On the Role of Disproportionation Energy in Kumada Catalyst-Transfer Polycondensation

Identifying the missing link in catalyst transfer polymerization

Nickel-catalyzed catalyst transfer polycondensation (CTP) of thiophenes is an efficient strategy for the controlled synthesis of polythiophenes. However, a detailed view of its reaction mechanism has remained elusive with unresolved questions regarding the geometry and bonding of critical Ni(0) thiophene intermediates. Herein, we provide experimental and computational evidence of structurally characterized square planar η2-Ni(0)-thiophene species and their relevance to the mechanism of CTP. These results confirm the viability of C,C-η2 bound intermediates in CTP of thiophenes, providing an electronic rationale for the stability of such species, and thus that such processes can proceed as living polymerizations. We further show that C,S-κ2 species may also be relevant in nickel-catalyzed CTP of thiophenes, providing new avenues for exploitation and optimization.

Catalyst-dependent intrinsic ring-walking behavior on π-face of conjugated polymers

The balance between the ring-walking process and the oxidative-addition state are key determinants of catalyst mobility in catalyst-transfer condensation polymerization.

Thermal Conductance of Poly(3-methylthiophene) Brushes

A wide variety of recent work has demonstrated that the thermal conductivity of polymers can be improved dramatically through the alignment of polymer chains in the direction of heat transfer. Most of the polymeric samples exhibit high conductivity in either the axial direction of a fiber or in the in-plane direction of a thin film, while the most useful direction for thermal management is often the cross-plane direction of a film. Here we show poly(3-methylthiophene) brushes grafted from phosphonic acid monolayers using surface initiated polymerization can exhibit through-plane thermal conductivity greater than 2 W/(m K), a 6-fold increase compared to spin-coated poly(3-hexylthiophene) samples. The thickness of these films (10-40 nm) is somewhat less than that required in most applications, but the method demonstrates a route toward higher thermal conductivity in covalently grafted, aligned polymer films.

Controlled synthesis of high molecular weight poly(3-hexylthiophene)s via Kumada catalyst transfer polycondensation with Ni(IPr)(acac)2 as the catalyst

Ni(IPr)(acac)₂ is a great catalyst for the controlled synthesis of poly(3-hexylthiophene)s with M_ns of 9.90–350 kg mol⁻¹via Kumada catalyst transfer polycondensation.

Intramolecular catalyst transfer polymerisation of conjugated monomers: from lessons learned to future challenges

Eleven years after the first reports on intramolecular catalyst transfer polycondensations, this review aims to critically recap on the fundamental “lessons” that can be learned from the historic literature as well as from the fervid activity that has emerged in the last three years.

Rapid electrochemical reduction of Ni(II) generates reactive monolayers for conjugated polymer brushes in one step

This article reports the development of a robust, one-step electrochemical technique to generate surface-bound conjugated polymers. The electrochemical reduction of arene diazonium salts at the surface of a gold electrode is used to generate tethered bromobenzene monolayers quickly. The oxidative addition of reactive Ni(0) across the aryl halide bond is achieved in situ through a concerted electrochemical reduction of Ni(dppp)Cl2. This technique limits the diffusion of Ni(0) species away from the surface and overcomes the need for solution deposition techniques which often require multiple steps that result in a loss of surface coverage. With this electrochemical technique, the formation of the reactive monolayer resulted in a surface coverage of 1.29 × 10(14) molecules/cm(2), which is a 6-fold increase over previously reported results using solution deposition techniques.

Nickel Catalyst with a Hybrid P, N Ligand for Kumada Catalyst Transfer Polycondensation of Sterically Hindered Thiophenes

A highly active nickel catalyst with a hybrid P,N ligand is successfully used for the first time for the polymerization of a thiophene monomer with sterically very demanding side groups. The performance of this catalyst is by far not achievable with commercially available standard catalysts. Polythiophenes with special side chain patterns can thus be made with predetermined molecular weight, low dispersity, and high regioregularity, which enable the preparation of various large crystalline superstructures for the investigation of anisotropic optoelectronic properties in the absence of π-π interactions.