Chain Growth Polycondensation via Substituent Effects for the Synthesis of Functional Rigid Rod Polymer Brushes

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The modification of surfaces with polymers is widely used in the development of new technologies or the improvement of existing technologies, ranging from sensors to smart coatings. Coating by physically adsorbing polymers on surfaces is a more versatile approach, but it suffers from the issue of leaching. Chemically attaching polymers on surfaces provides more robust and longer lasting coatings, but current synthetic techniques limit the molecular structures and architectures of polymers that can be attached. To tackle this problem, Professors Boyes and Vyas of the Colorado School of Mines are developing a new surface-initiated polymerization technique for "growing" polymers of desired architectures and properties directly from a variety of different surfaces. A potential application of this synthetic methodology is the preparation of novel membranes for the removal of salt from seawater. Access to clean drinking water is a critical problem facing many people across the globe and the removal of salt from seawater or brackish water has become an important technique for providing drinking water to regions that suffer from limited sources of fresh water. This project also provides research opportunities to graduate and undergraduate students. In addition, outreach programs to local high schools are established to educate and stimulate the next generation of scientists and engineers.In this project, the research team focuses on developing a new surface-initiated polymerization technique based on the chain growth polycondensation via substituent effects mechanism (SECGP) for preparing aromatic polymer brushes with well-defined structures and properties. The specific objectives of the project are: 1) to design and synthesize N-substituted aminobenzoate monomers with a variety of ester leaving groups, amino groups, and substituents on the aromatic ring; 2) to investigate the effects of monomer structures and polymerization conditions on reaction kinetics and properties (such as molecular weight and solubility) of the resulting aromatic polyamides; 3) to perform density functional theory (DFT) calculations to elucidate the steric and electronic effects of the monomer structures on the polymerization mechanism and kinetics; 4) to conduct surface initiated SECGP on silica substrates, investigate the effect of surface properties on the formation of aromatic polymer brushes (including block copolymer brushes), and probe the structure-property relationships of these new polymer brushes; and 5) to prepare aromatic polyamide brushes on ceramic membranes and test their performance in water desalination. A potential application is in reverse osmosis membranes, where these new brushes can overcome issues with coating instability, biofouling, and reduced flux capacity that limit current polymer membranes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.