Maleic acid-alt-styrene copolymer as compatibilizer for poly(ethylene oxide)-poly(styrene) blends

Maleic acid-alt-styrene (MAaS) copolymer with number-average molecular weig ht (M) over bar (n) = 2500 was used as a compatibilizer in blends of poly(e thylene oxide) (PEO) and poly(styrene) (PS). PEO with weight-average molecu lar weight (M) over bar (w) = 10(5) (PEO100) and two PS samples with (M) ov er bar (w) = 9 x 10(4) and 4 x 10(5), respectively (PS90 and PS400, respect ively) were used. A depression of the melting temperature T-m of PEO in ble nds containing MAaS relative to pure PEO and PEO/PS blends was observed. Th e melting enthalpy DeltaH(m) for the PEO/PS blends containing MAaS was lowe r than those of pure PEO and PEO/PS blends without compatibilizer. The crys tallization kinetics of PEO and the blends were studied by differential sca nning calorimetry (DSC) at different crystalization temperatures T-c. Flory -Huggins interaction parameters chi (12) for the blends were estimated. The ir values are in good agreement with those obtained for similar systems and suggest that the free energy of mixing DeltaG(mix) should be negative. Pol arized optical microscopy shows differences in the macroscopic homogeneity of the blends containing compatibilizer that could be attributed to a compa tibilization process.