Stacy L. Pesek

Amphiphilic poly(alkylthiophene) block copolymers prepared via externally initiated GRIM and click coupling

Block copolymers with a poly(3-alkylthiophene) (P3AT) polymer block can self-organize into periodic, crystalline nanostructures that may be useful for organic electronic applications. However, reliable synthetic methods for the preparation of P3AT block copolymers are lacking. Here, we demonstrate a general method for the synthesis of P3AT rod-coil block copolymers via click-coupling of alkynyl-P3AT. Alkynyl-P3ATs are prepared via externally initiated Grignard metathesis polymerization (GRIM) using a modified nickel catalyst followed by end-group modification. The resulting alkynyl-P3ATs have improved stability and solubility compared with those previously reported. P3ATs are subsequently coupled to an azide-functionalized poly(ethylene glycol) through copper-catalyzed azide–alkyne click coupling, resulting in P3AT-b-PEG block copolymers. The advantages of this synthetic procedure are the improved stability of the alkynyl-P3AT macroreagent, the capability to synthesize high molecular weight P3AT polymer blocks, and facile determination of P3AT absolute molecular weight through 1H NMR analysis. This synthetic method is applied to prepare a series of P3AT-b-PEG block copolymers, with poly(3-hexyl thiophene) (P3HT), poly(3-dodecylthiophene) (P3DDT), and poly(3-(2′-ethyl)hexylthiophene) (P3EHT) polymer blocks. The resulting P3AT block copolymers are dispersed in water to form micelles with crystalline, hydrophobic cores. Absorbance measurements show that crystallization of P3DDT and P3EHT blocks is suppressed in micellar cores due to nanoscale confinement of the P3AT blocks.

Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers.

Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion, eliminates cracking during cycling, and boosts cyclability relative to V2O5 alone. These results highlight the importance of tradeoffs between mechanical and electrochemical performance, where polymer content can be used to tune both aspects.