Miscibility and crystallization behaviour of poly(L-lactide)/poly(p-vinylphenol) blends

The miscibility of poly(L-lactide) (PLLA)/poly(p-vinylphenol) (PVPh) blends has been studied by differential scanning calorimetry (d.s.c.) and Fourier transform. infrared (FTi.r.) spectroscopy. PLLA/PVPh blends are partially miscible as characterized by shifts in the glass transition temperatures (T(g)s) of the two component polymers. The T-g of the PLLA-rich phase increases with increasing PVPh content, while that of the PVPh-rich phase decreases with increasing PLLA content. The apparent melting temperature of PLLA is significantly depressed with increasing PVPh content. Weak hydrogen-bonding interaction exists between the carbonyl groups of PLLA and the hydroxyl groups of PVPh as evidenced in the FTi.r. spectra. In the amorphous state, the hydrogen-bonded hydroxyl band of PVPh shifts to a higher frequency upon blending with PLLA, while the carbonyl stretching band of PLLA shifts to a lower frequency with the addition of PVPh. In addition, a new carbonyl stretching band attributed to the hydrogen-bonded carbonyl groups of PLLA is found at 1700 cm(-1). The crystallinity of PLLA in the blends displays a marked decrease with increasing PVPh content. When the PVPh content is above 40 wt%, crystallization of PLLA does not occur under isothermal conditions. Moreover, the cold crystallization process of the PLLA component is also affected significantly by the addition of PVPh. (C) 1998 Elsevier Science Ltd. All rights reserved.