Amino acid endcapped poly(p-dioxanone): synthesis and crystallization

Amino acid endcapped poly(p-dioxanone)s (APPDOs) were synthesized, using either glycine, alanine, leucine, or phenylalanine to initiate the ring-opening polymerization reaction of p-dioxanone (PDO). The structures of the APPDOs were characterized by ¹H NMR spectroscopy. The initiation of polymerization by the amino acids was demonstrated via the relation between the average molecular weight and the molar feed ratio N(PDO):N(amino acid) using GPC and capillary viscosity measurements. The nonisothermal and isothermal crystallization properties of the APPDOs were studied by DSC. The Avrami equation was suitable for analyzing the isothermal crystallization of the APPDOs; the constant k and the exponent n in this equation were calculated by plotting lg[−ln(1 − X _t )] versus lgt. The crystallization rate (as assessed by studying the parameter τ _1/2) was found to increase with average molecular weight for APPDOs with the same amino acid end-group. However, for APPDOs with different end-groups, the crystallization rate was found to decrease as the size of the end-group increases.