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

技术总结：本研究的目的是阐明和量化二嵌段共聚物的润湿如何控制聚合物液滴在不混溶聚合物共混物中的分散。 具体而言，将合成单分散聚二甲基硅氧烷-聚异戊二烯（PDMS-b-PIP）二嵌段共聚物，并将这些组分添加到PDMS和PIP的不混溶共混物中，以配制定义明确的PDMS/PMDS-b-PIP/PIP模型体系。使用这些系统的优点是，取决于在液滴界面处的共聚物的量的液滴的聚结，可以在PDMS或PIP基质中进行研究，这两者在室温下都是熔融的。这些组分的使用将有助于确定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用于预测不混溶液滴的流变学。 具体地说，理论推导的图表能否预测液滴不稳定和聚结或稳定和分散的区域？ 为了探索这个问题，良好控制的流变实验将进行模型系统，这些实验的结果将进行比较，在聚合物介质中的不混溶液滴的流变行为的理论预测。 预计本研究的结果将提高对控制聚合物液滴分散到聚合物熔体中的机制的理解。这些发现将对工程材料的生产产生积极影响，当液滴均匀分散在整个混合物中时，这些材料的性能将得到优化。 非技术总结：研究人员有巨大的机会从与嵌段共聚物相容的不混溶聚合物共混物中创造先进的轻质材料。含有化学上与共混组分相同的嵌段的共聚物分离到聚合物之间的界面，这应该产生一种聚合物在另一种聚合物中的精细分散体。 然而，在实践中很少实现精细分散，因为液滴倾向于聚结，削弱共混物的性能。 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。 他们将合成和配制学术和工业兴趣的不混溶聚合物和嵌段共聚物的系统，并在良好控制的实验中研究这些系统的分散特性。 这项研究的一个中心目标是确定理论上推导出的相图是否可以用来预测液滴聚结或分散的区域。 合作者的初步研究结果表明，相图确实有助于预测液滴的聚结和分散。 来自NSF的资金将用于巩固这些关系，这些关系非常重要，因为它们可以用于提供用户友好的路线图，以设计汽车零部件，医用织物和绝缘产品等先进材料。 此外，该研究的更广泛影响包括利用研究结果加强界面化学课程，并与当地学校联系，以增加UVa和VPI合格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.