Dielectric Study on the Dynamic Heterogeneity of Binary Polymer Blends using Pressure as the Controlled Variable

最近，人们已经认识到，在几种可混溶的二元聚合物共混物中，组分聚合物的分子运动是不均匀的，例如，每个组分动力学的温度依赖性是不同的。我们认为，施加压力可以减少聚合物链段之间的距离，从而可能会导致更多的合作链段之间的运动不同的聚合物物种。这将导致动力学均匀性的增加。基于这一观点，本研究旨在阐明动态非均匀性（均匀性）的程度与压力的关系。首先，我们构建了压力在0.1 ~ 400 MPa范围内可调的介质池。其次，我们测试了压力传感器的性能。作为测试样品，我们使用单组分无定形聚合物聚（环氧丁烷），其具有平行于链轮廓的偶极矩，因此介电可观察到全局链弛豫（所谓的正常模式过程）。由此测定了简正模弛豫时间τ_n和节段弛豫时间τ_s。我们发现两种弛豫时间具有相同的压力依赖性，即log τ=log τ_0+B（P-P_0），其中τ_0是大气压下的弛豫时间，P_0和B是常数。这种类型的压力依赖性已经被一些研究人员报道。因此，我们得出的结论是，施加的压力均匀地传递到样品试样和介电测量下的压力可以做没有问题。我们研究了几个互溶共混体系在常压下的动态非均匀行为。然而，尚未获得它们的压力依赖性的系统数据。在下一步中，我们将在压力下对几个共混体系进行介电测量，并希望阐明压力与动态非均匀性程度之间的定量关系。

Recently it has been appreciated that, in several miscible binary polymer blends, the molecular motions of component polymers are heterogeneous, e.g. temperature dependences of each component dynamics are different. We think that the application of a pressure can reduce the distances between polymer segments and thus may induce more cooperative segmental motion between different polymer species. This will result in the increase of the dynamical homogeneity. Based on this view, we aim to clarify the degree of dynamic heterogeneity(homogeneity) as a function of pressure in this research project.Firstly, we constructed the dielectric cell in which the pressure can be controlled from 0.1MPa to 400MPa. Secondly, we tested the performance of the pressure cell. As a test sample we used a single component amorphous polymer, poly(buthylene oxide), which has the dipole moment parallel to the chain contour and thus global chain relaxation (so called normal mode process) is dielectrically observable. From this measurement we determined both the normal mode relaxation times τ_n and the segmental relaxation times τ_s. We found that both relaxation times have the same pressure dependence, i.e. log τ=log τ_0+b(P-P_0), where τ_0 is the relaxation time at atmospheric pressure, P_0 and b is the constant. This type of pressure dependence is already reported by several researchers. Therefore, we concluded that the applied pressure uniformly transmits to the sample specimen and dielectric measurements under the pressure can be done without problems.We studied dynamically heterogeneous behavior for several miscible blend systems under atmospheric pressure. However the systematic data for the pressure dependences of them have not yet been obtained. In the next step we are going to do dielectric measurement on several blend systems under the pressure and want to clarify the quantitative relationship between the pressure and the degree of dynamic heterogeneity.