Poly(phthalazinone ether nitrile ketone)s(PPENK)modified via hydrolysis of cyano groups with NaOH was studied in order to find a hydrophilic resin applicable to heat—resistant waterborne coatings．The propeties of hydrolyzates．HPPENKa(O．5 h)

HPPENKb(1．5 h)and HPPENKc(3．5 h)

were measured by differentia lscanning calorimetry(DSC)

thermogravimetrie analysis(TGA)

contact angle(water)and solubility．The results indicated that the nitrile conversion ratio and Tgof hydrolyzates increased whereas the weight loss ratio of HPPENK decreaased as bydrolysis time was prolonged．As expected

the hydrophilicity of HPPENK was improved greatly

e.g. when CN conversion ratio was 93．82％

the water contact angles was decreased from 75．3°of PPENK to 54．4°of HPPENK．By studying the effect of the reaction co-solvents

reaction temperature and NaOH concentration on hydrolysis

the optimal synthetic technology was found to be reaction at 120℃ with 6 mol／L NaOH solution and DMAc as co-solvent．Aqueous dispersions based on three modified resins were prepared and their storable stability were listed a8 follows：HPPENKc>HPPENKb>HPPENKa．Especially

the deposition of HPPENKc dispersion was nDt found aflter more than 30 days．The structures of hydrolyzares were characterized by FT IR

1H-NMR．