Thermomechanical Behavior of Carboxylated CNT/PDMS Composite

Carbon nanotube (CNT) / polydimethylsiloxane (PDMS) composites are widely used in flexible electronics and sensors, yet the impact of heat generated during operation on their mechanical performance remains poorly understood. Here, we systematically investigated the temperature-dependent elastic modulus of properly cured carboxylated CNT (c-CNT) / PDMS composite (CP) by dynamic mechanical analysis. A critical temperature (T_c) is identified, below which the elastic modulus of CP (E_CP) remains stable, while above T_c, E_CP increases sharply following the temperature, characterized by a distinct growth rate (δ_E). It reveals that T_c is an inherent property of PDMS and corresponds to the onset of secondary crosslinking in PDMS. And the sharp increase in modulus at a temperature above T_c arises from the entropy elasticity and the accumulative crosslinking-induced increase in elastic modulus (ACIEM). c-CNT introduces strong hydrogen bonding with the PDMS matrix, effectively reducing both T_c and δ_E. This work not only gains new insight into the thermomechanical behavior of CP, but also offers guidelines for the application of PDMS-based composites under varying thermal conditions.