The morphological development of crystallizable polymer blends has been investigated using optical microscopy and infrared and Raman spectroscopy. Both binary and ternary blends were studied. In each case, a crystallizable polyester, either poly(hexamethylene adipate) (PHMA) or poly(hexamethylene sebacate) (PHMS), is mixed with noncrystallizable polyether, poly(propylene glycol) (PPG). Although they possess similar chemical structures, PHMA and PHMS exhibit very different miscibility behavior. In ternary blends, an acrylate, poly(methyl methacrylate and n-butyl methacrylate) [P(MMAnBMA)], is also incorporated in the mixture. With the high spatial resolution achievable (similar to 1 mu m(2)), the composition distribution can be carried out using a micro-Raman instrument. Specific Raman features associated with polyesters have been established. For immiscible PPG/PHMA blends, the composition and distribution within PHMA-rich and PHMA-poor phases are characterized. The exact composition in each phase has been obtained by analyzing Raman data obtained. Additionally, on the basis of the measured intensity for conformation-sensitive Raman peaks, the distribution of crystallites within each phase has been characterized. The third relative immobile acrylate component is extremely effective in changing the overall blend morphology.