Abstract
This article provides an overview of strain-induced solid mesophases in polymer fibers, melt-spun from amorphous (polycarbonate, cyclo-olefin polymer, copolyamide, polyethylene terephthalate glycol) and semi-crystalline materials (polyethylene terephthalate, poly-3-hydroxybutyrate). The discussed mesophases are made of stretched, conformationally disordered macromolecules that are highly oriented along the fiber axis, and that reveal variations in their lateral spacing. Fitting algorithms for respective wide-angle x-ray diffraction (WAXD) patterns are put forward, and are directly tested on fibers melt-drawn from amorphous as well as semi-crystalline polymers. Equatorial, meridional, off-axis and azimuthal profiles are extracted from WAXD patterns and are simultaneously fitted. Best fit parameters contain detailed structural information, and lead to simulated 2D WAXD patterns, which in turn can be used to quantify the phases that are present in the fibers. We postulate that mesophases, which lead to broad equatorial reflections in WAXD patterns, can be found in all types of drawn melt-spun polymer fibers.
Highlights
Mesophases have been identified in many polymeric materials
wide-angle x-ray diffraction (WAXD) fitting results we are discussing the structural details of mesophases and amorphous phases that we have found in monofilaments melt-spun from amorphous polymers (PC, Cyclo-olefin polymer (COP), coPA), and in the Polyethylene terephthalate glycol (PETG) core of a bicomponent PETG/PMP fiber
We present a beneficial tool (2D WAXD fitting algo rithms) to quantify all phases that are present in polymer fibers, melt-spun from either amorphous or semicrystalline polymeric materials
Summary
Mesophases have been identified in many polymeric materials. The term ‘mesomorphic’ was first introduced by Friedel in 1922 [1], in order to describe an intermediate state of matter between liquid (or amor phous) and crystalline. In i), for example, the non-crystallinity (nonexistent unit cell) of the mesophase is emphasized, as well as the orientation of molecular chains We have found this particular phase, Pnc, in many of the melt-spun polymer fibers that we are presenting in this article. This phase is made of highly oriented, aligned macromolecular chains, which reveal conformational disorder and variations in lateral spacing between the chains. One observes ringshaped isotropic scattering (amorphous), and for intermediate orienta tions, one observes an arc-shaped anisotropic equatorial scattering feature, where the equatorial position, μPnc, reflects the average lateral spacing between molecular chains, dPnc. For very high orientations, the mesophase gives rise to a pair of broad equatorial peaks in the WAXD pattern, which we could only observe in drawn semi-crystalline poly mers. Orientation) can be simultaneously derived with details about both the crystalline phase (e.g. orientation, crystal size, amount of unoriented crystals) and the amorphous phase (e.g. preferred chain spacings)
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