A Simple and Sensitive Method for an Important Physical Parameter: Reliable Measurement of Glass Transition Temperature by AIEgens

The glass transition temperature (T_g) is an important physical parameter and signifies the reversible transition process between the glassy state and the rubbery state in polymeric materials. Herein, a simple yet reliable method, denoted as ADEtect, utilizing aggregation-induced emission luminogens (AIEgens) for T_g measurement was developed. The fluorescent images of AIEgen-doped polymer films taken at different temperatures were monitored by a camera under the same settings. By using a MATLAB program, the grayscale of the selected area in each image was calculated. This value decreased steadily with increasing the temperature, and a significant change was observed at T_g. By plotting a graph of the second derivative of relative grayscale against temperature, the T_g of a polymer can be unambiguously determined from the lowest point. The present method shows performance comparable to that of conventional DSC measurement in terms of sensitivity and reliability. Besides, it can measure multiple samples in parallel, suggesting that ADEtect is a versatile technique with high commercial value and promising for high-throughput T_g measurement.