We report on the thermal behavior of polymer blends comprising a block copolymer and random copolymers of styrene and acrylonitrile (SAN). The block copolymer constituents are epsilon-caprolactone (CL) and a carbonate. Melting as well as crystallization behavior of the blocks are strongly influenced by addition of amorphous SAN, which is miscible only with PCL block. Blends under discussion can undergo different phase changes as macro- and microphase separation and crystallization. Hence, morphology formation is controlled by different transitions and even a cooperative interplay between them. Phase behavior of the blends is discussed and correlated with results of morphological studies.