Viscoelastic effects in relaxation processes of concentration fluctuations in dynamically asymmetric polymer blends.
Viscoelastic effects in relaxation processes of concentration fluctuations in dynamically asymmetric polymer blends.
复制标题
动态不对称聚合物共混物浓度波动松弛过程中的粘弹性效应。
DOI：
10.1103/physreve.65.021806
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
M. Nagao
中科院分区：
文献类型：
--
作者：
M. Takenaka;H. Takeno;H. Hasegawa;S. Saito;T. Hashimoto;M. Nagao
采用时间分辨小角中子散射技术，研究了重量比为50-50的动态不对称共混物[氘化聚丁二烯(DPB)/聚异戊二烯（PI）]在快速压力变化下浓度波动的弛豫过程。压力变化是在共混物的单相内进行的，电池是为高压和高温下的聚合物系统设计的。发现弛豫过程中散射强度分布随波数(q)的时间变化可以用Cahn-Hilliard-Cook线性化理论近似。理论分析得出了Onsager动力学系数的q依赖关系，其特征长度xi(ve) （xi （ve）为粘弹性长度）远大于DPB或PI的旋转半径时，在q(xi)(ve)>1处的q（-2）依赖关系。估计的xi（ve）与使用Doi和Onuki理论计算的xi（ve）非常一致，该理论考虑了在浓度波动弛豫中由组成聚合物之间的动力学不对称引起的粘弹性效应。
Relaxation processes of the concentration fluctuations induced by a rapid pressure change were investigated for a dynamically asymmetric polymer blend [deuterated polybutadiene (DPB)/polyisoprene (PI)] with a composition of 50-50 by weight by using time-resolved small-angle neutron scattering. The pressure change was carried out inside the single-phase of the blend with the cell designed for polymeric systems under high pressure and temperature. Time change in the scattered intensity distribution with wave number (q) during the relaxation processes was found to be approximated by Cahn-Hilliard-Cook linearized theory. The theoretical analysis yielded the q dependence of Onsager kinetic coefficient that is characterized by the q(-2) dependence at q(xi)(ve)>1 with the characteristic length xi(ve) (with xi(ve) being the viscoelastic length) being much larger than radius of gyration of DPB or PI. The estimated xi(ve) agrees well with that calculated using the Doi and Onuki theory that takes into account the viscoelastic effects arising from the dynamical asymmetry between the component polymers in the relaxation of concentration fluctuations.