Molecular Weight-Dependent Coloration and Thermal Sensitivity of Hydroxypropyl Cellulose Photonic Colloids

Abstract Hydroxypropyl cellulose (HPC) photonic colloids hold immense potential for smart thermochromic applications. However, achieving tailorable thermal-responsive performance remains a significant challenge. Herein, we systematically investigate the decisive role of molecular weight in governing the coloration behavior and thermal sensitivity of self-assembled HPC photonic colloids using three variants (L-HPC, M-HPC, and H-HPC) with comparable degrees of substitution but distinct molecular weights. Decreasing the molecular weight is shown to markedly enhance thermal sensitivity, with L-HPC achieving up to 10.4 nm/°C. Dynamic light scattering (DLS) analysis reveals that this performance discrepancy stems from a molecular weight-dependent phase-separation mechanism: heating induces a faster hydrodynamic radius (Rh) growth rate and helical pitch expansion in lower-molecular-weight HPC, yielding a steeper linear fitting slope (7.39). Leveraging these discrepancies in thermal sensitivity alongside high-fidelity patterning techniques, we successfully demonstrated dynamic multicolored graphic transitions and a highly secure, temperature-keyed information encryption platform.