SUMMARY:A rare miscible polyacrylonitrile (PAN) blend system is reported. PAN is miscible with poly(pvinylphenol) (PVPh) as shown by thermal and spectroscopic studies. A single glass transition temperature was found in each blend. Infrared spectroscopic studies showed that the hydroxyl band of PVPh and the cyano band of PAN shifted to lower frequencies upon blending, showing the existence of specific interactions between the two polymers. The involvement of cyano groups in specific interactions was further evidenced by the development of a high-binding-energy N1s peak in each blend from X-ray photoelectron spectroscopic studies.

PDMA) in T H F solutions. However, PCYEMA does not form complexes with PDMA in T H F solutions, but the THF-cast blends are miscible over the entire composition range. Both PCYMMA and PCYEMA do not form complexes with poly(2-ethyl-2-oxazoline) (PEOx) in T H F solutions and are only miscible with PEOx when the blend contains greater than 60 wt % PCYMMA or 80 wt % PCYEMA. On the other hand, both PCYMMA and PCYEMA do not form complexes with PMVAc, PVP, or PDMA in N,N-dimethylformamide (DMF) solutions. The compositions of the complexes consist of simple mole ratios of the component polymers, and the glass-transition temperatures of the complexes are higher than those of the DMF-cast blends of similar compositions. Fourier-transform infrared spectroscopy provides further evidence on the miscibility behavior through changes in the amide carbonyl absorption bands of each tertiary amide polymer in the blends as well as in the cyano absorption band of PCYEMA. 0

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The ionization constants of nine amphoteric 5-pyridylmethylenehydantoins were measured in 80% (w/w) dimethyl sulphoxide-water at 25°C. The effects of structure and Z / E configuration on both p C and p c ' values are discussed. The especially low basicity and acidity of the Z-isomers of the N-unsubstituted and 3-methyl-substituted 5-(2-pyridylmethylene)hydantoin are attributed to the formation of intramolecular N(l)-H ... N hydrogen bond in the s-cis conformation of these compounds. The existence of N(l)-CH3...N attraction is also postulated for the Z-isomer of l-methyl-5-(2-pyridylmethylene)hydantoin. RESULTS AND DISCUSSIONCompounds 1-9 were prepared by condensation of hydantoin, 3-methylhydantoin or 1-methylhydantoin with 2-, 3or 4-pyridinecarboxaldehyde. Compounds 1-6 were obtained only in the Z-form and 7-9 in both Eand Z-isomeric forms. ' For each compound, two pK values were determined by spectrophotometric methods 0894-3230/90/ 110703-08$05.00 0 1990 by John Wiley & Sons, Ltd. 0 R' 2 -i s o m e r R' RZ H H H Me Me Me H H H Scheme 1 R t -N z3 f ' H \ 0 2-N\ R' E -i s o m e r R 3

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