Conformational Dynamics of Block Copolymer Liquids

嵌段共聚物在广泛的材料应用中得到越来越多的应用，主要是由于嵌段之间的热力学相互作用所产生的性能。随着链长和/或相互作用强度的增加，嵌段共聚物液体经历有序-无序过渡（ODT）到微观结构状态。虽然人们对强偏析极限（即进入有序态）下的可达形态了解甚多，但对ODT附近（即弱偏析极限）的行为了解甚少。我们将使用一种强大的光学技术，振荡流双折射（OFB），来诊断和表征ODT和相关的有序跃迁。此外，大量的计算表明，嵌段共聚物的稀溶液OFB性质对不同嵌段的长度和链位非常敏感；否则这两个量很难确定。我们将探索OFB作为嵌段共聚物表征工具的潜力，并以此评估嵌段相互作用对弛豫谱的影响。最后，从溶剂动力学和溶剂质量两方面探讨了溶剂在构象动力学实验中的作用。特别是，溶剂旋转弛豫与聚合物溶液的高频粘弹性之间的显著关系将进一步研究。

Block copolymers enjoy increasing use in a wide range of materials applications, due primarily to properties derived from the thermodynamic interactions between blocks. With increasing chain length and/or interaction strength, block copolymer liquids undergo an order-disorder transition (ODT) to a microstructured state. Although much has been learned about the accessible morphologies in the strong-segregation limit, i.e., well into the ordered state, the behavior in the vicinity of the ODT, i.e., the weak-segregation limit, is much less understood. We will use a powerful optical technique, oscillatory flow birefringence (OFB), to both diagnose and characterize the ODT and associated order-order transitions. In addition, extensive calculations have shown that the dilute- solution OFB properties of block copolymers are uniquely sensitive to the lengths and chain locations of the various blocks; both quantities are otherwise difficult to determine. We will explore the potential of OFB as a characterization tool for block copolymers, and in so doing assess the effect of the block-block interaction on the relaxation spectrum. Finally, the investigation will be continued of the role of the solvent in conformational dynamics experiments such as OFB, both in terms of solvent dynamics and solvent quality. In particular, a remarkable relationship between solvent rotational relaxation and the high-frequency viscoelastic properties of polymer solutions will be examined further.