| 초록 |
LAOS test has been widely studied in order to understand nonlinear viscoelasticity of viscoelastic material. In this study, we studied linear and nonlinear rheological properties of linear and symmetric 3-arm star polyisoprenes (PI) from FT-rheology. In a linear regime, star-shaped PI displayed much broader relaxation mode than linear PI. It is due to effect of dynamic tube dilation (DTD). In a nonlinear regime, two different topologies could be distinguished obviously. When intrinsic nonlinearity Q0 was plotted as a function of excitation, linear PI showed only one peak corresponding to disentanglement of backbone chain while star PI showed two peaks weakly. One corresponds to relaxation process of backbone chain at lower frequency, and the other corresponds to relaxation process of the arm at higher frequency. This nonlinear behavior was quantitatively predicted using molecular stress function (MSF) model. |
