Cold crystallization and polymorphism in an oligo(aryl ether ketone)

✍ Scribed by Daniel R. Rueda; Mikhail G. Zolotukhin

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 764 KB
• Volume: 198
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.1997.021981116

✦ Synopsis

1,3-Bis(4-phenoxybenzoyl)benzene (1) was crystallized from the glassy state at different temperatures, T,, above the glass transition temperature (Tg = 24°C). Analysis of Xray diffractograms and DSC thermograms revealed a new polymorphism: a one-dimensional order phase (GI) and a new crystal phase (G2). In both cases the molecules adopt a linear extended conformation. G1 appears for 30 "C < T, < 35 "C and its structure is like that of a smectic phase A with the molecular axis normal to the layer planes. Upon thermal treatment above 35 "C G1 converts into the crystal phase G2 which shows an inproving lateral packing of the molecules upon heating. G1 and G2 show melting temperatures around 88 and 98 "C, respectively. Provided that the thermal treatment of the cold crystallizing sample is done under ambient conditions, G2 converts into the most stable crystal phase 2 (T, = 130°C). Similar thermal treatments carried out inside a DSC calorimeter under dry N2-flow are not capable of provoking the change in the molecular conformation (from a linear extended to a V-conformation) involved in the crystal phase transition of G2 to phase 2.

Recently, Gardner reported on the polymorphism observed in polyketones containing 1,3-substituted phenylene rings697). Particularly, polyketones built up with a 1 : 1 terephthalichophthalic (TD) molar ratio show a very complex thermal behaa)