SINGLE-CRYSTAL X-RAY STUDIES OF AROMATIC OLIGOMERS - STRUCTURAL MODELS FOR POLYIMIDES DERIVED FROM HEXAFLUOROISOPROPYLIDENE-BRIDGED AND SULFONE-BRIDGED DIANHYDRIDES

The crystal and molecular structures of two oligomeric aromatic ether- imides PhOArN(OC)2Ar'-X-Ar'(CO)2NArOPh [X=-SO2- (4) or -C(CF3)2- (5); Ar=a 1,4- and Ar'=a 1,3,4-substituted aromatic residue] have been dete rmined by single crystal X-ray diffraction. Crystal data for 4, C40H24 N2O8S.0.25 H2O: orthorhombic, Pbnm; a = 5.628(1), b = 24.903(8), c = 4 7.175(17) angstrom. Crystal data for 5, C43H24F6N2O6: monoclinic, P2(1 )/c, a = 6.919(1), b = 11.977(2), c = 43.203(9) angstrom; beta = 94.23 (2)-degrees. Molecules of the sulfone-bridged oligomer 4 pack in discr ete chevron-like lamellae, within which complementary, parallel ring-s tacking (approximately 3.5 angstrom interplanar separation) occurs bet ween aminophenol (-NC6H4O-) and arene-imide [-Ar(CO)2NAr'-] residues. In contrast, the hexafluoroisopropylidene-bridged oligomer 5 packs in a linearly displaced, non-lamellar fashion in the crystal, the structu re showing no evidence for adjacent stacking of electronically complem entary molecular sub-units.