Particles at polymer/polymer interfaces: Interfacial phenomena and morphology control in immiscible polymer blends

聚合物/聚合物界面处的颗粒：不混溶聚合物共混物中的界面现象和形态控制

• 批准号: 0932901
• 负责人: Sachin Velankar
• 金额: $ 29.01万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0932901&HistoricalAwards=false
• 关键词: Particles; polymer; interfaces; Interfacial; phenomena

09329091 Velankar Particles that are partially wetted by oil and water are well known to adsorb at oil/water interfaces. Such interfacially adsorbed particles can stabilize emulsions of oil and water, and these emulsions are called Pickering emulsions. We seek to transplant this idea of Pickering emulsions to polymeric systems: specifically to create stable morphologies composed of two immiscible homopolymer phases and interfacially adsorbed particles. Previously we have shown that particles readily adsorb at the interface between a variety of polymers, and that even a small fraction (well under 1 vol. %) of particles can greatly affect the morphology of droplet/matrix polymer blends. Furthermore, when particles are sufficiently crowded at the interface, they jam the interface into a solid like state that prevents interfacial tension driven changes of the morphology. Here we propose a comprehensive experimental study of the effects of interfacially active particles in immiscible polymer blends. We hypothesize that particles that adsorb at the interface between two immiscible homopolymers can be used to control the morphology of the blend, in particular they can control the sizescale of the morphology, create highly anisotropic (cylindrical or lamellar) morphologies, as well as generate a new type of layered structure.Research Proposal: Experiments will be conducted on a model pair of homopolymers,(crosslinkable polyisoprene (PI) and polydimethylsiloxane (PDMS)), and silica particles that are surfacemodified to adsorb at the PI/PDMS interface. In situ flow visualization experiments will be conducted under shear flow conditions to characterize the morphology. Particle scale imaging will be performed ex situ by crosslinking the PI, washing away the uncrosslinked PDMS, and then conducting SEM of the particle laden interface. In initial research, we will devise flow protocols that induce the particles to rapidly adsorb at the interface, and induce them to crowd at the interface to cause interfacial jamming. We will also examine whether particles aggregate or spread on the interface, and whether they reduce the interfacial tension. The core of the research then is to test the above hypothesis about morphology control. The effect of particles on the flow induced morphology will be examined as a function of the relative volumes of the PI and PDMS, the particle loading, and the wettability of the particles. The ability of the particles to control the sizescale of the morphology and their ability to stabilize anisotropic morphologies by interfacial jamming will be examined. Finally, at high particle loadings when the particles tend to form layers in shear flow, we will examine whether these particle layers can template a PI/PDMS alternating lamellar morphology.Intellectual merit: This proposal unites knowledge in three different areas: interfacially adsorbed particles in oil/water systems, polymer compatibilizers at polymer/polymer interfaces, and the flow induced morphology in polymer blends. These ideas are combined together to develop particulate compatibilizers particles that act as interfacial modifiers in polymeric systems in a fashion similar to block copolymer compatibilizers. Such particulate compatibilizers have the potential for achieving morphology control far beyond what is possible with conventional block copolymer compatibilizers. During the course of this research, we will also address several practical and fundamental issues such as how to rapidly adsorb the particles on the interface, and whether particles reduce the interfacial tension of polymeric interfaces. Finally, the PI has had success with transplanting several concepts from oil/water systems to polymeric systems, and this proposal goes considerably further in that direction.Broader impact: This proposal will develop a new mechanism to precisely control the morphology of polymer blends, and develop a new type of particle templated morphology composed of alternating layers of two immiscible polymers with particles at each interface. One graduate student and several undergraduates will be trained. The PI will develop a new hour long undergraduate level module on wetting phenomena for engineers combining hands on experiments with theoretical discussion. This is a part of a series of modules on soft matter that will be made available publicly.

众所周知，被油和水部分润湿的Velankar颗粒吸附在油/水界面处。这种界面吸附的颗粒可以稳定油和水的乳液，并且这些乳液被称为皮克林乳液。我们试图将皮克林乳液的这一想法移植到聚合物体系中：特别是创造由两个不混溶的均聚物相和界面吸附颗粒组成的稳定形态。以前，我们已经表明，颗粒很容易吸附在各种聚合物之间的界面处，即使是一小部分（低于1体积%）的颗粒可以极大地影响液滴/基体聚合物共混物的形态。此外，当颗粒在界面处足够拥挤时，它们将界面堵塞成类似固体的状态，这防止了界面张力驱动的形态变化。在这里，我们提出了一个全面的实验研究界面活性粒子在不混溶聚合物共混物的影响。我们假设吸附在两种不混溶均聚物之间的界面处的颗粒可以用于控制共混物的形态，特别是它们可以控制形态的尺寸尺度，产生高度各向异性，（圆柱形或层状）形态，以及产生一种新型的层状结构。研究建议：实验将在均聚物（可交联聚异戊二烯（PI）和聚二甲基硅氧烷（PDMS））和表面改性以吸附在PI/PDMS界面的二氧化硅颗粒的模型对上进行。将在剪切流条件下进行原位流动可视化实验以表征形态。通过交联PI，洗去未交联的PDMS，然后对载有颗粒的界面进行SEM，将非原位进行颗粒尺度成像。在初步研究中，我们将设计流动协议，诱导颗粒快速吸附在界面上，并诱导它们在界面上拥挤，造成界面堵塞。 我们还将研究颗粒是否在界面上聚集或扩散，以及它们是否降低界面张力。本研究的核心是检验上述关于形态控制的假设。 将检查作为PI和PDMS的相对体积的函数，颗粒负载，和润湿性的颗粒上的流动诱导形态的颗粒的效果。将检查颗粒控制形态的尺寸尺度的能力以及它们通过界面堵塞来稳定各向异性形态的能力。最后，在高颗粒负荷时，颗粒往往会形成层的剪切流，我们将研究这些颗粒层是否可以模板PI/PDMS交替层状morphology.Intellectual优点：这个建议统一在三个不同领域的知识：在油/水系统中的界面吸附颗粒，聚合物/聚合物界面的聚合物相容剂，和聚合物共混物中的流动诱导形态。这些想法结合在一起，以开发颗粒状增容剂颗粒，其以类似于嵌段共聚物增容剂的方式在聚合物体系中充当界面改性剂。这种颗粒增容剂具有实现形态控制的潜力，远远超过常规嵌段共聚物增容剂的可能性。 在本研究过程中，我们还将解决几个实际和基本的问题，如如何快速吸附在界面上的颗粒，以及颗粒是否降低聚合物界面的界面张力。最后，PI已经成功地将几个概念从油/水体系移植到聚合物体系中，并且该提案在该方向上走得更远。更广泛的影响：该提案将开发一种新的机制来精确控制聚合物共混物的形态，并开发一种新型的颗粒模板形态，该形态由两种不混溶的聚合物的交替层组成，每个界面处都有颗粒。将培养一名研究生和几名本科生。PI将为工程师开发一个新的长达一小时的润湿现象本科水平模块，将实验与理论讨论相结合。这是将公开提供的关于软物质的一系列模块的一部分。