Nanoparticles as Surfactants: Static and Dynamic Properties

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0932259Leal"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."The interfacial activity of copolymers and polymer functionalized nanoparticles in multiphase polymer systems holds deep scientific interest and enormous industrial importance. In addition to the variety of basic science questions they raise, these synthetic compatibilizers enable blends of immiscible polymers. Moreover, the core material of functionalized nanoparticles may offer additional chemical or physical functionality (magnetic, optical, thermal or electronic). However, even a basic understanding of how they work remains lacking. The research aims to measure, predict, and model the static and dynamic properties of nano-particle and co-polymer surfactants. Without such capability to make such measurements, and thus to develop a fundamental understanding of their operation, the rational design of synthetic compatibilizers for advanced polymer blends will remain impossible.Intellectual merit. The central intellectual merit of the proposed project is to develop and apply new techniques to measure and understand the static and dynamic properties of synthetic co-polymer and nanoparticle "surfactants" at polymer/polymer interfaces, essentially for the first time. This requires three specific aims be achieved:(1) To develop novel micro-scale techniques and tools. Two new and novel techniques will be developed: a micro-tensiometer, and an active microrheology technique to measure the surface viscoelasticity and nonlinear viscosity of the compatibilizer laden interface; (2) To use these new tools to measure and characterize the statics and dynamics of nanoparticle and copolymer surfactants. Specifically, surface pressure vs. concentration isotherms, surfactant diffusivity and interfacial viscoelasticity will be measured for nanoparticle and copolymer surfactants, whose properties are varied in a systematic and comprehensive manner; and (3) To develop theories that capture the measured behavior and make testable predictions; so as to generalize our results, provide an intuitive understanding of the mechanisms by which these synthetic compatibilizers work, and guide design rules. The proposed work is potentially highly transformative: not only does it propose to develop novel and unprecedented measurement capabilities, but also to develop fundamental and general understanding of the static and dynamic behavior of copolyer and nanoparticle surfactants, as well as intuition for how to design them.Broader impact. The broader impact of the proposed work is quite substantial. First, the measurement tools to be developed require only minute quantities of sample, yet would enable a control over interfacial composition and the measurement of interfacial tension and rheology, that would be unprecedented. This aspect of the proposed work would be truly transformative in terms of the information it would make accessible. The specific measurements would be the first of their kind, and would allow the first steps toward a fundamental understanding of the static and dynamic properties of nano particle surfactants at polymer/polymer interfaces. Such understanding would be potentially transformative as well, in that it that would enable the rational design and processing of advanced polymeric materials with desired properties. The groups will continue to be active in recruiting and mentoring under represented minority students and generally ambitious undergraduates in summer and academic year research projects, by leveraging the nationally recognized outreach infrastructure in UCSB's Materials Research Laboratory. A high school teacher will be involved in summer research, to impact his/her own experience as well as his/her students in future years. To reach out to the broader university community, a freshman seminar course will be developed for non-science students on the science and engineering of rheologically interesting products familiar from everyday life including foods and personal care products. The idea is to expose students to the interesting, ubiquitous and surprisingly understandable world of materials that are neither solid nor liquid. As part of this course, the investigators will post lecture notes and demonstration videos freely on the internet; following its successful development, we will write a descriptive article for Chemical Engineering Education, to encourage and facilitate related course content for other undergraduate or high school programs.