Advanced Tube Theories for Predicting the Rheolllogy of Model and Commercial Polymers

技术总结流变学对聚合物结构，包括分子量分布和长链支化分布，比任何其他可测量的性质更敏感。因此，对精心选择的聚合物熔体和溶液进行流变学测量具有很大的动力，这将提高将流变学与聚合物相对分子质量和支化分布联系起来的能力。提出了三个新项目。首先，我们将研究支链多分散性和主链长度对具有两个支点和四个支臂的定义良好的缠绕H聚合物的线性粘弹性的影响。最近的模型表明，H-支化聚合物应该具有对多分散性非常敏感的流变性，因此这些研究以及相应的理论工作将允许对这些理论进行强有力的测试，并有助于发展更准确的支化点运动理论。其次，使用陶氏化学公司的模型材料，将获得对分支点运动的高阶效应敏感的线性粘弹性数据，并用于测试现有算法-分层模型-准确预测这些数据的能力。第三个问题是测试聚合物溶液中线性和非线性流变性质的普遍标度原理，该原理认为，当以固定的c/Ce比率测量时，所有这些性质在以无量纲的形式绘制时，浓度与纠缠浓度叠加。这一概念将通过测量不同分子量的线性和非线性数据集，在几个固定的C/Ce值下进行彻底测试，并将这些测试扩展到线性聚合物的二元混合物。非技术概述超过2000亿磅的聚合物在全球范围内进行商业生产，并成型为各种产品。成型过程取决于它们的流动特性或流变性，而流变性又取决于分子特性，如分子量分布和支化分布。因此，更好地定义聚合物分子结构和流变学之间的关系是一个巨大的工业兴趣。这项拟议的工作将增加对这种关系的了解，导致在分子水平上设计出更好的聚合物。来自这笔赠款的见解，以及同一NSF项目过去的赠款，将有助于该计划者与陶氏化学公司和宝洁公司的合作。由提议人合著的新书《熔融聚合物的分子结构和流变学》今年出版，其中包含了美国国家科学基金会之前拨款的工作，根据新拨款开展的工作也将通过国际合作向美国工业界和海外广泛宣传。这些工作数据还将导致商业软件包IRIS的改进，该软件包用于预测在工业中广泛使用的聚合物熔体的流变性。

TECHNICAL SUMMARYRheology is more sensitive to polymer architecture, including molecular weight distribution and long-chain branching distribution, than is any other measurable property. Thus there is great motivation to carry out rheological measurements on well-chosen polymer melts and solutions that will lead to improved ability to link rheology to polymer molecular weight and branching distributions. Three new projects are proposed. First, the effects of polydispersity in arm and backbone length on the linear viscoelasticity of well defined entangled H polymers, which have two branch points and four arms, will be studied. Recent models show that H-branched polymers should have rheology that is very sensitive to polydispersity, so that these studies, along with corresponding theoretical work, will allow strong tests of these theories to be carried out, and help in the development of a more accurate theory of branch point motion. Second, using model materials from Dow Chemical Co., linear viscoelastic data will be obtained that will be sensitive to higher order effects of branch point motion and used to test the ability of an existing algorithm, the hierarchical model, to predict accurately these data. The third problem will be to test the principle of universal scaling of linear and nonlinear rheological properties in polymer solutions, which holds that all such properties, when measured at a fixed value of the ratio of c/ce, the concentration to the entanglement concentration superpose, when plotted in dimensionless form. This concept will be tested thoroughly by measuring sets of linear and nonlinear data for different molecular weights, at several fixed values of c/ce and by extending these tests to binary blends of linear polymers. NON-TECHNICAL SUMMARY Over 200 billion pounds of polymers are produced commercially worldwide, and shaped into a wide variety of products. The shaping processes depend on their flow properties, or rheology, which, in turn, depends on molecular characteristics, such as molecular weight distribution and branching distribution. Thus, there is a huge industrial interest in better defining the relationship between polymer molecular structure and rheology. The proposed work will increase knowledge of this relationship, leading to polymers that are designed better at the molecular level. Insights from this grant, and past grants from the same NSF program, will assist in collaborations the proposer has with Dow Chemical Co. and Procter and Gamble. A new book, co-authored by the proposer, Molecular Structure and Rheology of Molten Polymers, published this year, contains work from the previous NSF grants, and the work to be carried out under the new grant will similarly be well publicized, both to U.S. industry and overseas, through international collaborations. The work data will also lead to improvements in a commercial software package IRIS, for predicting rheological properties of polymer melts, that is used widely in industry.