Creep Behavior of a Maxwell Element Type Supramolecular Polymeric System

Abstract

Creep and creep recovery behavior was investigated for a supramolecular polymeric system consisting of N,N',N"-tris(3,7-dimethyloctyl)benzene-1,3,5-tricarboxamide and n-decane. In the linear viscoelastic regime, the system shows behavior well described with a Maxwell element having a set of a relaxation time (τ) and strength (G_N). The creep behavior of the system in the linear regime is simple; after showing the instantaneous value (J(0)) equal to the steady state compliance (J_e⁰ = G_N⁻¹), creep compliance (J(t)) increases with the elapsed time (t) keeping a proportional constant identical with the reciprocal of the viscosity (η₀⁻¹= (τG_N) ⁻¹). In this regime, creep recovery (J_R(t)) reaches a constant value after showing the recoverable compliance (J_R = G_N^{− 1}). In the nonlinear regime at high shear stresses, the creep behavior is classified into two categories depending on t. In a short time region, the value of J(0) and a viscosity (η⁽⁰⁾) determined from the initial slope of J(t) decrease with increasing shear stress (σ). These mean that the system becomes harder and less viscous with increasing σ. On the other hand, the creep behavior of the system is characterized by the steady state viscosity (η_e) and J_R in the steady flow state. The η_e value decreases with increasing σ, and J_R exhibits remarkable stepwise increase at a shear rate identical with the reciprocal of τ.