Tailoring the isothermal crystallization kinetics of isodimorphic poly (butylene succinate-ran-butylene azelate) random copolymers by changing composition

Abstract

A detailed isothermal crystallization study of biobased and biodegradable isodimorphic poly (butylene succinate-ran-butylene azelate) random copolyesters (PBS-ran-PBAz) with a wide composition range has been carried out to determine nucleation kinetics, spherulitic growth rates and overall crystallization kinetics. Differential Scanning Calorimetry (DSC) and Polarized Light Optical Microscopy (PLOM) analysis show that for the PBS-rich phase, the incorporation of BAz comonomer leads to a significant increase in nucleation density and a decrease in spherulitic growth. On the contrary, for the PBAz-rich phase, an antinucleating effect of the incorporation of BS comonomer has been observed. Both effects agree with the thermodynamic analysis of the equilibrium melting point depression as a function of composition, which predicts that only a small amount of BAz comonomer is included within the PBS-rich crystals and a larger amount of comonomer is included in PBAz-rich crystals. In addition, the enthalpy of melting of 100% crystalline PBS and PBAz were determined by a different practical approach: extrapolating real time synchrotron Wide Angle X-ray Scattering (WAXS) isothermal crystallization data and isothermal DSC data.