A three-dimensionally oriented texture for poly(alpha,alpha,alpha ', alpha'-tetrafluoro-p-xylylene)

Films of poly(alpha,alpha,alpha',alpha'-tetrafluoro-p-xylylene) prepared by vapor deposition polymerization are highly crystalline and have uniplanar orientation. This orientation is maintained-on drawing x 10 at 350 degrees C, when the chains become aligned parallel to the direction of draw, leadin g to a texture of three-dimensionally oriented crystals. Thirty-five X-ray reflections are resolved by controlled rotation and tilting of the drawn sp ecimen, and these can be indexed by a triclinic unit cell with dimensions a = 5.36 Angstrom, b = 5.92 Angstrom, c = 6.57 Angstrom (chain axis repeat), alpha = 97.0 degrees, beta = 63.1 degrees, and gamma = 73.1 degrees, conta ining one monomer unit. Molecular mechanics favors a trans-planar conformat ion for the -CF2-CF2 linkage which is inclined at 90 degrees to the adjacen t phenyl groups, leading to a fiber repeat that is equal to that observed. Packing analyses point to a structure in which the phenyl groups are approx imately perpendicular to the ac plane, and this gives good agreement betwee n the observed and calculated structure amplitudes (R = 0.18). The crystal structure is similar to that proposed for the alpha-form of poly(p-xylylene ), except that the chain separation along the a axis direction is increased due primarily to the presence of the fluorine atoms.