Chemorheology of curing as well as the phase separation behavior of carboxyl-terminated poly(2-ethyl hexyl acylate) (CTPEHA) liquid rubber-modified epoxy mixtures have been studied by several techniques. The CTPEHA was incorporated into the epoxy matrix by a prereact method. The delay in polymerization for the modified mixtures with respect to that of the neat resin can be explained by lower reactivity of the chain extended resin and viscosity effect. The phase separation has been proved for various rubber contents and as a function of cure conditions used as well. The thermal and dynamic viscoelastic behavior of the modified matrices have been examined and compared to the unmodified epoxy matrix. Finally, flexural and impact properties have been discussed in terms of the morphological behavior for an epoxy matrix modified with various amounts of CTPEHA and for a 10 phr (phr stands for parts per hundred parts of epoxy resin) CTPEHA containing matrix cured at different temperatures. (C) 2001 Elsevier Science Ltd. All rights reserved.