Study on Relaxation of Entanglement Network Structure with Use of Differential Dynamic Modulus as a Probe

用阴离子聚合法制备了四种单分散聚丁二烯，分子量为1.4 × 10^5-7.2 × 10^5d。样品乙烯基含量均为70%。通过对双（二甲基硅基）苯的氢硅化反应，可以在样品中引入定量的分子间交联。本研究引入轻交联（Mc/Me-7）。在大剪切变形下，uncroo- linking和交联的样品都出现了链的各向异性构象，但交联样品的纠缠密度没有变化。我们用微分动模量作为探针，观察了两种样品在大剪切变形下的缠结网络结构的变化。微分动模量可以通过在橡胶高原中部以频率下降的方式将小振荡变形叠加在大剪切变形上来测量。变形以单步和双步的方式给出。用Doi-Edwards管模型和BKZ模型对结果进行了讨论。结果表明，聚合物致密体系的非线性粘弹性与纠缠网络结构的变化有明显的对应关系，大变形下纠缠网络结构的变化是由链的各向异性和纠缠密度的降低两个因素引起的。

We have prepared four monodisperse polybutadienes (Mw = 1.4x10^5-7.2x10^5d) by anionic polymerization technique. Vinyl contents of the samples were all 70%. Quantitative interomolecular cross-link can be introduced to the samples by hydrosilation with p-bis(dimethylsilyl)-benzene. In this study, lightly cross-link (Mc/Me-7) was introduced. Under large shearing deformations, anisotropic conformation of the chain occurs in both uncroo-linked and cross-linked samples, but there is no change in entanglement density in the latter sample.We have observed the change in entanglement network structure in both samples under large shearing defotrmations with the use of differential dymnamic modulus as a probe. Differential dynamic modulus can be measured by superposed small oscillatory deformation on a large shearing deformation at a frequency falls down in the middle of the rubbery plateau. Deformations were given in a single-step and double-step fashions. The results were discussed with Doi-Edwards Tube Model and BKZ Model. It can be concluded that there is clear correspondence between nonlinear viscoelastic properties of polymer dense systems and change in entanglement network structure, and change in entanglement network structure under large deformations are due to two factors of chain anisotropy and decrease in entanglement density.