Collaborative Research: Connecting the Wetting and Rheological Behaviors of Compatibilized Polymer Droplets in Immiscible Polymer Melts

技术摘要：本研究的目的是阐明和量化两嵌段共聚物的润湿如何控制聚合物液滴在不相容的聚合物混合物中的分散。具体地说，将合成单分散聚二甲基硅氧烷-聚异戊二烯(PDMS-b-PIP)两嵌段共聚物，并将这些组分添加到PDMS和PIP的不相容共混物中，形成定义良好的PDMS/PMDS-b-PIP/PIP模型体系。使用这些系统的优点是，可以在PDMS或PIP基质中研究液滴的聚结，这取决于液滴界面上的共聚物量，这两种基质都是室温熔融的。这些组分的使用将有助于建立取决于嵌段共聚物和基质聚合物的链长的润湿相图是否可以用于预测不相容液滴的流变性。具体地说，理论上得出的图表能否预测液滴不稳定和聚合的区域，或者液滴稳定和分散的区域？为了探索这个问题，将在模型系统上进行良好控制的流变性实验，并将这些实验的结果与聚合物介质中不相容液滴的流变性的理论预测进行比较。这项研究的结果有望加深对控制聚合物液滴在聚合物熔体中分散的机理的理解。这些发现应该会对工程材料的生产产生积极的影响，当液滴均匀分散在混合物中时，工程材料的性能会得到优化。非技术概述：研究人员有巨大的机会从不相容的聚合物混合物中创造出先进的、轻质的材料，使其与嵌段共聚物兼容。共聚物含有与共混组分在化学上相同的嵌段，隔离到聚合物之间的界面，这应该会使一种聚合物在另一种聚合物中形成良好的分散。然而，在实践中很少实现精细分散，因为液滴往往会聚集，从而削弱了共混物的性能。为了解决这个问题，弗吉尼亚大学(UVA)和弗吉尼亚理工学院(VPI)的研究人员将合作。他们将合成和配制具有学术和工业意义的不相容聚合物和嵌段共聚物体系，并在受控良好的实验中研究这些体系的分散特性。这项研究的一个主要目的是确定理论上得出的相图是否可以用来预测液滴聚集或分散的区域。合作者的初步发现表明，相图确实有助于预测液滴的合并和分散。来自NSF的资金将用于巩固这些关系，这些关系非常重要，因为它们可以用来提供用户友好的路线图，以设计先进材料，如汽车零部件、医用织物和绝缘产品。此外，研究的更广泛影响包括利用研究结果加强界面化学课程，并与当地学校接触，目的是增加UVA和VPI合格的工程和科学申请者的数量和多样性。

TECHNICAL SUMMARY:The objective of the research is to elucidate and quantify how the wetting of diblock copolymers governs the dispersion of polymer droplets in immiscible polymer blends. Specifically, monodisperse polydimethylsiloxane-polyisoprene (PDMS-b-PIP) diblock copolymers will be synthesized, and these components will be added to immiscible blends of PDMS and PIP to formulate of well-defined model systems of PDMS/PMDS-b-PIP/PIP. The advantage of using these systems is that the coalescence of the droplets, which depends on the amount of copolymer at the droplet interface, can be studied in either the PDMS or PIP matrices, which are both melts at room temperature. The use of these components will help to establish whether wetting phase diagrams, which depend on the chain lengths of the block copolymers and matrix polymers, can be used to predict the rheology of the immiscible droplets. Specifically, can theoretically derived diagrams predict the regions over which droplets are unstable and coalesce or are stable and disperse? To explore this question, well-controlled rheological experiments will be performed on the model systems, and the results of these experiments will be compared to theoretical predictions of the rheological behavior of immiscible droplets in polymeric media. It is expected that the results of this research will enhance the understanding into the mechanisms that control the dispersion of polymer droplets into polymer melts. These findings should positively impact the production of engineered materials whose properties are optimized when the droplets are evenly dispersed throughout the blend. NON-TECHNICAL SUMMARY:Tremendous opportunities exist for researchers to create advanced, lightweight materials from immiscible polymer blends made compatible with block copolymers. Copolymers, containing blocks chemically identical to the blended components, segregate to the interface between the polymers, which should produce a fine dispersion of one polymer in another. However, fine dispersions are rarely achieved in practice, because the droplets tend to coalesce, weakening the performance of the blends. To resolve this issue, researchers from the University of Virginia (UVa) and Virginia Polytechnic Institute (VPI) will collaborate. They will synthesize and formulate systems of immiscible polymers and block copolymers of academic and industrial interest, and investigate the dispersion characteristics of these systems in well-controlled experiments. A central thrust of the research is to determine whether theoretically derived phase diagrams can be used to predict the regions over which the droplets coalesce or disperse. Preliminary findings of the collaborators indicate that phase diagrams do aid in the prediction of droplet coalescence and dispersion. Funding from the NSF will be used to cement these relationships, which are important because they can be used to provide user-friendly roadmaps to engineer advanced materials such as automotive parts, medical fabrics, and insulation products. Moreover, broader impacts from the research include using the results to enhance a course on interfacial chemistry and reaching out to local schools with the goal of increasing the number and diversity of qualified engineering and science applicants to UVa and VPI.