Clarke S M, Hotta A, Tajbakhsh A R, Terentjev E M
Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE, United Kingdom.
Phys Rev E Stat Nonlin Soft Matter Phys. 2002 Feb;65(2 Pt 1):021804. doi: 10.1103/PhysRevE.65.021804. Epub 2002 Jan 18.
We study three monodomain (single-crystal) nematic elastomer materials, all side-chain siloxane polymers with the same mesogenic groups but with different types of cross linking: (i) short flexible siloxane linkage affine to the network backbone, (ii) short flexible aliphatic cross links miscible with mesogenic side-chain groups, and (iii) long segments of main-chain nematic polymer. The dynamic mechanical response of these three systems shows a characteristically universal decrease of storage modulus and a corresponding increase of loss factor. This effect of "dynamic soft elasticity" is strongly anisotropic, depending on the nematic director orientation. We examine the important role of the average backbone chain anisotropy r(T)=l(parallel)/l(perpendicular), which is affected by the cross-linking geometry and contributes to the magnitude and frequency dependence of the dynamic anomaly, and discuss possible applications in mechanical damping and polarized acoustic technology.
我们研究了三种单畴（单晶）向列型弹性体材料，它们均为侧链硅氧烷聚合物，具有相同的介晶基团，但交联类型不同：（i）与网络主链仿射的短柔性硅氧烷键，（ii）与介晶侧链基团可混溶的短柔性脂肪族交联，以及（iii）主链向列型聚合物的长链段。这三种体系的动态力学响应表现出储能模量普遍降低以及损耗因子相应增加的特征。这种“动态软弹性”效应具有强烈的各向异性，取决于向列指向矢的取向。我们研究了平均主链链各向异性r(T)=l(平行)/l(垂直)的重要作用，它受交联几何结构影响，并对动态异常的幅度和频率依赖性有贡献，同时讨论了其在机械阻尼和极化声学技术中的可能应用。
