Charged block copolymer solution assembly will be used to construct extraordinary polymer nanostructures. The understanding of the mechanisms by which such assemblies form, and the harnessing of those processes to achieve well-defined, reproducible nanostructured materials, will be sought. The syntheses of, and experiments with, block copolymers based on both currently studied and new block chemistries will help produce this understanding. A fundamental understanding will be sought of the effects that multivalent, organic counterions complexing with charged corona chains of block copolymers have on the charged block conformation as well as the overall morphology formed during polymer self-assembly. The work will explore a series of multiamines towards this purpose. Likewise a series of triblock vs. diblock copolymers will be made to explore the effects of chain architecture and relative composition between blocks, as well as new hydrophobic core chemistry. The new core chemistry allows for blending experiments in order to kinetically trap multiple molecule types in the same assembled nanostructure. The new chemistries will also allow experiments to a) be performed in pure water as opposed to THF/H2O mixtures thus greatly simplifying assembly protocols as well as b) permit the photodegradation of hydrophobic cores for the production of potentially functional, porous polymer nanoparticles. In summary, a simple but transformative solution assembly paradigm for creation of complex polymer nanostructures for potential technology will be sought.
NON-TECHNICAL SUMMARY:
The proposed materials science will work towards two important needs. First, the technical results will help work towards making nanotechnology a reality for future technology ranging from energy to biomedical applications. More complex nanostructures are needed for future technology, and this work strives to create new methods to produce the needed nanostructure. Second, by performing the research, graduate students will be trained in scientifically rigorous, interdisciplinary environments, critical components for their future successes in the U.S. work force. At the undergraduate and graduate levels, collaborative scientific foundations will be developed during the proposed research by integrating educational expertise in the multi- and interdisciplinary fields of synthetic polymer chemistry, physical chemistry, polymer physics and materials science and engineering. Exchange of knowledge and expertise will be accomplished by a dynamic exchange of personnel between the University of Delaware and Texas A&M University. In each of the four years of support, each of the students will engage in collaborative research by conducting site exchanges for multiple and extended periods of time. Perhaps one of the greatest possible outcomes of the proposed work is the translation of knowledge uniformly to the chemists and materials scientists/engineers involved in the research.
The broader impacts of this proposal are of far reaching importance in terms of scientific advances, educational outreach, and student development through active mentorship. This collaborative research proposal constitutes a unique base for research and educational activities, each at the forefront of the fields of polymer chemistry, physical chemistry, polymer physics and materials science. The graduate students supported by this collaborative grant will be trained additionally through involvement with the development and implementation of established outreach activities in the Wooley group including K-12 educational outreach activities (assisting with the teaching of a semester-length course on hands-on experiments for K-8 teachers, educational visits to and by local pre-college students in Newark through the Materials Awareness Program or MAP), and it is expected that each student will spend up to a week per year involved in K-12 activities.
It is critical for today’s technology, as well as technology in the future, for scientists and engineers to be able to build desired materials on the nanoscale (~structures spanning distances that are 1/100th-1/10000th of the thickness of a human hair). Scientists and engineers are quite good at producing material structures on small, nanoscale length scales. Photolithographic techniques (also called "top-down" techniques since they use machines to draw/etch/dig out patterns in layers of materials) are used in the electronics industry to produce nanoscale structures in semiconductors and metallic materials that make computers, smart phones and gaming systems work quickly and display visually. However, these materials are produced only through complex, expensive, hierarchical, industrial techniques. In addition, these structures, important for electonics, are limited to lines, edges and holes in the materials commonly used in electronics (e.g. polymeric photoresists, metallic conductors, ceramic semiconductors). There are other laboratory-scale techniques such as electron lithography that can produce nanometer scale patterns in materials, but these methods are slow, expensive, and not useful to the production or manufacture of materials for technology. In essence, the broader impacts of the project were to explore and develop new methods for the production of nanostructures in materials (in this case, polymer materials) that can be produced in easy ways, such as simple mixing in solution, with no lithography or other expensive method required. This type of solution mixing methods are known as "bottom-up" methods because all of the information needed to produce a desired nanostructure is encoded into the molecules of the polymers and solvent in which they are dissolved. This method is also known as "self-assembly" to emphasize the fact that the polymers have the information needed to force them to find each other in solution and to zip together to build a desired nanostructure. If one could perform bottom-up self-assembly of technology, one would revolutionize the technology that could be produced by such cheap, easy methods. Another important facet of the broader impacts is the extensive, interdisciplinary training obtained by the people involved in the research. As mentioned earlier, both chemistry and physics are an important part of the research. Therefore, students involved needed to be an expert in one area but also well trained in the other in order to work together and get results. The leaders of the project (Darrin Pochan in Materials Science and Engineering at the University of Delaware and Karen Wooley in Chemistry at Texas A&M University) worked hard with an array of graduate and undergraduate students to provide extensive education, training and recruitment of the next generation of interdisciplinary chemists and materials scientists. The students gained expertise in synthetic organic/polymer chemistry and materials physics/materials science and engineering, (2) advanced synthetic polymer chemistry, (3) advanced materials solution construction methods (i.e. self-assembly), and (4) created novel materials that have the potential to positively impact society. The Chemistry students in Texas were trained in synthetic organic and polymer chemistries of challenging block copolymer systems; gained expertise in supramolecular chemistry to create intricate nanostructured materials; and were exposed to engineering and nanoscale characterization concepts. Engineering students were trained in materials physics of solution assembly, nanoscale characterization, and were exposed to polymer chemistry and molecular characterization concepts. This interdisciplinary training is critical for the future tech workforce in the U.S. in order to compete globally and to create the technology needed to tackle challenges in the future. The intellectual merit of the project can be seen in the new nanostructures that were constructed and that have never been observed before or predicted. An important result of the work is a general method to produce complicated nanostructures with desired compartments and shapes through simply solution self-assembly methods with polymers. Specifically, the polymers were block copolymers where one has different polymer molecules with different chemistry and different properties connected together into one chain to form a block copolymer. By trapping block copolymers into nanostructures, the different blocks separate into their own compartments with a unique shape and material property. The project that has now ended has provided the research team with a foundation that is being built upon to produce new materials with even more complexity and, eventually, function for nanomaterials needed in optics, electronics and biomedicine. This work would not have been possible without the support of the National Science Foundation. It is critical for the U.S. to continue support (more importantly, to grow support) for fundamental research made possible by the NSF. Fundamental research is from where transformative technologies (and the companies and employees that eventually produce the technology) are created and problems solved. Without the NSF, the U.S. loses a critical component to our nation’s future in technology and business.
