Maleic Acid–alt–Styrene Copolymer as Compatibilizer for Poly(Ethylene Oxide)-Poly(Styrene)Blends

Abstract

Maleic acid-alt-styrene (MAaS) copolymer with number-average molecular weight [Mbar] _n = 2500 was used as a compatibilizer in blends of poly(ethylene oxide) (PEO) and poly(styrene) (PS). PEO with weight-average molecular weight [Mbar] _w = 10⁵ (PEO₁₀₀) and two PS samples with [Mbar] _w = 9 × 10⁴ and 4 × 10⁵, respectively (PS₉₀ and PS₄₀₀, respectively) were used. A depression of the melting temperature T _m of PEO in blends containing MAaS relative to pure PEO and PEO/PS blends was observed. The melting enthalpy ΔH _m for the PEO/PS blends containing MAaS was lower than those of pure PEO and PEO/PS blends without compatibilizer. The crystallization kinetics of PEO and the blends were studied by differential scanning calorimetry (DSC) at different crystallization temperatures T _c. Flory-Huggins interaction parameters χ₁₂ for the blends were estimated. Their values are in good agreement with those obtained for similar systems and suggest that the free energy of mixing ΔG _mix should be negative. Polarized optical microscopy shows differences in the macroscopic homogeneity of the blends containing compatibilizer that could be attributed to a compatibilization process.

ACKNOWLEDGMENT

We express our thanks to Fondecyt, grants 8970011 and 2970010, for partial financial help. V. V. thanks to DIPUC for a doctoral fellowship. D. R. and A. O. express their thanks to Ca^′tedra Presidencial en Ciencias ’95 for financial support.