The morphology of symmetric diblock copolymer of epsilon-caprolactone (PCL) and trimethylene carbonate (PTMC), in blends with poly(vinyl methyl ether) (PVME) is investigated with (modulated) differential scanning calorimetry (d.s.c.), time resolved small angle (SAXS) and wide angle (WAXS) X-ray spectroscopy and optical microscopy. In the melt the crystallizable block PCL is immiscible with the amorphous PTMC block. PCL is melt miscible with PVME, whereas PTMC and PVME are immiscible. Despite the much higher molecular weight of PVME, the favourable interaction between PVME and PCL results in a microphase separated morphology with PVME residing inside the PCL domains, In the melt, PVME is for up to 20 wt%, almost homogeneously mixed with PCL. Above 20 wt%, PVME partly segregates inside the PCL domains. In all cases, PCL starts to crystallize from a microphase separated melt. During the crystallization a characteristic small angle scattering peak together with the corresponding wide angle peaks develops. The long period of the crystalline morphology increases as a function of the amount of PVME.