Herein, a simple synthetic method to functionalize norbornene at the 5-position with a base-stable tetraaminophosphonium cation was developed. Upon confirmation that the cationic monomer could be polymerized in a living fashion, statistical and diblock copolymers were synthesized with norbornene as a comonomer. After hydrogenation, the statistical copolymers were effective anion-exchange materials, while the diblock did not produce a free-standing film. Differential scanning calorimetry and atomic force microscopy indicated that crystallinity was mostly suppressed by the bulky phosphonium cations in the statistical copolymers, with the impact somewhat dependent on the amino groups bound to the phosphorus atom. Small-angle X-ray scattering profiles revealed a two-phase morphology with 3 nm domains arising from ion clustering in the film. Altogether, the study revealed the large impact these novel phosphonium cations have on polymer organization and packing, which is a critical consideration when targeting larger delocalized cations in anion-transport materials.

Block copolymers have shown promise in ion-exchange membranes as they can phase separate into well-defined nanostructures which promote transport. Herein, a systematic study of multiblock copolymers containing cationic blocks is presented (diblock up to pentablock), and these were contrasted against a statistical copolymer. A series of vinyl addition polynorbornene anion-exchange membranes were prepared by copolymerization of 5-n-hexyl-2-norbornene and 5-(4-bromobutyl)-2-norbornene, followed by conversion of the halide to a trimethylammonium group. The hydroxide conductivities of all synthesized block copolymers were higher than the statistical copolymer, with the tetra and pentablock copolymers being the most conductive. The higher conductivity of the multiblocks is likely a combination of the increased surface-to-volume ratio (smaller domain sizes) improving the connectedness of ionic domains. Water uptake of the block copolymers was also dependent on the number and order of blocks. Copolymers with ionic blocks at one chain end took up more water than those where the ionic segments were confined to the chain interior. Finally, a method was developed to attach alkaline-stable tetraaminophosphonium cations to the bromo-functionalized statistical and pentablock polynorbornene. Interestingly, the synthesized phosphonium polymers had double the water uptake of their ammonium counterparts, which was attributed to the larger occupied volume of the phosphonium as compared to the ammonium group.

Hydroxide-exchange membrane (HEM) electrolyzers can produce green H2 with only earth-abundant catalysts and electrolyte-free (nominally pure) water feed, significantly decreasing system cost and complexity. However, HEM technology suffers from short...

In this study, we aimed to decrease segmental mobility in ring-opened polynorbornene anion-exchange membranes (AEMs) as a strategy to suppress swelling. This was accomplished by copolymerization of a norbornene-anthracene cycloadduct with cationic tetraaminophosphonium norbornene monomers to afford AEMs with glass transition temperatures above 100 °C. The anthracenyl side groups appended to the poly(vinylene-1,3-cyclopentylene) chain resulted in lower water uptake for the phosphonium-functionalized AEM when compared to an analogue without the arene moiety. Though chemical aging of these AEMs was noted over time, the benefits of rigidifying the polymer backbone were clear. Additionally, we have noted that the choice of dialkylamino groups around the phosphorus center plays a key role in alkaline stability of these phosphonium-based AEMs.

This study introduces a novel class of imidazolium- and ammonium-based ionic liquids possessing two C12 and C14 tails and thioether linkers designed for lipoplex-mediated DNA delivery. Imidazolium-based ionic liquids displayed efficient gene delivery properties with low toxicity. Thiol-yne click chemistry was employed for the facile and robust synthesis of these thioether-based cationic lipioids with enhanced lipophilicity and low fluidity.