Spherulitic structures of poly [tetrafluoroethylene‐<i>co</i>‐(perfluoroalkyl vinyl ether)]

<jats:title>Abstract</jats:title><jats:p>Spherulitic textures of poly[tetrafluoroethylene‐<jats:italic>co</jats:italic>‐(perfluoropropyl vinyl ether)] (PFA) were examined in detail using polarized optical microscopy. The PFA consisting of random comonomer units among the tetrafluoroethylene units crystallizes as spherulites composed of lamellae, although polytetrafluoroethylene usually forms extended‐chain crystals because of the rigid nature of 13/6 helices. The spherulites obtained exhibit positive birefringence since the polymer crystal has a larger refractive index in the direction normal to the chain than that along it. These fluorocopolymers exhibit a thicker long period of at least 30 nm in small‐angle X‐ray scattering profiles than is generally the case for hydrogenated crystalline polymers. In these copolymers, we consider the formation of a switchboard‐type lamellae model according to P. J. Flory's suggestion. In addition, we find the overlooked reflections near 2θ = 8.5° based on the superlattice in wide‐angle X‐ray diffraction profiles of fluorocopolymers with high reproducibility. From this result, it was found that the lattice constant that was previously proposed is required to be refined to twice the value on the <jats:italic>a</jats:italic>‐ and <jats:italic>b</jats:italic>‐axes of the reciprocal lattice to assign all the reflection indices. Copyright © 2007 Society of Chemical Industry</jats:p>