Modulating the Rate of Controlled Suzuki–Miyaura Catalyst-Transfer Polymerization by Boronate Tuning

Abstract

Despite the remarkable breakthroughs in the catalyst-transfer polymerization (CTP) technology in the precision synthesis of conjugated polymers, modulating the monomer reactivity is still challenging. We report that, by boronate tuning, we can modulate the rate of the Suzuki–Miyaura CTP (SCTP) of 3-hexylthiophene with high control. First, cyclic boronate esters showed different polymerization rates depending on their diol subunit structure. Additionally, the rates of the N-coordinated boronates were differentiated by tuning their O- or N-substituents. Notably, the origin of the difference in reactivity could be explained by the N → B bond lengths. The detailed structural analysis of the resulting polymers by 1H nuclear magnetic resonance (NMR) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) spectrometry showed that the slower and more stable boronate monomers were less prone to homocoupling and protodeboronation, thereby producing poly­(3-hexylthiophene) (P3HT) with higher control (i.e., molecular weight, dispersity, end-group fidelity, and yield). By rational optimizations to suppress homocoupling and protodeboronation, well-defined P3HT were prepared at various monomer-to-initiator ratios (M/I ratios).

N-Coordinated Organoboron in Polymer Synthesis and Material Science

“…The reaction rates of various boronate esters were also compared for Suzuki–Miyaura catalyst-transfer polymerization, thereby showing that the length of the N→B dative bond illustrated the origin of the difference in reactivity via density functional theory (DFT) calculations, which might give us enlightenment to affect the performance by constructing the chemical structures.…”

“…Moreover, the living Suzuki−Miyaura catalysttransfer polymerization was used for synthesizing various donor−acceptor alternating conjugated polymers, which exhibited a tunable optical band gap and highest occupied molecular orbital (HOMO) level. 57 The reaction rates of various boronate esters were also compared for Suzuki−Miyaura catalyst-transfer polymerization, thereby showing that the length of the N→B dative bond illustrated the origin of the difference in reactivity via density functional theory (DFT) calculations, 25 which might give us enlightenment to affect the performance by constructing the chemical structures.…”

“…The lone pair electrons of nitrogen will further destabilize the adjacent carbon radicals. , (2) At neutral pH, the binding of diols and boronic acids is strongly enhanced with the N→B interactions. Strong binding typically requires pH values above 9, whereas it can exist over a broad pH range of approximately 5 to 11 with the N→B interactions. − (3) The homologous coupling and deboronation of boronic acids or esters may be suppressed since the N→B dative bond can protect the active boronate esters. , (4) Charge transfer can be achieved by boron acting as an electron acceptor and nitrogen as an electron donor …”

“…The homologous coupling and deboronation of boronic acids or esters may be suppressed since the N→B dative bond can protect the active boronate esters. 25,26 (4) Charge transfer can be achieved by boron acting as an electron acceptor and nitrogen as an electron donor. 27 With the assistance of electron donors, the N-coordinated organoborons exhibit unique properties.…”

Living Suzuki–Miyaura Catalyst-Transfer Polymerization for Precision Synthesis of Length-Controlled Armchair Graphene Nanoribbons and Their Block Copolymers

“…37−42 Furthermore, the stability and reactivity of the monomers were also tuneable by rational design of boronates, thereby improving SCTP controllability. 43,44 As results of both features, the scope of (hetero)arene monomers greatly expanded exceeding that of other conventional catalysts. 37−39 Herein, we report the precise synthesis of length-controlled and structurally well-defined armchair GNRs (AGNRs) using SCTP (Figure 1c).…”