Motions and Conformational Properties of Macromolecules in Solution

[2223212] Schrag这项研究是在溶液中聚合物分子构象动力学的一般领域。实验研究振荡流动双折射（OFB）和粘弹性（VE）的聚合物溶液受到小振幅，周期性时变剪切流的条件下，将探索整个运动制度的重要性，在这些实验中进行。一些研究将利用定制仪器在高粘性溶剂中进行宽有效频率范围的测量，这也提供了重要的温度依赖性信息；其他仪器提供中高频率的数据将被用于在低粘度溶剂中获得广泛的频率覆盖。溶质诱导的溶剂动力学修饰、溶质浓度、温度、分子量、总链几何形状（分支）、溶剂质量以及不同聚合物和溶剂种类对OFB和VE性能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。将对不规则梳状（随机放置的分支位点）、随机分支链和具有空间变化流体动力相互作用的链进行聚合物对VE和OFB性能贡献的频率依赖性的广义珠簧模型计算，以评估链动力学的潜力，特别是这些技术，用于详细的聚合物分支表征。还将进行稀嵌段共聚物溶液的OFB和VE性质的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型相结合的研究，特别是在溶剂对大分子运动的影响方面。＊＊＊

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. ***