I. Depolymerization-macrocyclization of (o-phenylene-ethynylene)-alt-(arylene-ethynylene) copolymers. II. Improving existing water filtration membranes via covalent modification

I. Depolymerization-Macrocyclization of (o-Phenylene-Ethynylene)- alt-(Arylene-Ethynylene) Copolymers: The synthesis of shape-persistent arylene-ethynylene macrocycles via alkyne metathesis remains an open area of investigation due to gaps in understanding about how monomer structure affects product distribution. In our efforts to close this gap, we studied how monomers with two different geometries would mix under metathesis conditions to form distributions of macrocycles using a depolymerization-macrocyclization method. Instead, we found that starting with (o-phenylene-ethynylene)- alt-(arylene-ethynylene) copolymers resulted in selective formation of the alternating macrocycles even with a diverse set of co-monomers. Through testing various theories, we propose that this selectivity is due to a regioselective interaction of the molybdenum catalyst with the asymmetric alkyne so that the reaction cannot reach the thermodynamic product distribution.;II. Improving Existing Water Filtration Membranes via Covalent Modification: Over a billion people in the world already have limited access to safe drinking water, and the problem is steadily growing worse due to contamination of our water supply. Therefore, we need an efficient, sustainable method for the purification of water that can remove the wide array of toxic solutes in water. Reverse osmosis is an attractive technique for water purification because of how versatile it is, with a range of membrane materials that can potentially be optimized to exhibit certain properties, such as selective rejection of certain solutes and permeation of others. Our collaboration has previously demonstrated the use of polyaramide dendrimers to improve commercial filtration membranes, though the coating was found to be unstable and the beneficial effects were lost over time. Thus, we have now developed a method for covalently attaching the dendrimer to the active layer of the membrane. The covalently modified membranes have improved filtration properties relative to the original membrane and have been shown to be more stable than the analogous dendrimer coating.