The overarching goal of this advanced materials research is to understand how the ability to transform surface-attached polymeric layers so-called polymer brushes by chemical reaction is impacted by properties such as surface density, extent of the chains tethered at the interface, size of the functionalizing agent present in free solution, and reaction time and conditions. While reactive polymer brushes are of widespread interest, design rules that guide selection of appropriate conditions for integrating functional groups remain undeveloped and largely unexplored. To address this gap in knowledge, reactive polymer brushes will be created and modified in situ, and the ability of the chemically-modified interfacial layers to nucleate the growth of mineral phases will also be investigated. All of these studies will enhance the design of functional polymeric interfacial coatings, leading to new long term opportunities for the design of biomaterial scaffolds for cell growth, active layers in sensors, microarrays or membranes, and lubricious, wear-resistant, or anti-fouling coatings.
Intellectual Merit: Understanding the location and distribution of functional groups installed in interfacial layers is a complex and challenging proposition because the nanoscale structure and its ability to be chemically transformed are intimately coupled: changes in the distribution of chemicaln tags in the layer and the degree-of-functionalization impact the structure and properties of the interfacial layer. To address this challenge, reactive polymer brushes based on poly(tert-butyl methacrylate) and poly(vinyl dimethylazlactone) will be studied. Both uncatalyzed and catalyzed reactions using sets of molecules ranging in size from oligomeric to polymeric will be investigated. The nanoscale structure of the modified brushes will be determined using neutron reflectivity, and a creative application of isotopic labeling in concert with contrast matching strategies will be used to determine the local density of functional groups installed in the brushes. To investigate how the display of chemical motifs affects the capacity of a layer to function, the nucleation and growth of calcite phases in modified polymer layers will be examined, providing a much-needed view of how calcium mineral phases form in synthetic polymer matrices. These activities will benefit from a new international collaboration that brings expertise in calcium mineralization in polymer matrices.
Broader Impacts: Design rules that express how the nanoscale structure of polymer brushes is coupled to the arrangement, size and density of functional groups displayed in the layer will promote the efficient and optimal design of useful devices and constructs based interfacial polymer layers. For example, understanding the links between the display of functional motifs in polymer scaffolds and the growth of calcium mineral phases may advance the development of biomimetic constructs that help close the gap between synthetic and natural composite materials such as bone. The fundamental research can be classified as advanced interfacial materials research at and for interfaces, bio-medical advanced materials, and materials for possible long term sensor applications.
In addition to promoting the training of graduate and undergraduate students and a postdoctoral scholar through engagement in research, collaborations with scientists at national laboratories and from EcolÃ© Polytechinque FÃ©dÃ©rale de Lausanne (Switzerland) will enhance the professional growth and development of researchers involved, aided in part by planned exchange visits. Research activities undertaken in this program will be supplemented with outreach and mentoring activities that will bolster the recruitment, retention, and success of students from under-represented groups. Finally, results from the research activities will be communicated through publications and presentations by all participants involved in the program, and a symposium on reactive polymer interfaces will be organized for an upcoming national meeting.