Motions and Conformational Properties of Macromolecules in Solution

9223212施拉格这项研究是在聚合物分子在溶液中的构象动力学的一般领域。实验研究小振幅、周期性时变剪切流作用下聚合物溶液的振荡流动双折射(OFB)和粘弹性(VE)，这些条件将探索这些实验中重要的整体运动规律。一些研究将利用定制仪器在高粘度溶剂中进行宽有效频率范围的测量，这也提供重要的温度依赖信息；将使用其他提供中高频数据的仪器来在低粘度溶剂中获得宽频率覆盖范围。溶质诱导的溶剂动力学修饰、溶质浓度、温度、分子量、总的链几何构型(支化)、溶剂质量以及不同的聚合物和溶剂种类对OFB和VE性质的影响的详细实验研究将开始或继续进行，并与各种理论预测进行比较。对于不规则梳子(随机放置的支链)、随机支链和具有空间变化的流体动力相互作用的链，将对聚合物对VE和OFB性质(稀溶液)的贡献的频率依赖性进行广义珠弹簧模型计算，以评估链动力学的潜力，特别是这些技术，用于聚合物的详细支化表征。还将对稀嵌段共聚物溶液的OFB和VE性质进行实验研究和理论预测，以定量评估这种嵌段共聚物动力学实验组合的表征潜力。本研究是对聚合物在溶液中的行为进行实验和模拟相结合的研究，特别是关于溶剂对大分子运动的影响。***

9223212 Schrag This research is in the general area of conformational dynamics in polymer molecules in solution. Experimental studies of the oscillatory flow birefringence (OFB) and viscoelasticity (VE) of polymer solutions subjected to small-amplitude, periodically time- varying shear flows will be carried out under conditions that will explore the entire motional regime of importance in these experiments. Some investigations will utilize custom instrumentation for wide effective frequency range measurements in highly viscous solvents which also provide important temperature dependence information; other instruments providing moderate to high frequency data will be employed to obtain wide frequency coverage in low viscosity solvents. Detailed experimental studies of the effects of solute-induced solvent dynamics modifications, solute concentration, temperature, molecular weight, overall chain geometry (branching), solvent quality and different polymer and solvent species on OFB and VE properties will be initiated or continued, and compared with various theoretical predictions. Generalized bead-spring model calculations of the frequency dependence of the polymer contribution to VE and OFB properties (dilute solutions) will be carried out for irregular combs (randomly placed branch sites), randomly branched chains and chains with spatially varying hydrodynamic interaction to assess the potential of chain dynamics in general, and these techniques in particular, for detailed branching characterization of polymers. Experimental studies and theoretical predictions of OFB and VE properties of dilute block copolymer solutions will also be undertaken to quantitatively assess the characterization potential of this combination of dynamics experiments for block copolymers. This research is a combined experimental and modeling study of the behavior of polymers in solution, especially with respect to the influence of the solvent of the motions of the macromolecules. ***