Structure and Viscoelastic Properties of Diblock Copolymers in Disordered State

本文研究了聚苯乙烯-b-2-乙烯基吡啶及其氘代衍生物在有序-无序转变（ODT）附近的无序态的结构和粘弹性能。该样品适合于此类研究，因为两种组分具有几乎相同的物理性质，但在某些条件下仍会分离。我们取得的成果如下。(1)We通过流变仪和小角中子散射（SANS）测量确定了嵌段共聚物样品在宽范围的分子量（10 k至100万）和浓度（10%至本体）内的ODT。半稀释区的数据可以用考虑涨落效应的理论来解释。然而，半浓缩区和浓缩区之间的过渡并不清楚。(2)We发现通过动态力学分析获得的弹性参数比部件的弹性参数大几倍，但是通过稳态剪切流测量的弹性参数变得与部件的弹性参数几乎相同。这种差异不能仅仅用流变学行为来解释。有两种可能性，一种是流动诱导有序化，另一种是稳定剪切流抑制波动。(3)To为了阐明上述行为，我们在相应的条件下进行了流动-SANS测量，发现没有流动诱导的微区结构，因此我们认为上述粘弹性行为可以用稳态剪切流动下的波动效应及其抑制来解释。

We have studied structure and viscoelastic properties of poly(styrene-b-2-vinyl-pyridine)s and their deutrated counterparts in the disordered state near the order-disorder transition (ODT) both in bulk and in a common good solvent. This specimen is suitable for such study since both components have almost the same physical properties but still segregate at certain conditions. The results we have achieved are listed as follows.(1)We determined ODT for the block copolymer samples in wide ranges of molecular weight (10k to million) and concentration (10% up to bulk) by rheometry and small angle neutron scattering (SANS) measurements. The data in semidilute region could be explained by the theory which account for fluctuation effect. However, the transition between semidilute and concentrated regions was not clear.(2)We found that the elastic parameters obtained by dynamic mechanical analysis are a few times larger than those of components but the elastic parameters measured by steady shear flow become almost the same as those of components. The difference cannot be explained by rheological behavior alone. There are two possibilities ; one is flow-induced ordering and another is suppression of fluctuation by steady shear flow.(3)To clarify above behavior, we performed flow-SANS measurements at the corresponding condition and found that there is no flow-induced microdomain structure so that we concluded the above viscoelastic behavior can be explained by fluctuation effect and its suppression under steady shear flow.