The influence of morphology on the rheological properties of poly(ethylene oxide) (PEO) and natural rubber-graft-poly(methyl methacrylate) (NR-g-PMMA) blends in the melt was investigated. The blends were prepared at different blend compositions by a solution-casting method. Linear viscoelastic shear oscillations measurements were performed in order to determine the elastic and viscous properties of the blends in the melt. The rheological results suggested that the blending of the two constituents reduced the elasticity and viscosity of the blends. The addition of an even small amount of NR-g-PMMA to PEO changed the liquid-like behavior of PEO to more solid-like behavior. Morphological investigations were carried out by optical microscopy to establish the relationship between morphology and melt viscosity. Depending on the blend compositions and viscosities, either droplet–matrix or co-continuous morphologies was observed. PEO/NR-g-PMMA blends exhibited a broad co-continuity range, and phase inversion was suggested to occur at the PEO/NR-g-PMMA blend with a mass ratio of 60/40 (m/m), when NR-g-PMMA was added to PEO as a matrix.

This study presents the correlation of thermal, morphological and melt rheological properties of poly(ethylene oxide)/poly(methyl acrylate) (PEO/PMA) blends and PEO/poly(n‐butyl methacrylate) (PEO/PnBMA) blends. The miscibility and correlation of these properties were assessed through thermal analysis such as glass transition temperature (Tg) and apparent melting temperature (Tm), morphological study and melt rheological analysis of the blends. The results show that PEO/PMA blends are miscible as suggested by the number of Tg values that follow the Fox equation and the development of homogeneous mixtures in the molten state (T = 80 °C). On the other hand, PEO/PnBMA blends are immiscible as shown by the constancy of the Tg values of PEO throughout the blend compositions. The immiscibility was confirmed by optical microscopy which shows the matrix‐droplet and co‐continuous morphologies (i.e. heterogeneous mixtures) in the PEO/PnBMA blends at T = 80 °C. Melt rheological properties of the immiscible PEO/PnBMA blends are affected by the blend compositions and show significant deviation from Maxwell behaviour. Conversely, the rheological properties of the miscible PEO/PMA blends show close to Maxwell behaviour. Hence, the correlation of thermal, morphological and melt rheological studies is discussed for both miscible and immiscible PEO/polyacrylate blends. © 2023 Society of Industrial Chemistry.