The objective of this work was to study the miscibility and phase-separation temperatures of poly(styrene-co-maleic anhydride) (SMA)/poly(vinyl methyl ether) (PVME) and SMA/poly(methyl methacrylate) (PMMA) blends with differential scanning calorimetry and small-angle light scattering techniques. We focused on the effect of SMA partial imidization with aniline on the miscibility and phase-separation temperatures of these blends. The SMA imidization reaction led to a partially imidized styrene N-phenyl succinimide copolymer (SMI) with a degree of conversion of 49% and a decomposition temperature higher than that of SMA by about 20 degrees C. We observed that both SMI/PVME and SMI/PMMA blends had lower critical solution temperature behavior. The imidization of SMA increased the phase-separation temperature of the SMA/PVME blend and decreased that of the SMA/PMMA blend. (C) 2008 Wiley Periodicals, Inc.