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

Pollit, Adam A.; Bridges, Colin R.; Seferos, Dwight S.

doi:10.1002/marc.201400482

Cited by 29 publications

(27 citation statements)

References 39 publications

(105 reference statements)

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“…For instance, statistical polymers often result, as observed with dithienosilole and benzotriazole. 51 Other mechanisms, such as chain termination and coupling, still have to be suppressed.…”

Section: Synpacts Syn Lett 5 Electronically Governed Sequence Controlmentioning

confidence: 99%

Electronically Governed ROMP: Expanding Sequence Control for Donor–Acceptor Conjugated Polymers

Koehler¹,

Hu²,

Elacqua³

2020

Synlett

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Controlling the primary sequence of synthetic polymers remains a grand challenge in chemistry. A variety of methods that exert control over monomer sequence have been realized wherein differential reactivity, pre-organization, and stimuli-response have been key factors in programming sequence. Whereas much has been established in nonconjugated systems, π-extended frameworks remain systems wherein subtle structural changes influence bulk properties. The recent introduction of electronically biased ring-opening metathesis polymerization (ROMP) extends the repertoire of feasible approaches to prescribe donor–acceptor sequences in conjugated polymers, by enabling a system to achieve both low dispersity and controlled polymer sequences. Herein, we discuss recent advances in obtaining well-defined (i.e., low dispersity) polymers featuring donor–acceptor sequence control, and present our design of an electronically ambiguous (4-methoxy-1-(2-ethylhexyloxy) and benzothiadiazole-(donor–acceptor-)based [2.2]paracyclophanediene monomer that undergoes electronically dictated ROMP. The resultant donor–acceptor polymers were well-defined (Đ = 1.2, Mn > 20 k) and exhibited lower energy excitation and emission in comparison to ‘sequence-ill-defined’ polymers. Electronically driven ROMP expands on prior synthetic methods to attain sequence control, while providing a promising platform for further interrogation of polymer sequence and resultant properties.1 Introduction to Sequence Control2 Sequence Control in Polymers3 Multistep-Synthesis-Driven Sequence Control4 Catalyst-Dictated Sequence Control5 Electronically Governed Sequence Control6 Conclusions

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Section: Synpacts Syn Lett 5 Electronically Governed Sequence Controlmentioning

confidence: 99%

Electronically Governed ROMP: Expanding Sequence Control for Donor–Acceptor Conjugated Polymers

Koehler¹,

Hu²,

Elacqua³

2020

Synlett

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“…On the basis of these similarities, we previously attempted to generate 1‐pentene/3‐hexylthiophene block copolymers in one pot using diimine‐ligated Ni precatalysts that were known to polymerize olefins via an insertion and chain‐walking mechanism and thiophene via catalyst‐transfer polymerization (CTP) (Chart ) . Although precatalyst C1a was efficient in both homopolymerizations, attempted copolymerization led mostly to homopolymer formation .…”

Section: Introductionmentioning

confidence: 99%

Toward one‐pot olefin/thiophene block copolymers using an in situ ligand exchange

Leone

Dewyer

Kubo

et al. 2019

J. Polym. Sci. Part A: Polym. Chem.

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Block copolymers containing both conducting and insulating segments are of interest due to their enhanced electrical properties arising from their increased crystallization. Yet few methods exist for generating these copolymers, because the reaction conditions for synthesizing each block are often incompatible. Herein, efforts toward identifying a one-pot, living polymerization method for synthesizing block copolymers of 1-pentene and 3-hexylthiophene is described. An in situ ligand exchange enables the optimal catalyst to be utilized for synthesizing each block. Even under these conditions, however, only homopolymers are observed. Computational studies modeling the ligand exchange reveal that the added stabilizing ligands likely inhibit propagation of the second block. These results suggest an ancillary ligand-based "goldilocks" effect wherein catalysts that are stable yet still reactive are required. EXPERIMENTAL Standard Copolymerization ConditionsPrecatalyst C1b (8.2 mg, 0.011 mmol) was dissolved in 1-pentene (0.40 mL) and placed in the freezer (−30 C) for 2 min. Then, while both C1b and tris(pentafluorophenyl) borane (BCF) were still cold, BCF (0.0072 M in 1-pentene, 3.06 mL, 0.0221 mmol, 2.00 equiv) was added to the stirring catalyst, which were stirred for an additional 3 min at rt. Overall [Ni] = 0.0032 M in 1-pentene. Then, THF Additional supporting information may be found in the online version of this article. † These authors contributed equally.

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“…While both Ni and Pd catalysts have been used for poly(olefin) and poly(thiophene) syntheses, we focused on Ni because it out‐performs Pd in the latter case . Diimines were selected as the ancillary ligands for our multitasking catalyst based on their wide use in poly(olefin) synthesis, with recent applications in conjugated polymer synthesis . Both olefin and thiophene enchainment mechanisms involve a Ni(II) intermediate, suggesting that switching from one mechanism to the other may be possible.…”

Section: Introductionmentioning

confidence: 99%

“…23 Diimines were selected as the ancillary ligands for our multitasking catalyst based on their wide use in poly(olefin) synthesis, [24][25][26] with recent applications in conjugated polymer synthesis. [27][28][29][30][31] Both olefin and thiophene enchainment mechanisms involve a Ni(II) intermediate, suggesting that switching from one mechanism to the other may be possible.…”

mentioning

confidence: 99%

Trials and tribulations of designing multitasking catalysts for olefin/thiophene block copolymerizations

Souther

Leone

Vítek

et al. 2017

J. Polym. Sci. Part A: Polym. Chem.

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Block copolymers containing both insulating and conducting segments have been shown to exhibit improved charge transport properties and air stability. Nevertheless, their syntheses are challenging, relying on multiple post-polymerization functionalization reactions and purifications. A simpler approach would be to synthesize the block copolymer in one pot using the same catalyst to enchain both monomers via distinct mechanisms. Such multitasking polymerization catalysts are rare, however, due to the challenges of finding a single catalyst that can mediate living, chain-growth polymerizations for each monomer under similar conditions. Herein, a diimine-ligated Ni catalyst is evaluated and optimized to produce block copolymer containing both 1-pentene and 3-hexylthiophene. The reaction mixture also contains both homopolymers, suggesting catalyst dissociation during and/or after the switch in mechanisms. Experimental and theoretical studies reveal a high energy switching step coupled with infrequent catalyst dissociation as the culprits for the low yield of copolymer. Combined, these studies highlight the challenges of identifying multitasking catalysts, and suggest that further tuning the reaction conditions (e.g., ancillary ligand structure and/or metal) is warranted for this specific copolymerization.

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

Cited by 29 publications

References 39 publications

Electronically Governed ROMP: Expanding Sequence Control for Donor–Acceptor Conjugated Polymers

Electronically Governed ROMP: Expanding Sequence Control for Donor–Acceptor Conjugated Polymers

Toward one‐pot olefin/thiophene block copolymers using an in situ ligand exchange

Trials and tribulations of designing multitasking catalysts for olefin/thiophene block copolymerizations

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