Synthesis of Polypropylene via Catalytic Deoxygenation of Poly(methyl acrylate).

We propose the defunctionalization of vinyl polymers as a strategy to access previously inaccessible polyolefin materials. By utilizing B(C6F5)3-catalyzed deoxygenation in the presence of silane, we demonstrate that eliminating the pendent ester in poly(methyl acrylate) effectively leaves a linear hydrocarbon polymer with methyl pendants, which is polypropylene. We further show that a polypropylene-b-polystyrene diblock copolymer and a polystyrene-b-polypropylene-b-polystyrene triblock copolymer can be successfully derived from the poly(methyl acrylate)-containing block polymer precursors and exhibit quite distinct materials properties due to their chemical transformation. This unique postpolymerization modification methodology, which goes beyond the typical functional group conversion, can offer access to a diverse range of unprecedented polyolefin block polymers with a variable degree of functional groups.

Control of Ion Transport in Sulfonated Mesoporous Polymer Membranes.

We investigated proton conductivity and the permeability of monovalent cations across sulfonated mesoporous membranes (SMMs) prepared with well-defined pore sizes and adjustable sulfonic acid content. Mesoporous membranes with three-dimensionally continuous pore structure were produced by the polymerization-induced microphase separation (PIMS) process involving the reversible addition-fragmentation chain transfer (RAFT) copolymerization of styrene and divinylbenzene in the presence of a polylactide (PLA) macrochain transfer agent and subsequent PLA etching. This allowed us to control pore size by varying PLA molar mass. Postsulfonation of the mesoporous membranes yielded SMMs whose pore structure was retained. The sulfonic acid content was adjusted by reaction time. While proton conductivity increased with increasing ion exchange capacity (IEC) without noticeable dependence on the pore size, ion permeability was strongly influenced by the pore size and IEC values. Decreasing pore size and increasing IEC resulted in a decrease in ion permeability, suggesting that ions traverse across the membrane via the vehicular mechanism, through the mesoporous spaces filled with water. We further observed that the permeability of the vanadium oxide ion was dramatically suppressed by reducing the pore size below 4 nm, which was consistent with preliminary vanadium redox flow battery data. Our approach suggests a route to developing permselective membranes by decoupling proton conductivity and ion permeability, which could be useful for designing separator materials for next-generation battery systems.