Miscibility in the blends of poly(ethylene oxide) (PEO) with n-hexyl methacrylate-methyl methacrylate random copolymers (HMA-MMA) and 2-ethylhexyl methacrylate-MMA random copolymers (EHMA-MMA) Was evaluated using glass transition and light scattering methods. EHMA-MMA was more miscible with PEO than HMA-MMA. Both blends of PEO with HMA-MMA and EHMA-MMA showed UCST-type miscibility although homopolymer blends PEO/PMMA were predicted to be of LCST-type. This was attributed to an increase in the exchange enthalpy with increasing HMA or EHMA composition in the random copolymer. From the copolymer composition dependence of miscibility the segmental x parameters of HMA/MMA, EHMA/MMA, EO/HMA and EO/EHMA were estimated using the Flory-Huggins theory extended to random copolymer systems. Miscibility in the blends of branched PEO with HMA-MMA whose HMA copolymer composition was 0.16 was compared with that in the linear PEO blends. The former blends were more miscible with HMA-MMA than the latter one by about 35 degrees C at the Maximum Cloud point temperature. (c) 2005 Elsevier Ltd. All rights reserved.