Search for: All records

Affordable thin-film composite (TFC) membranes are a potential alternative to more expensive ion exchange membranes in saltwater electrolyzers used for hydrogen gas production. We used a solution-friction transport model to study how the induced potential gradient controls ion transport across the polyamide (PA) active layer and support layers of TFC membranes during electrolysis. The set of parameters was simplified by assigning the same size-related partition and friction coefficients for all salt ions through the membrane active layer. The model was fit to experimental ion transport data from saltwater electrolysis with 600 mM electrolytes at 10 mA cm–2. When the electrolyte concentration and current density were increased, the transport of major charge carriers was successfully predicted by the model. Ion transport calculated using the model only minimally changed when the negative active layer charge density was varied from 0 to 600 mM, indicating active layer charge was not largely responsible for controlling ion crossover during electrolysis. Based on model simulations, a sharp pH gradient was predicted to occur within the supporting layer of the membrane. These results can help guide membrane design and operation conditions in water electrolyzers using TFC membranes. 

π-Conjugated polymers that extend the π-conjugation in more than one dimension are highly sought after for various organic electronic and energy applications. However, the synthesis of solution processable higher dimensional π-conjugated materials is still at its infancy because of strong interchain π–π interactions. The conventional strategy of using linear alkyl pendant chains does not help overcome the strong interchain π–π interactions in higher dimensional π-conjugated materials as they do not directly mask the π-face of the repeat units. While the miniemulsion technique has been employed to generate hyperbranched π-conjugated polymer particles stabilized by surfactants, this approach does not address the molecular level challenges. We have proposed that π-face masking straps mask the π-face of the polymer backbone and therefore help to control π–π interchain interactions in higher dimensional π-conjugated materials at the molecular level. Herein, we have shown that when a strapped aryl dialdehyde monomer (A2) is reacted with a trifunctional 1,3,5-benzenetriamine (B3) using dynamic imine chemistry, a solution dispersible and processable hyperbranched polymer with a degree of branching of 0.46 is generated. Also, by varying the reaction conditions (catalyst, monomer concentration, and solvent), solution dispersible polymer particles of varying diameters ranging from 60 to 300 nm are generated. It is worth noting that despite having the suitable monomer architectures for the formation of ordered frameworks, a hyperbranched polymer is generated because the straps effectively hinder interlayer π–π stacking interactions, thereby preventing the formation of crystalline aggregates that are required for the growth of the former. Since straps stabilize the chains against π–π interactions at the molecular level, they will not only provide synthetic control over the architecture but also remove typical synthetic limitations associated with the miniemulsion technique including functional group intolerance and monomer miscibility. 

Controlling network growth and architecture of 3D-conjugated porous polymers (CPPs) is challenging and therefore has limited the ability to systematically tune the network architecture and study its impact on doping efficiency and conductivity. We have proposed that π-face masking straps mask the π-face of the polymer backbone and therefore help to control π–π interchain interactions in higher dimensional π-conjugated materials unlike the conventional linear alkyl pendant solubilizing chains that are incapable of masking the π-face. Herein, we used cycloaraliphane-based π-face masking strapped monomers and show that the strapped repeat units, unlike the conventional monomers, help to overcome the strong interchain π–π interactions, extend network residence time, tune network growth, and increase chemical doping and conductivity in 3D-conjugated porous polymers. The straps doubled the network crosslinking density, which resulted in 18 times higher chemical doping efficiency compared to the control non-strapped-CPP. The straps also provided synthetic tunability and generated CPPs of varying network size, crosslinking density, dispersibility limit, and chemical doping efficiency by changing the knot to strut ratio. For the first time, we have shown that the processability issue of CPPs can be overcome by blending them with insulating commodity polymers. The blending of CPPs with poly(methylmethacrylate) (PMMA) has enabled them to be processed into thin films for conductivity measurements. The conductivity of strapped-CPPs is three orders of magnitude higher than that of the poly(phenyleneethynylene) porous network.