Cascade Cyclopolymerization of 5‐Ethynyl‐1,8‐Nonadiyne Derivatives to Synthesize Low Band Gap Conjugated Polyacetylenes Containing a Fused Bicyclic Structure

Abstract

Cyclopolymerization is a powerful method for synthesizing polyacetylenes containing four-to sevenmembered rings. However, the structure of the repeat unit only consists of mono-cycloalkene due to the single cyclization of diyne monomers. Herein, we demonstrate a novel cascade cyclopolymerization to synthesize polyacetylenes containing fused bicyclic rings from triyne monomers containing bulky dendrons via sequential cascade ring-closing metathesis. These dendrons provided solubility and stability to the rigid bicyclic polyacetylene backbone. In addition, we controlled the regioselectivity of the catalyst approach by altering its structure and synthesized polymers containing fused bicyclo [4,3,0] or [4,4,0] rings with high molecular weights of up to 120 kg mol À 1 . Interestingly, the resulting polymers showed narrower band gaps (down to 1.6 eV) than polymers with mono-cycloalkene repeat units due to the planarization of the conjugated segment resulting from the fused bicyclic structure.

cis-Selective Acyclic Diene Metathesis Polymerization Using Bulky Cyclometalated Ruthenium Carbene Catalysts

“…A group of catalysts was evaluated, including G2 ( Ru-1 ) and the “classic” cyclometalated Ru-carbene catalyst Ru-2 bearing a Dipp NHC side arm. We also synthesized the recently developed Ru-3 and Ru-4 featuring a bulkier Dipep side arm and a faster initiation OPh auxiliary, which have been found superior in several challenging CM and cascade polymerization reactions. ,, TONs of these catalysts were first evaluated at low-to-medium conversion using monomer 1 , with a catalyst loading of either 300 or 600 ppm (Figure b). The reactions were monitored until the conversion of terminal double bonds ceased to increase.…”

Designing Degradable Polymers from Tricycloalkenes via Complete Cascade Metathesis Polymerization

“…Olefin metathesis polymerization has been proven to be an efficient strategy for synthesizing polymers via ring‐opening metathesis polymerization (ROMP), [1–11] acyclic diene metathesis (ADMET) polymerization, [12–15] and cyclopolymerization (CP) [16–21] . Additionally, recent development of cascade metathesis polymerizations led to a diverse range of polymers with novel structures and unique properties [22,23] .…”

Functional polydiynes prepared by metathesis cyclopolymerization of 1,7-dihalogen-1,6-heptadiyne derivatives

“…The PAs derived from MCP method demonstrated interesting electrical, optical, and magnetic properties, allowing them to be promising materials for various high-tech applications. [20][21][22][23][24][25][26][27][28][29][30][31][32] For example, M. R. Xie and colleagues explored the intrinsic ionic conductivity and electric conductivity using ionic polyacetylenes as prototype PAs by modification polymer backbones with imidazolium, triazoledendronized or dendritic 1,2,3-triazolium-containing oligo (ethylene glycol) pendants. [20][21][22][23] More recently, they investigated the unique damping properties of block copolymers containing a poly(heptadiyne) and a rubbery segment.…”

“…24 In the same period, T. L. Choi et al focused on searching for narrow/low band gap conjugated PAs through MCP route. 25,26 By cyclopolymerization of rationally designed 1,5-hexadiyne derivatives, the derived PAs contain highly strained cyclobutenes in each repeat unit, and the polymers unexpectedly showed much narrower band gaps than conventional substituted PAs by over 0.2 eV. 25 Recently, they reported a strategy of cascade cyclopolymerization of 5-ethynyl-1,8-nonadiyne derivatives to fabricate narrow band gap conjugated PAs containing fused bicyclic structure, the band gap could be as narrow as 1.6 eV, which was ascribed to the planarization of the conjugated segment resulting from the fused bicyclic structure.…”

“…25 Recently, they reported a strategy of cascade cyclopolymerization of 5-ethynyl-1,8-nonadiyne derivatives to fabricate narrow band gap conjugated PAs containing fused bicyclic structure, the band gap could be as narrow as 1.6 eV, which was ascribed to the planarization of the conjugated segment resulting from the fused bicyclic structure. 26 Certainly, the investigation on the details of MCP mechanism and the development of novel synthetic routes based on MCP are also interesting topics. [27][28][29][30][31] Besides the active research on MCP of terminal diynes and the classical metathesis/insertion polymerization of disubstituted acetylenes, there are also some interesting works on MCP of internal diynes.…”