Catalyst-transfer Condensation Polymerization Research Articles

Suzuki–Miyaura Catalyst-Transfer Condensation Polymerization for the Synthesis of Polyphenylene with Ester Side Chain by Using Stable, Reactive 1,1,2,2-Tetraethylethylene Glycol Boronate (B(Epin)) Monomer

Suzuki–Miyaura Catalyst-Transfer Condensation Polymerization for the Synthesis of Polyphenylene with Ester Side Chain by Using Stable, Reactive 1,1,2,2-Tetraethylethylene Glycol Boronate (B(Epin)) Monomer

Tandem Kumada-Tamao catalyst-transfer condensation polymerization and Suzuki-Miyaura coupling for the synthesis of end-functionalized poly(3-hexylthiophene).

Successive Kumada-Tamao catalyst-transfer condensation polymerization of 2-bromo-5-chloromagnesio-3-hexylthiophene and Suzuki-Miyaura end-functionalization with pinacol arylboronate in one pot afforded poly(3-hexylthiophene) (P3HT) with a base-sensitive functional group at both ends. The use of poly(methyl methacrylate) (PMMA) bearing a boronic acid ester moiety at one end enabled one-pot synthesis of PMMA-b-P3HT-b-PMMA triblock copolymer.

Precision synthesis of a fluorene-thiophene alternating copolymer by means of the Suzuki–Miyaura catalyst-transfer condensation polymerization: the importance of the position of an alkyl substituent on thiophene of the biaryl monomer to suppress disproportionation

The Suzuki–Miyaura coupling polymerization of PinB-F8T(3)-Br was accompanied by disproportionation, whereas that of PinB-F8T(4)-Br proceeded in a chain-growth polymerization manner to afford a well-defined fluorene-thiophene alternating copolymer.

Effect of the Nature and the Position of Defects on the Chiral Expression in Poly(3-alkylthiophene)s

Polymers produced with the most used controlled polymerization method with the simplest initiators, namely the Kumada catalyst transfer condensation polymerization (KCTCP) with Ni2+ salts, all have one regiodefect distributed along the polymer backbones. The irregularity created by these defects can be split up into three components, i.e., the nature of the defect, the position of the defect, and the additional inhomogeneity created by mixing polymers with the defect at different positions. In this research, the influence of these three parameters on the chiral expression of poly(3-alkylthiophene)s (P3ATs) is investigated separately for the first time. A series of chiral P3ATs with one tail-to-tail (TT) or head-to-head (HH) defect in different positions is synthesized by means of the Pd(RuPhos) protocol, and their chiral expression and that of their mixtures are studied via UV–vis and circular dichroism (CD) spectroscopy. For the polymers with an HH defect, it is found that the position at the very beginning of the polymer chain is the most optimal to obtain the largest chiral expression, and the obtained signal is even the highest ever reported for PTs in chloroform and MeOH solutions. When a TT defect is incorporated into the polymer, the chiral expression is much weaker, and the most optimal position of the defect is a little shifted toward the middle of the chain compared to their HH analogues. For the mixtures of the polymers with an HH defect, a weighted average of the signals of its constituents is obtained, but for the mixtures of the polymers with a TT defect different results are obtained. When 25% of each polymer is mixed, no chiral response is obtained, and when more of the polymers with the defect more toward the chain ends are incorporated, a chiral response higher than that of any of the component polymers is recorded. This shows that the chiral expression is not only influenced by the nature or the position of a defect, but also by the mixing of polymers with a defect in different positions.

Insights in the Ni-thiophene association in the synthesis of thiophene-para-phenylene block copolymers via Kumada catalyst transfer condensative polymerization

In this article we investigate association of the Ni-catalyst during Kumada catalyst transfer condensative polymerization (KCTCP) and hypothesize that when adding a para-phenylene monomer to a living thiophene block to synthesize poly(thiophene)-b-poly(para-phenylene), an equilibrium exist between the incorporation of the para-phenylene monomer and the trapping of the Ni-catalyst by association with the thiophene block. We suggest that this equilibrium shifts toward the association with the thiophene block with increasing length of the thiophene block and that significant trapping only occurs when this block consist of several thiophene units.

Rational Design of Poly(fluorene)-b-poly(thiophene) Block Copolymers to Obtain a Unique Aggregation Behavior

In poly(thiophene) (PT) block copolymers, aggregation features can be transferred from one block to the other. In this paper, it is investigated whether this is also possible in block copolymers consisting of blocks with different electronic properties, i.e. PT and poly(fluorene) (PF), in order to obtain a polymer with a unique combination of aggregation properties. By combining a PT block with chiral side chains with a PF block with linear octyl side chains, it is probed to obtain a polymer in which chiral expression (arising from the PT with chiral side chains) and β-phase aggregation (arising from the PF with linear octyl side chains) are brought together. This combination is not possible in homopolymers, since chiral aggregation implies chiral, branched side chains and β-phase aggregation is only possible for PF with linear side chains. In a stepwise approach, the right conditions are elucidated to obtain both characteristics in one polymer. For this purpose, three block copolymers were synthesized via Suzuki catalyst transfer condensative polymerization (SCTCP), i.e. , poly(9,9-dioctylfluorene)-b-poly(3-((S)-3,7-dimethyloctyl)thiophene) (POF-b-P3OT*), poly(9,9-dihexylfluorene)-b-poly(3-((S)-3,7-dimethyloctyl)thiophene) (PHF-b-P3OT*), and poly(9,9-dioctylfluorene)-b-poly(3-((S)-2-methylbutyl)thiophene) (POF-b-P3BT*), and their aggregation behavior was studied via solvatochromism experiments. It is concluded that the side chains of the PF block should be 8 C atoms long to ensure maximal β-phase aggregation and that the side chains of the PT block should be short to ensure this block aggregates first in a chiral way. In this way, the PT block can transfer its chirality to the PF block and a polymer is obtained in which β-phase aggregation and expression of chirality are combined in one PF, something which is impossible for homopolymers.

Controlled Polymerization of a Cyclopentadithiophene–Phenylene Alternating Copolymer

The new conjugated poly(4,4-bis(2-ethylhexyl)cyclopentadithiophene-alt-p-phenylene) (PCPDTPP) has been synthesized in a controlled way via catalyst transfer condensative polymerization (CTCP) of the corresponding biaryl monomer. Therefore, a series of Ni catalysts as well as (new) Pd-PEPPSI catalysts were employed in different Kumada CTCPs (KCTCPs) and Negishi CTCPs (NCTCPs). A series of tests confirmed the absence of undesired transfer and termination reactions and, hence, the controlled character of the chain-growth polymerization with Ni(dppe)Cl2 as catalyst. This resulted in polymers with low dispersities (Đ = 1.2), Mn of 33 kDa, and relatively good end-group control. Furthermore, formation of PCPDTPP-b-poly(3-octylthiophene) (P3OT) block copolymers was possible. Via optical analysis and DSC measurements, we demonstrated that the conjugated alternating PCPDTPP copolymer is an amorphous, strongly fluorescent polymer with a fluorescence quantum yield (ϕf) of 58% in chloroform.

Influence of the Sequence in Conjugated Triblock Copolymers on Their Aggregation Behavior

Conjugated diblock copolymers can exhibit very promising properties, often based on microphase separation. However, both blocks can influence each other’s aggregation behavior, which might lead to a suboptimal aggregation behavior of the consecutive blocks. Herein, we investigate whether the introduction of a third, nonaggregating block can render triblock copolymers where the two blocks do not influence the aggregation behavior of one another. Different triblock copolymers consisting of solely thiophene units as well as triblock copolymers containing selenophene and (a)chiral thiophene units were designed to investigate the influence of the sequence of the blocks, the initiating unit, and the nonaggregating block on the aggregation behavior of the resulting triblock copolymers. The conjugated triblock copolymers were synthesized via a controlled Kumada catalyst transfer condensative polymerization (KCTCP), and their aggregation behavior was investigated via UV–vis and circular dichroism (CD) spectroscopy. For all synthesized polymers it was observed that when two aggregating blocks are separated from each other by a nonaggregating block, they do not influence each other’s aggregation behavior and aggregate separately. However, when the two aggregating blocks are situated next to each other, they influence each other’s aggregation behavior strongly and aggregate as one block.

Catalyst‐Transfer Suzuki–Miyaura Condensation Polymerization of Stilbene Monomer: Different Polymerization Behavior Depending on Halide and Aryl Group of ArPd(tBu3P)X Initiator

ABSTRACTWe report Suzuki–Miyaura coupling polymerization of tetraalkoxy‐substituted 4‐bromostilbene‐4′‐boronic acid 1 with several t‐Bu3P‐ligated Pd initiators; this is the first example of catalyst‐transfer condensation polymerization (CTCP) of a monomer containing a carbon–carbon double bond. When o‐tolylPd(tBu3P)Br was used as the initiator, the o‐tolyl group was not introduced at the polymer end, but polymer with boronic acid at one end and bromine at the other was obtained. However, when we employed stilbenePd(tBu3P)I generated in situ from iodostilbene and Pd(tBu3P)G2 precatalyst, or isolated ArPd(tBu3P)X (Ar, X = Ph, I; o‐tolyl, I; and Ph, Br), the aryl group was introduced at the polymer end, indicating that CTCP of 1 proceeded. Therefore, the iodide and aryl group of the Pd initiator complex is crucial for CTCP of 1. However, the molecular weight distribution of the obtained polymer was broad, possibly because coordination of the carbon–carbon double bond of 1 to ArPd(tBu3P)I resulted in slow initiation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 297–304

Controlled Synthesis of a Helical Conjugated Polythiophene

Two new polymer systems, poly(3-phenylenevinylene)thiophene (P3PVT) and poly(3-phenyl)thiophene (P3PT), were designed with the aim of obtaining a helical conjugated polymer via a living polymerization. The polymerization proceeded without transfer and termination reactions via the Kumada catalyst transfer condensative polymerization (KCTCP) mechanism, confirming the living nature of the polymerization. Solvatochroism and circular dichroism (CD) experiments showed the helical nature of P3PVT and the stacking behavior of P3PT in poor solvent conditions. Block copolymers of 3-alkyl-substituted polythiophenes and helical P3PVT were prepared to determine the aggregation behavior of such systems. Solvatochroism, CD, and AFM measurements showed that the blocks influence each other’s behavior. If the P3AT block stacks before the helical P3PVT block organizes, one-handed helix formation is hindered. If helix formation occurs first, the stacking behavior is not influenced.

The Influence of Substituents in the 3‐Position on the Polymerization of Metaphenylenes

AbstractIn this manuscript, the influence of the position of the alkoxy‐substituents on the polymerization of poly(phenylenes) is investigated. For this purpose, 3‐alkoxy‐m‐phenylene is polymerized using the Kumada catalyst transfer condensative polymerization. Three different catalyst systems are tried, which all resulted in polymer, but with a high dispersity. Additional experiments show that the polymerization proceeds via a noncontrolled chain growth mechanism.

AmPhos Pd-Catalyzed Suzuki–Miyaura Catalyst-Transfer Condensation Polymerization: Narrower Dispersity by Mixing the Catalyst and Base Prior to Polymerization

Several palladium catalysts with bulky phosphine ligands other than t-Bu3P were investigated for Suzuki–Miyaura catalyst-transfer condensation polymerization (CTCP). When the model reaction of 2,5-dibromothiophene with phenylboronic acid ester was carried out with a variety of Pd precatalysts in the presence of K3PO4 as a base, we found that the use of di-tert-butyl(4-dimethylaminophenyl)phosphine (AmPhos) Pd as a precatalyst resulted in exclusive formation of diphenyl-substituted thiophene. Polymerization of thiophene monomer and fluorene monomer with an initiator generated in situ from AmPhos Pd precatalyst and 4-iodobenzonitrile proceeded via the CTCP mechanism, affording polythiophene (P3HT) and polyfluorene with low dispersity and controlled polymer ends. Furthermore, (tolyl)PdAmPhos(Br) (7) was synthesized, and its polymerization properties were investigated. We found that polymerization of thiophene monomer with a mixture of 7 and CsF that had been stirred for 1 h prior to polymerization afforded P...

Conjugated ionic (co)polythiophene-based cathode interlayers for bulk heterojunction organic solar cells

The incorporation of conjugated polyelectrolytes as cathode interlayers in organic photovoltaics has been proven to be an effective way to boost the device efficiency. Nevertheless, more detailed investigations of the structure–property relationships of these interlayer materials, in particular related to the film deposition behavior, can provide further insights into their mode of action. With this aim, a series of ionic (co)polythiophenes is successfully synthesized via Kumada catalyst-transfer condensation polymerization and subsequent introduction of ionic moieties on the polymer side chains. Both the topology (i.e. homopolymers, random and block copolymers) and the amount of ionic groups are systematically varied. The polymers are fully characterized and then applied as cathode interlayers in polymer solar cells based on PCDTBT:PC71BM, affording an average efficiency increase of ∼15%. The structural screening on one hand indicates that the efficiency gain is a rather general phenomenon for this material class. On the other hand, the best photovoltaic responses are observed for the conjugated polyelectrolytes with a higher triethylene glycol side chain ratio and the block copolymer structure performs slightly better as compared to the random copolymer with the same (50/50) monomer ratio. Based on these findings, the field can move on to a more rational development of novel interfacial materials and thereby push the device efficiency even further.

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.

The influence of branching on the Kumada catalyst transfer condensative polymerization of 3-alkylthiophenes

The influence of branching of the substituent in polythiophenes on the rate and the livingness of the polymerization is discussed.

Mechanistic Investigation of Catalyst-Transfer Suzuki-Miyaura Condensation Polymerization of Thiophene-Pyridine Biaryl Monomers with the Aid of Model Reactions.

We have investigated the requirements for efficient Pd-catalyzed Suzuki-Miyaura catalyst-transfer condensation polymerization (Pd-CTCP) reactions of 2-alkoxypropyl-6-(5-bromothiophen-2-yl)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (12) as a donor-acceptor (D-A) biaryl monomer. As model reactions, we first carried out the Suzuki-Miyaura coupling reaction of X-Py-Th-X' (Th=thiophene, Py=pyridine, X, X'=Br or I) 1 with phenylboronic acid ester 2 by using tBu3 PPd0 as the catalyst. Monosubstitution with a phenyl group at Th-I mainly took place in the reaction of Br-Py-Th-I (1 b) with 2, whereas disubstitution selectively occurred in the reaction of I-Py-Th-Br (1 c) with 2, indicating that the Pd catalyst is intramolecularly transferred from acceptor Py to donor Th. Therefore, we synthesized monomer 12 by introduction of a boronate moiety and bromine into Py and Th, respectively. However, examination of the relationship between monomer conversion and the Mn of the obtained polymer, as well as the matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra, indicated that Suzuki-Miyaura coupling polymerization of 12 with (o-tolyl)tBu3 PPdBr initiator 13 proceeded in a step-growth polymerization manner through intermolecular transfer of the Pd catalyst. To understand the discrepancy between the model reactions and polymerization reaction, Suzuki-Miyaura coupling reactions of 1 c with thiopheneboronic acid ester instead of 2 were carried out. This resulted in a decrease of the disubstitution product. Therefore, step-growth polymerization appears to be due to intermolecular transfer of the Pd catalyst from Th after reductive elimination of the Th-Pd-Py complex formed by transmetalation of polymer Th-Br with (Pin)B-Py-Th-Br monomer 12 (Pin=pinacol). Catalysts with similar stabilization energies of metal-arene η2 -coordination for D and A monomers may be needed for CTCP reactions of biaryl D-A monomers.

Catalyst‐Transfer Condensation Polymerization of Acceptor Aromatic Monomers and of Donor Carbon‐Carbon Double Bond‐Containing Monomers

SummaryRecent developments in catalyst‐transfer condensation polymerization (CTCP), which proceeds in a chain‐growth polymerization manner, have made it possible to synthesize well‐defined π‐conjugated polymers with controlled molecular weight and low polydispersity, as well as block copolymers and gradient copolymers. However, CTCP has been limited to the polymerization of donor monomers (such as thiophene) for the synthesis of p‐type π‐conjugated polymers. Here, we highlight several recent advances in CTCP of acceptor aromatic monomers and monomers conjugated with carbon‐carbon double bond, the π‐donation ability of which is stronger than donor aromatic rings. In the former polymerization, well‐defined poly(pyridine‐3,5‐diyl), poly(benzotriazole), poly(fluorene‐alt‐benzothiaziazole), and poly(bithiophene‐alt‐naphthalene diimide) were obtained. In the latter polymerization, however, the obtained poly(p‐phenylenevinylene) possessed broad molecular weight distribution.

Investigation of Mizoroki-Heck coupling polymerization as a catalyst-transfer condensation polymerization for synthesis of poly(p-phenylenevinylene)

Mizoroki-Heck coupling polymerization of 1,4-bis[(2-ethylhexyl)oxy]-2-iodo-5-vinylbenzene (1) and its bromo counterpart 2 with a Pd initiator for the synthesis of poly(phenylenevinylene) (PPV) was investigated to see whether the polymerization proceeds in a chain-growth polymerization manner. The polymerization of 1 with tBu3PPd(Tolyl)Br (10) proceeded even at room temperature when 5.5 equiv of Cy2NMe (Cy = cyclohexyl) was used as a base, but the molecular weight distribution of PPV was broad. The polymerization of 2 hardly proceeded at room temperature under the same conditions. In the polymerization of 1, PPV with H at one end and I at the other was formed until the middle stage, and the polymer end groups were converted into tolyl and H in the final stage. The number-average molecular weight (Mn) did not increase until about 90% monomer conversion and then sharply increased after that, indicating conventional step-growth polymerization. The occurrence of step-growth polymerization, not catalyst-transfer chain-growth polymerization, may be interpreted in terms of low coordination ability of H-Pd(II)-X(tBu3P) (X = Br or I), formed in the catalytic cycle of the Mizoroki-Heck coupling reaction, to π-electrons of the PPV backbone; reductive elimination of H-X from this Pd species with base would take place after diffusion into the reaction mixture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 543–551

Investigation of catalyst-transfer condensation polymerization for synthesis of poly(p-phenylenevinylene)

Investigation of catalyst-transfer condensation polymerization for synthesis of poly(<i>p</i>-phenylenevinylene)

ChemInform Abstract: Scope of Controlled Synthesis via Chain‐Growth Condensation Polymerization. From Aromatic Polyamides to π‐Conjugated Polymers

AbstractReview: 159 refs.