Crystallization Kinetics and Thermodynamic Parameters of Poly(thioglycolide)

A great achievement has been made in designing and synthesizing closed-loop recyclable polymers, while the understanding of their fundamental thermodynamic parameters and condensed-state structures rwas limited. In this study, we investigated the thermodynamic properties and crystallization kinetics of a closed-loop chemical recycling polymer, poly(thioglycolide) (PTGC), by using differential scanning calorimetry (DSC), fast scanning chip calorimetry (FSC), and wide-angle X-ray diffraction (WAXD) techniques. Based on the results of the crystallization kinetics of PTGC with different molecular weights, the optimal crystallization temperature of PTGC was identified as 80 °C. This temperature served as a boundary to distinguish homogeneous and heterogeneous crystallization regions. Combined with the crystallinities detected by WAXD and the melting enthalpies measured by DSC of isothermally crystallized PTGC samples, the ideal value of the heat of fusion determined by extrapolating the enthalpy to 100% crystallinity was 123 ± 10 J/g irrespective of the molecular weight of PTGC. Furthermore, the equilibrium melting point of PTGC was found to be 211 ± 2 and 280 ± 2 °C using the linear and nonlinear Hoffman-Weeks extrapolation method.