The phase behavior of poly(4-vinylpridine) (P4VP)/poly(vinyl acetate-c
o-vinyl alcohol) (ACA) blends has been studied as;a function of ACA co
polymer composition. Calorimetric curves for blends of ACA ranging fro
m 23 to 53% of vinyl alcohol units show exothermal peaks above the gla
ss transition corresponding to phase separation processes. Heats of th
e mixing of about 1.5 cal/g have been obtained. A progressive breaking
of H-bonds as temperature increases is detected by IR spectroscopy. C
loud point curves obtained by optical microscopy measurements depend o
n ACA copolymer composition. The binary interaction model has been app
lied to this system from cloud point data.