Investigation of the viscoelasticity in flexible pressure-sensitive composites at different temperatures and...

The viscoelasticity of flexible pressure-sensitive composites is crucial to the sensitivity and operational reliability of flexible pressure sensors across a wide temperature range. In this study, we investigate the viscoelasticity of polyamide-imide (PAI) and its composite formed by doping nickel nanowires (NiNWs) at different temperatures and interfacial interaction strengths. Elevated temperatures intensify the chain motion of PAI, leading to the deterioration of viscoelasticity. The doping of NiNWs results in anisotropic viscoelasticity of the composite. Compared with PAI, the viscoelasticity of the composite along the axial direction of NiNWs is slightly affected by the temperature. The composite exhibits significantly enhanced anti-creep and anti-relaxation properties along this direction. This is attributed to the efficient axial load transfer efficiency of NiNWs, which suppresses the migration and straightening of molecular chains. However, along the radial direction of NiNWs, the anti-creep and anti-relaxation properties deteriorate significantly with increasing temperature. Particularly, the weak interfacial interaction strength between NiNWs and PAI induces the migration and straightening of molecular chains, which render the composite susceptible to creep. As the temperature increases, the storage moduli of PAI and its composite exhibit a decreasing trend, but the doping of NiNWs improves the thermal stability of the composite. Furthermore, an appropriate increase of the interfacial interaction strength can effectively inhibit the motion of molecular chains, thus enhancing the viscoelasticity of the composite. Nevertheless, an excessively high interfacial interaction strength drives PAI molecules to adhere tightly to NiNWs, thereby generating voids and reducing both the relaxation time and storage modulus.