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

Abstract

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 temperature (Tgs) of the two component polymers. The Tg 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. Morover, the cold crystallization process of the PLLA component is also affected significantly by the addition of PVPh.