Viscoelastic properties of physically crosslinked networks. II: Dynamic mechanical moduli (Q1199370)

[For part I, see the foregoing entry.] The paper examines the linear response to oscillatory deformations of shear and elongation types in a model transient network made up of uniform polymer chains reversibly crosslinked by associating end groups. The dynamic mechanical moduli are obtained in the untangled regime as functions of the frequency \(\omega\) and the chain breakage rate \(\beta(r)\) which itself is related to the temperature \(T\), molecular weight \(M\) and the life time \(\tau_ x\) of the bond duration. It is seen from the modulus-frequency master-curves that their dependence on the molecular weight is weak, but that on the breakage rate \(\beta(r)\) is sensitive. There is a certain temperature range, in which the network exhibits rubber-like elasticity of covalently crosslinked elastometers. Comparison of the frequency dependence of the linear viscosity \(\eta(\omega)\) with the shear rate dependence of the nonlinear stationary viscosity \(\eta_{st}(\dot\gamma)\) shows, that at high frequencies \(\eta(\omega)<\eta_{st}(\dot\gamma)\), which indicates that the Cox-Merz rule does not hold in physically crosslinked networks.