the μFTF. Dynamic storage and loss moduli were determined in the 1-80 Hz frequency range for temperatures between −40 °C and 125 °C. For all columnar μFTFs, the storage and loss moduli for normal loading did not exceed their counterparts for parallel loading. All columnar μFTFs were found to be softer than a bulk film of Parylene C. In both bulk and columnar forms, Parylene C was found to be rheologically not simple.