Molecular Orientation in Poly-p-Xylylene Films

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Abstract
An electron diffraction study of thin (100–200 Å) vapor‐deposited films of poly‐p‐xylylene which had been annealed to the beta modification reveals that the majority of crystallites are very specifically oriented with (10·0) prism faces in the plane of the film. Since the polymer chains are aligned in the c‐axis direction [00·1], it follows that the molecules within oriented crystallites are lying in the film plane. A smaller number of crystallites are randomly oriented in these films. These conclusions are qualitatively extended on the basis of x‐ray diffraction data to include films as thick as 4 mil. This study corroborates the hexagonal assignment to the beta cell, with a=20.52 and c=6.581 Å. The level of orientation is essentially independent of the nature of the crystalline and amorphous substrates upon which the films were deposited, but is inversely proportional to the partial pressure of the p‐xylylene monomer in the vapor phase above the substrate.