Studies on the odd-even effect of methylene spacers in poly(pyromellitimide-ester)s

✍ Scribed by L. J. Francisca Mary; P. Kannan

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 190 KB
• Volume: 37
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19990615)37:12<1755::aid-pola4>3.0.co;2-w

✦ Synopsis

Three series of poly(pyromellitimide-ester)s were synthesized from various N,NЈ-bis(-hydroxyalkyl)pyromellitimides (HAPMIs) by melt condensation with dicarboxylic acids, including terephthalic acid (TPA), 4,4Ј-biphenyldicarboxylic acid (BPDA), and 4,4Ј-azobenzenedicarboxylic acid (ABDA). Polymers were characterized by elemental analysis, solubility, inherent viscosity, spectra (IR, 1 H-NMR, 13 C-NMR), and X-ray diffraction (XRD). Thermal stability and phase transition behaviour were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and hotstage optical polarized microscopy (HOPM). The d-spacings, calculated from XRD data, showed an odd-even effect with varying numbers of methylene spacers. Crystallinity of polymers decreased in the following order: azobenzene Ͼ biphenyl Ͼ phenyl polymers. Similarly, DSC-obtained melting temperatures (T m 's) showed an odd-even effect, and glass transition temperatures (T g 's) decreased with increasing numbers of methylene spacers. Thermal stability decreased as methylene chain length increased. Thermal stability of polymers occurred in the following order: phenyl Ͼ biphenyl Ͼ azobenzene polymers.