One-Pot Synthesis of All-Conjugated Block-Like Bisthiophene–Naphthalenediimide/Fluorene Copolymer

Abstract

A copolymerization of electron-rich and electrondeficient monomers via the chain-growth catalyst-transfer polycondensation route is highly challenging and has never been accomplished thus far, to the best of our knowledge. Herein, we report a simple method to copolymerize two monomers of a significantly different nature: anion-radical naphthalene diimide−dithiophene-based and zinc-organic ABtype fluorenic ones. We found that the copolymerization proceeds rapidly in the presence of Pd catalyst having the bulky and electron-rich tri-tert-butylphosphine ligand. Despite the fact that the two monomers are simultaneously added to the copolymerization (batch polymerization), the polymerization leads to a gradient or even block-like copolymer rather than to a random copolymer or to a mixture of homopolymers, as evident from NMR, GPC, AFM, and fluorescence quenching experiments. The block-like copolymer is formed because the fluorenic monomer polymerizes much faster, yet because the resulting PF2/6 homopolymer is able to initiate polymerization of the second monomer, presumably acting as macroinitiator. Although the investigated copolymerization does not involve a living propagation mechanism and the resulting product is not a well-defined block copolymer, this result is an important step toward a general protocol for preparation of all-conjugated donor− acceptor block copolymers for optoelectronic applications.

Role of Solution Structure in Self-Assembly of Conjugated Block Copolymer Thin Films

“…2D SAXS scattering patterns were acquired by transmission of a 14 keV beam through a temperature-controlled liquid flow cell and azimuthally integrated to obtain line profiles (Figure 2). 48 As the temperature is decreased towards room temperature from 80 °C where the block copolymer is dissolved, aggregation becomes increasingly pronounced. A weak scattering peak, centered at a scattering vector of 3.0 nm -1 , which is similar to (100) spacing of crystalline DPPT-T or P3HT in the solid, 66 is increasingly observed as the solution ) and sheets or discs (q -2 ).…”

“…This goal has been met by BCPs where either one block has a conjugated backbone and the other has an insulating backbone with pendant conjugated molecules, [29][30][31][32][33][34][35][36][37] or by structures where both blocks have conjugated backbones (CBCPs). [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] Because of the relative stiffness of conjugated backbones, the phase separation of their BCP is complex due to energetic interactions between blocks, the volume fraction of the blocks, and potential crystallization.…”

Block Junction-Functionalized All-Conjugated Donor–Acceptor Block Copolymers

“…Only a few examples of all-conjugated, D-A BCPs made by chain growth polymerization have been disclosed. 22,23 The foremost alternative synthetic approach makes use of narrowly distributed poly(3-hexylthiophene) P3HT with well-defined and controllable end group chemistry as a macroreagent. [24][25][26][27][28][29] To this end, the judicious choice of building blocks and synthetic chemistry can be used to generate different molecular connectivity at the block junction.…”

Evidence for the Chain-Growth Synthesis of Statistical π-Conjugated Donor-Acceptor Copolymers

“…[21][22][23][24][25][26][27][28][29] In this way, molecular weight and dispersity are well controlled, along with polymer composition and end-group functionality. Until recently, chain-growth polymerization has been limited to a small number of electron-defi cient monomers, [30][31][32][33][34] however the implementation of a Ni(II) diimine catalyst by our group has expanded the scope of monomers available to include both electron rich and defi cient. [ 35 ] Very recently we have utilized Ni(II) diimine catalysts to prepare donor-acceptor block copolymers, demonstrating the controlled incorporation of both electron rich and defi cient moieties on a single polymer chain.…”