Crystal structures of ethylene−vinyl alcohol copolymers (EVOH) with various vinyl alcohol (VA) compositions have been determined on the basis of the X-ray diffraction data measured for the uniaxially and doubly oriented sample specimens. The unit cells of EVOH with a VA content higher than 27 mol % are monoclinic of the space group P1121/m, in which the two planar-zigzag chains are statistically packed in a mode similar to that of poly(vinyl alcohol) (PVOH). With a decreasing VA content from 27 to 14 mol %, the crystal system approaches the hexagonol type. The unit cells of EVOH with a VA content below 14 mol % are orthorhombic of the space group Pnam, similar to the packing mode of orthorhombic polyethylene (PE). The crystal structure of EVOH with the VA content in the range of 14−27 mol % is the pseudohexagonal type. In this way the transformation of the unit cell structure between the PVOH type (>27 mol %) and PE type (<14 mol %) was found to occur via the appearance of a hexagonal-type structure. This transformation was supported also by the change in the infrared spectral pattern measured for a series of EVOH copolymers.

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The aggregation of an azo dye containing one trifluoromethyl and two sulphonate groups (m-FTR) in aqueous solution has been investigated by means of 19F n.m.r. and electronic absorption spectroscopy. The 19F n.m.r. signals shifted to lower magnetic field, indicating that the fluorine atoms are located outside the aromatic ring of an adjacent dye molecule in the aggregate. On the other hand, in the case of an azo dye carrying one trifluoromethyl and one sulphonate group (m-FTS), the fluorine atoms were oriented above the adjacent aromatic ring. This difference gives a different aggregate structure between m-FTR and m-FTS. The absorption spectra of m-FTR aqueous solution show a single monomer/dimer equilibrium. On the basis of the results, the aggregation constant K was determined. The value of K for m-FTR was half that for m-FTS, suggesting that the latter dye aggregates more easily than the former owing to a lower electrostatic repulsion.