A new type poly(ether-ester) based on poly(trimethylene terephthalate) as rigid segments and poly(ethylene oxide terephthalate) as soft segments was synthesized and its aging behavior were investigated. Different from other polymer, the segmented block copolymers exhibited a unique aging mechanism. That is, the degradation of mechanical property within short term annealing was due to the overgrown crystals and dramatically increased crystallinity, which was proved by field emission scanning electron microscope (FE-SEM) and differential scanning calorimetry (DSC), respectively. The deterioration in mechanical property after long term annealing was the results of both the increase in crystallinity and the decrease in molecular weight. Moreover, FE-SEM showed many interesting flower-like crystals presented on the surface of annealed sample. The flower-like crystals consist of several radialized petal-like arms and a more densely packed center, which has been seldom found in polymer bulk. Wide-angle x-ray diffraction results showed that the copolymer has the same crystal structure as PTT. Such poly(ether-ester) or its blends with other polymer could be suitable for rapid degradable products, such as package and vessel. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 411-416, 2010