Digital Pixel Intensity as a Proxy for DSC Features in the Optical Thermal Analysis of Isotactic Polystyrene

The crystallization behavior of semicrystalline polymers is crucial for tailoring material properties for industrial and scientific applications, particularly when traditional methods such as differential scanning calorimetry (DSC) are precluded by cost, inaccessibility, or sample size. We investigated the potential of digitally extracted pixel intensity using Polarized Optical Microscopy (POM) as a quantitative substitute for DSC for assessing polymer melting and crystallization behaviors. Using isotactic polystyrene (iPS) as a model polymer, rigorous calibration established a correlation between illuminance and digitally extracted pixel intensity (DPI). Calibration enables real-time in situ monitoring of crystallization and melting processes. Comparative analyses of melting endotherms and crystallization exotherms obtained using DPI and DSC demonstrated a strong correlation, validating DPI as an effective thermal analysis method. This study also highlights the non-destructive nature of DPI, its morphological visualization capabilities, and its potential for integration with automated digital imaging and machine-learning techniques. These findings offer a promising pathway to accessible, cost-effective, and real-time polymer characterization, which transcends limitations of conventional calorimetry. When rigorously calibrated against illuminance, DPI can track melting and crystallization trends that correlate with DSC heat flow features. However, DPI does not measure heat flow and should be interpreted as an optical surrogate, not a calorimetric equivalent.