Axial correlation lengths for aromatic copolyesters

Abstract

AbstractX‐ray methods were used to investigate the structure of Vectra® and Xydar® polyesters. Xydar® is based on the aromatic polyester prepared from p‐hydroxybenzoic acid (HBA), terephthalic acid, and biphenol. Vectra® consists of HBA and 2‐hydroxy‐6‐naphthoic acid. X‐ray fiber diagrams of these materials consist of a series of nonperiodic layer lines, which are consistent with a structure consisting of parallel chains of a random comonomer sequence. The meridional peak positions are predicted accurately for fully extended, infinite chains, and the observed and calculated intensities are also in reasonably good agreement. However, there is a less adequate match between the observed and calculated peak profiles, which are predicted to be much sharper than those observed. The latter agreement is improved with a model consisting of finite chain segments with a slightly nonlinear (sinuous) conformation. The best agreement for the observed peak profiles is obtained with an ordered segment length of 90 ± 6 Å and a sinuosity of g = 3.67 ± 0.08% for Vectra® fibers and with an ordered segment length of 104 ± 6 Å and a sinuosity of g = 3.33 ±0.08% for Xydar® fibers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1839–1847, 2001