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To clarify the equilibrium polymerization behavior of 1,4-dioxan-2-one, PDO, bulk polymerization was investigated with Sn(II) ethylhexanoate or triethylaluminum over a range of 60-180 °C. The thermodynamic parameters ∆H ls, ∆Sls, and ceiling temperature for the polymerization were -14.1 kJ mol -1 , -26.1 J mol -1 K -1 , and 265 °C, respectively. The parameters support the thermal instability of PPDO. The calculated thermal parameters of activation were Ea ) 71.8 kJ mol -1 , ∆Gp q ) 106.2 kJ mol -1 , ∆Hp q ) 68.5 kJ mol -1 , and ∆Sp q ) -95.7 J mol -1 K -1 at 120 °C. These parameters of activation are nearly equal to those of L-lactide. PDO and PPDO are easily polymerizable and depolymerizable materials, respectively.

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