Versatile polyelectrolytes with tunable physical properties have the potential to be transformative in applications such as energy storage, fuel cells and various electronic devices. Among the types of materials available for these applications, nanostructured cationic block copolyelectrolytes offer mechanical integrity and well-defined conducting paths for ionic transport. To date, most cationic polyelectrolytes bear charge formally localized on heteroatoms and lack broad modularity to tune their physical properties. To overcome these challenges, we describe herein the development of a new class of functional polyelectrolytes based on the aromatic cyclopropenium ion. We demonstrate the facile synthesis of a series of polymers and nanoparticles based on monomeric cyclopropenium building blocks incorporating various functional groups that affect physical properties. The materials exhibit high ionic conductivity and thermal stability due to the nature of the cationic moieties, thus rendering this class of new materials as an attractive alternative to develop ion-conducting membranes.

The potential applications of cationic poly(ionic liquids) range from medicine to energy storage, and the development of efficient synthetic strategies to target innovative cationic building blocks is an important goal. A post-polymerization click reaction is reported that provides facile access to trisaminocyclopropenium (TAC) ion-functionalized macromolecules of various architectures, which are the first class of polyelectrolytes that bear a formal charge on carbon. Quantitative conversions of polymers comprising pendant or main-chain secondary amines were observed for an array of TAC derivatives in three hours using near equimolar quantities of cyclopropenium chlorides. The resulting TAC polymers are biocompatible and efficient transfection agents. This robust, efficient, and orthogonal click reaction of an ionic liquid, which we term ClickabIL, allows straightforward screening of polymeric TAC derivatives. This platform provides a modular route to synthesize and study various properties of novel TAC-based polymers.

The self-assembly of diblock copolymers (BCPs) comprising flexible polymer chains, driven by a balance of enthalpic and entropic forces, is well understood. If one of the blocks is a polyelectrolyte, forming a chargeneutral BCP (CN-BCP), Coulombic interactions can play a significant role in the self-assembly. Here, electron microscopy and small-angle X-ray scattering, in combination with free-energy arguments and a scaling model inspired by surfactant self-assembly, are used to investigate the microphase segregation of CN-BCPs having pendent trisaminocyclopropenium (TAC) ions. We find that the TAC polymer electrolytes have an unexpectedly low dielectric constant (∼2.5) and that CN-BCPs containing a TAC polymer electrolyte block exhibit highly asymmetric morphology diagrams. These CN-BCP morphology diagrams have an unexpectedly large range of CN-BCP compositions where cylinders form, with the TAC block forming the continuous matrix, and in contrast to conventional BCPs, these cylindrical phases form even when the charged block is a minority constituent. These unusual morphologies observed in CN-BCPs with strong electrostatic interactions may thus provide a foundation for the exploration of new modes of ion transport in BCP selfassemblies.

A novel nanoparticle-based imaging strategy is introduced that couples biocompatible organic nanoparticles and stimulated Raman scattering (SRS) microscopy. Polymer nanoparticles with vibrational labels incorporated were readily prepared for multicolor SRS imaging with excellent photo-stability. The Raman-active polymer dots are nontoxic, rapidly enter various cell types, and are applied in multiplexed cell-type sorting.

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