Abstract
The crystal structure and morphology in oriented solutions of the rigid polymer poly(p-phenylene benzobisoxazole) (PBZO) in polyphosphoric acid (PPA), at different degrees of exposure to moisture, were studied by transmission electron microscopy and X-ray diffraction. Two crystal solvate forms, crystalline complexes of PBZO and PPA, were found. The form I crystal solvates exhibit several sharp equatorial reflections, whereas only a few broad reflections are observed in the form II state. All crystal solvate phases studied exhibit three-dimensional crystallinity evident in sharp off-meridional reflections. This is considered to be due to unique associations between the protonated PBZO polycations and the PPA anions. Endothermic transitions observed upon heating the crystal solvates are interpreted as dissolution of the form I crystals at about 70°C and crystal-crystal transformation of the form II crystal solvate to PBZO crystals, due to deprotonation above 300°C. A microfibrillar morphology is observed in the oriented PBZO fibre coagulated by immersion in water. Similar microfibrils, less than 10 nm in width, are already observed in the form II crystal solvate state, obtained from the oriented solution by absorption of moisture.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
