Aldol Polymerization to Construct Half-Fused Semiconducting Polymers

Abstract

Conventional conjugated polymer synthesis involves costly transition-metal catalysts and even toxic reagents, causing serious environmental challenges around the world. The comonomer linkages of semiconducting polymers are mostly single bonds; charge delocalization and transport have been hindered due to rotation around these single bonds, leading to energetic and conformational disorders. Here, we have developed a novel programmable half-fused polymer library by introducing aldehyde chemistry to promote a very simple and cheap Lewis acid-mediated aldol condensation that affords conjugated polymers with continuous double bonds and single bonds as the linkages between the polymer repeat units, maintaining a coplanar conjugated backbone to eliminate rotation owing to the intramolecular noncovalent interactions. In addition, this innovative concept not only shows an excellent substrate generality but also affords unprecedented polymers with unique properties, allowing us to change the variable conjugated length and side-chain engineering of the backbone to modulate the optoelectronic properties and tune the delocalization of frontier molecular orbitals. These polymers also exhibit very high number-averaged molecular weights (M n ) while showing good solution processability, which makes them applicable as high-performance thin-film transistor materials with reduced conformational disorder. Herein, our results demonstrate that the half-fused design strategy can effectively extend the scope of semiconducting polymers. The low synthetic complexity can be utilized to design organic electronic materials for large-scale production and commercialization.

Highly Efficient Mixed Conduction in N‐type Fused Small Molecule Semiconductors

“…[37,41] NB has become a robust building block for constructing ladder-type rigid polymers and donor-acceptors polymers. [42][43][44][45] Rhodanine is also a strong electron withdrawing unit due to the ketone and thioketone groups on the five-membered aza ring, which have been widely utilized as the terminal groups for non-fullerene acceptors for OPV. [46,47] Herein, to achieve efficient mixed ionic and electronic small molecules conduction in OECTs, we design and synthesize two novel small molecule semiconductors with a highly electron-deficient acceptor-acceptor (A-A) system comprised of lactam and ketone in a favorable fashion.…”

“…[ 37,41 ] NB has become a robust building block for constructing ladder‐type rigid polymers and donor–acceptors polymers. [ 42–45 ] Rhodanine is also a strong electron withdrawing unit due to the ketone and thioketone groups on the five‐membered aza ring, which have been widely utilized as the terminal groups for non‐fullerene acceptors for OPV. [ 46,47 ]…”

Synthesis of isoindigo-derived conjugated polymers via ball-milling metal-free polymerization

“…20,21 In contrast, the emergence of metal-free catalyzed polymerization has offered a promising approach for the synthesis of conjugated polymers (Scheme 1a). [22][23][24][25][26] The acid-catalyzed aldol polymerizations for the synthesis of isoindigo-derived conjugated polymers have gained attention in recent years. [22][23][24][26][27][28][29][30][31] For example, McCulloch and co-workers have reported the p-toluene sulphonic acid-catalysed aldol polymerization for the synthesis of five electron-deficient rigid polymers in good yields.…”

“…[22][23][24][25][26] The acid-catalyzed aldol polymerizations for the synthesis of isoindigo-derived conjugated polymers have gained attention in recent years. [22][23][24][26][27][28][29][30][31] For example, McCulloch and co-workers have reported the p-toluene sulphonic acid-catalysed aldol polymerization for the synthesis of five electron-deficient rigid polymers in good yields. 22 The route is environmentally benign with water as the by-product.…”

Constructing two-dimensional crossed molecular packing through branching chain engineering of amino-indenofluorene derivatives

“…25,26 A common strategy to obtain soluble organic semiconductors is to install flexible alkyl side-chains on the p-conjugated molecular framework. 27,28 Importantly, the incorporation of alkyl side-chains can dramatically affect the charge transport properties of organic semiconductors in the solid state by tailoring the intermolecular interaction and the molecular packing motif. For instance, we have demonstrated that dithiophene-4,9-dione derivatives can exhibit a transition between unipolar and ambipolar charge transport behaviours depending on the length of the side-chains, 29 while attaching heteroatom-linked alkyl chains may increase the carrier mobility up to several orders of magnitude.…”