COLD CRYSTALLIZATION AND POLYMORPHISM IN AN OLIGO(ARYL ETHER KETONE)

1,3-Bis(4-phenoxybenzoyl)benzene (1) was crystallized from the glassy state at different temperatures, T-c, above the glass transition tempe rature (T-g = 24 degrees C). Analysis of X-ray diffractograms and DSC thermograms revealed a new polymorphism: a one-dimensional order phase (G1) and a new crystal phase (G2). In both cases the molecules adopt a linear extended conformation. G1 appears for 30 degrees C < T-c < 35 degrees C and its structure is like that of a smectic phase A with th e molecular axis normal to the layer planes. Upon thermal treatment ab ove 35 degrees C G1 converts into the crystal phase G2 which shows an inproving lateral packing of the molecules upon heating. G1 and G2 sho w melting temperatures around 88 and 98 degrees C, respectively. Provi ded that the thermal treatment of the cold crystallizing sample is don e under ambient conditions, G2 converts into the most stable crystal p hase 2 (T-m = 130 degrees C). Similar thermal treatments carried out i nside a DSC calorimeter under dry N-2-flow are not capable of provokin g the change in the molecular conformation (from a linear extended to a V-conformation) involved in the crystal phase transition of G2 to ph ase 2.