Dynamic mechanical analysis of shape memory polymers: thermomechanical behavior and influence of thermal stimuli

This study explores the thermomechanical properties of polymethacrylate-based shape memory polymers (SMPs), focusing
on hot water as a thermal stimulus for shape recovery. Using differential scanning calorimetry (DSC) and dynamic mechanical
analysis (DMA), the research evaluates thermal transitions, viscoelastic behavior, and energy dissipation. DSC identified a
glass transition temperature (Tg) of 67 °C, critical for shape recovery. DMA revealed significant changes in storage modulus,
loss modulus, and energy dissipation with varying temperature and frequency. Notably, the storage modulus increased from
3.8 × 106
Pa at 10 Hz to 1 × 107
Pa at 90 Hz near Tg, validating the time–temperature superposition principle. The material
also showed asymmetric hysteresis behavior near Tg, indicating enhanced energy dissipation. Hot water at 67 °C was
highlighted as an effective external trigger, enabling reversible deformation and improved durability. Cyclic tests identified
a stability threshold, beyond which increased hysteresis and energy dissipation indicate unstable deformation. These findings
advance understanding of SMP behavior under thermal and mechanical stress and demonstrate their potential in soft
robotics, biomedical devices, and adaptive structures.