This report describes the design and synthesis of a new class of polyfurans bearing ester side chains. The macromolecules can be synthesized using catalyst-transfer polycondensation, providing precise control over molecular weight and molecular weight distribution. Such obtained furan ester polymers are significantly more photostable than their alkyl analogues owing to the electron-withdrawing nature of the attached subunit. Most interestingly, they spontaneously fold into a compact π-stacked helix, yielding a complex multilayer cylindrical nanoparticle with a hollow, rigid, conjugated core composed of the polyfuran backbone and a soft, insulating outer layer formed by the ester side chains. The length of polymer side chains dictates the outer diameter of such nanoparticles, which for the hexyl ester groups used in the present study is equal to ∼2.3 nm. The inner cavity of the conjugated core is lined with oxygen atoms, which set its effective diameter to 0.4 nm. Furthermore, installation of bulkier, branched chiral ester side chains on the repeat unit yields structures that, upon change of solvent, can reversibly transition between an ordered chiral helical folded and disordered unfolded state.

Electron-deficient (n-type) conjugated materials are commonly prepared via step-growth methods with limited control over the molecular weight and molecular weight distribution of the resulting polymers. In this communication, we demonstrate that Pd-dialkylbiarylphosphine catalysts enable the chain-growth polymerization of benzo[1,2,3]triazole using Suzuki-Miyaura coupling with molecular weight control and modest molecular weight distributions (Đ ∼ 1.2−1.6). The importance of a free ligand in the reaction mixture during polymerization was established by analysis of polymer samples using GPC and MALDI-TOF mass spectrometry. A block copolymer with poly(3hexylthiophene) was also synthesized by sequential monomer addition. The success of these commercially available catalysts for polymerization of benzotriazole highlights their potential for chain-growth reactions with other bicyclic arenes in the future.

Synthesizing conjugated polymers using controlled polymerization techniques offers tremendous flexibility in the preparation of well-defined semiconducting materials. Suzuki–Miyaura coupling has emerged as a powerful method for these polymerizations since it can be conducted under mild conditions, a range of boron reagents can be employed, and it is exceptionally functional group tolerant. We have analyzed the Ni­(dppp)­Cl2 mediated Suzuki–Miyaura chain-growth polycondensation of 3-hexylthiophene and discovered that a portion of the precatalyst hydrolyzes at the outset of the reaction. Surprisingly, this loss of catalyst is critical to achieving a controlled polymerization as it releases free ligand into the reaction mixture, suppressing chain transfer. The identity of the ligand is also critical, as PPh3 and dppe do not produce the same behavior. Overall, the study offers an improved understanding of conjugated polymer synthesis when using weaker nucleophiles such as boronate esters or boronic acids in Suzuki–Miyaura cross-coupling.

In this report, the synthesis and properties of an ester-functionalized macrocyclic sexifuran (C6FE) are presented.