High throughput optimization procedure to characterize vitrification kinetics

Anabella A Abate,Daniele Cangialosi,Simone Napolitano

doi:10.1016/j.tca.2021.179084

Abstract

We present VITRIFAST, a high throughput optimization procedure to characterize the vitrification kinetics based on calorimetric measurements. By analyzing the temperature dependence of specific heat capacity, the method determines the fictive temperature, Tf, and the enthalpy change during physical aging, ΔH, within only a few seconds. We tested VITRIFAST on the low molecular weight glass-former o−terphenyl (OTP) and on an archetypal glass forming polymer, polystyrene (PS), by analyzing the outcome of two classical sets of experiments. By means of fast scanning calorimetry (FSC), we characterized the vitrification kinetics in a wide range of cooling rates and the isothermal physical aging after vitrification at a given rate. In less than 3 minutes, our method could process 18 different calorimetric scans and provided values of Tf and ΔH in excellent agreement with those reported in the literature. VITRIFAST can be employed in the analysis of the temperature dependence of any type of second order derivative of free energy and represents a tremendous advance in the data analysis of calorimetric scans. The method is particularly helpful for fast scanning calorimetry users, considering the extremely large number of heat capacity scans recorded by this technique within a few minutes.

Highlights

Vitrification is a complex phenomenon ubiquitously encountered in systems where crystallization is avoided, for instance by fast cooling [1, 2]
Since the glass transition is underlined by a kink in the temperature depen cence of enthalpy, a step in the specific heat is observed in differential scanning calorimetry (DSC) [6]
In order to evaluate the robustness of the method, we tested its precision in the case of noisy calorimetric scans, obtained by adding white noise to a standard data set obtained via fast scanning calorimetry (FSC)

Summary

Introduction

Vitrification is a complex phenomenon ubiquitously encountered in systems where crystallization is avoided, for instance by fast cooling [1, 2] It entails the transformation (glass transition) from the metastable supercooled liquid into a glass, whose signature is a kink in first order thermodynamic properties (volume, enthalpy, entropy). Characterizing the glass transition and physical aging by calorimetric methods, such as differential scanning calorimetry (DSC), is widespread in the laboratory practice. This class of techniques delivers the specific heat, that is, the first derivative at constant pressure of enthalpy. High rates may result in serious non-homogeneous thermal lags throughout the sample [7,8,9], which generally prevents a precise characterization of both Tg and width of the glass transition

Methods

Results

Conclusion