Miscibility and crystallization behaviors of poly(ethylene succinate)/poly(p-dioxanone) (PES/PPDO) blends were investigated by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). PES/PPDO blends are completely miscible as proved by the single grass transition temperature (T(g)) dependence of composition and decreasing crystallization temperature of the blends in comparison with the respective component. POM observation suggests that simultaneous crystallization of PES and PPDO components in the blends took place, spherulites of one component can crystallize inside the spherulites of the other component, and the unique interpenetrated crystalline morphology has been formed for the blends in the full composition range. Isothermal crystallization kinetics of the blends was studied by DSC and the data were analyzed by the Avrami equation. The results suggest that the crystallization mechanisms of the blends were unchanged but the overall crystallization rates were slowed down compared with neat PES and neat PPDO. WAXD results indicate that the crystal structures of PES and PPDO did not change in the blends.

Lanthanum isopropoxide (La(OiPr)3) has been synthesized and employed for ring‐opening polymerization of 1,4‐dioxan‐2‐one in bulk as a single‐component initiator. The influences of reaction conditions such as initiator concentration, reaction time, and reaction temperature on the polymerization were investigated. The kinetics indicated that the polymerization is first‐order with respect to the monomer concentration. The Mechanistic investigations according to 1H NMR spectrum analysis demonstrated that the polymerization of PDO proceeded through a coordination‐insertion mechanism with a rupture of the acyl‐oxygen bond of the monomer rather than the alkyl‐oxygen bond cleavage. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5214–5222, 2008

Novel nanocomposites based on aliphatic poly(ester-ether) [poly(p-dioxanone), PPDO] and fibrous clay (sepiolite) were successfully prepared by surface-initiated polymerization of p-dioxanone (PDO) in the presence of organo-modified sepiolite (OSEP). The existence of OSEP-grafted PPDO in nanocomposites, generated via surface-initiated polymerization from the hydroxyl group-abundant OSEP surface, greatly contributes to improving the performance of these nanocomposites. The dispersion uniformity of OSEP nanofibers in PPDO matrix was confirmed by scanning electron microscope (SEM) observations. Crystallization rate increased with increasing OSEP loading. Surprisingly, only OSEP nanofibers bundles acted as heterogeneous nucleating agents during the latter stage of PPDO crystallization. The incorporation of OSEP significantly enhanced the modulus and viscosity of nanocomposites, whereas nanocomposites still presented liquid-like behavior as neat PPDO. The exciting aspect of this research is that nanocomposites were reinforced and toughened by the addition of OSEP nanofibers.

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The ring-opening polymerization (ROP) of p-dioxanone (PDO) under microwave irradiation with triethylaluminum (AlEt 3) or tin powder as catalyst was investigated. When the ROP of PDO was catalyzed by AlEt 3 , the viscosity-average molecular weight (M v) of poly(p-dioxanone) (PPDO) reached 317,000 g mol À1 only in 30 min, and the yield of PPDO achieved 96.0% at 80 8C. Tin powder was successfully used as catalyst for synthesizing PPDO by microwave heating, and PPDO with M v of 106,000 g mol À1 was obtained at 100 8C in 210 min. Microwave heating accelerated the ROP of PDO catalyzed by AlEt 3 or tin powder, compared with the conventional heating method. V