Miscibility and specific interactions in blends of poly(L-lactide) with poly(vinylphenol)

This paper reports a DSC and FTIR study of blends of poly(L-lactide) (PLLA) with poly(vinylphenol) (PVPh). According to the single T-g criterion, miscibility has been found in all the compositions range for the blends obtained by solution/precipitation in a dioxane/hexane pair. However, phase separation has been observed for PVPh-rich blends obtained by solvent casting from dioxane solutions. The T-g of the blends shows negative deviation from linearity. Hydrogen bonding has been found, and the band attributed to hydrogen-bonded carbonyl groups is shifted about 18 cm(-1), suggesting relatively weak hydroxyl-ester hydrogen bonds. The equilibrium melting points of pure PLLA and different blends have been recorded, and the values of the interaction parameter x(12) = -0.42 and the interaction energy density B = -8.8 cal/cm(3) have been calculated. The negative value of the interaction parameter confirms a thermodynamically miscible blend. The value of B is similar to the value found in poly(is an element of-caprolactone) (PCL)/PVPh. This small difference between both systems is feasible because the weaker attractive interactions found in PLLA/PVPh counteract against weaker repulsive interactions, as the solubility parameter of PLLA (delta = 10.1 (cal/cm(3))(1/2)) is closer to PVPh (delta = 10.6 (cal/cm(3))(1/2)) than the solubility parameter of PCL (delta = 9.2 (cal/cm(3))(1/2)). Introduction Poly(L-lactide) (PLLA) is well known in the medical industry