Sterically demanding binaphthol-based chiral diboranes for metal-free and isotactic poly(propylene oxide)

Chemical Communications, Journal Year: 2023, Volume and Issue: 59(74), P. 11069 - 11072

Published: Jan. 1, 2023

Chiral diborane catalysts based on 3,3′-disubstituted BINOL-backbones, including racemic mixtures thereof, deliver isotactic, semi-crystalline poly(propylene oxide).

Language: Английский

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A Binary Silicon‐Centered Organoboron Catalyst with Superior Performance to That of Its Bifunctional Analogue

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(48)

Published: Oct. 17, 2023

This work reported that a silicon-centered alkyl borane/ammonium salt binary (two-component) catalyst exhibits much higher activity than its bifunctional analogue (one-component) for the ring-opening polymerization of propylene oxide, showing 7.3 times at low loading 0.01 mol %, and even 15.3 an extremely 0.002 %. By using 19 F NMR spectroscopy, control experiments, theoretical calculation we discovered central silicon atom displays appropriate electron density larger intramolecular cavity, which is useful to co-activate monomer deliver propagating chains, thus leading better synergic effect analogue. A unique two-pathway initiation mode was proposed explain unusual high catalytic system. study breaks traditional impression Lewis acid/nucleophilic with poor because increase in entropy.

Language: Английский

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Monomer-controlled self-switchable polymerization: a metal-free strategy for synthesizing multiblock copolymers from epoxides, O-phthalaldehyde, and CO₂

Polymer Chemistry, Journal Year: 2023, Volume and Issue: 14(44), P. 4979 - 4985

Published: Jan. 1, 2023

The preparation of multiblock copolymers is facilitated by monomer-controlled self-switchable terpolymerization.

Language: Английский

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Hybrid anionic block copolymerization: From organocatalysis‐streamlined crossover to internally microphase‐separated aggregates

Aggregate, Journal Year: 2024, Volume and Issue: 5(4)

Published: March 10, 2024

Abstract Polyolefin‐ b ‐poly(ethylene oxide) (PEO) represents the most widely investigated amphiphilic block copolymers. So far, one‐pot continuous synthesis of such hybrid copolymers has only been fulfilled by anionic polymerization through sequential addition vinyl monomers and ethylene oxide (EO). It still remains challenging to achieve altogether high efficiency, molar mass for PEO. Here, we report a copolymerization approach polyisoprene/polystyrene(PI/PS)‐ ‐PEO, in which PI/PS are formed s BuLi‐initiated vinyl‐addition polymerization, then situ employed as macroinitiators ring‐opening (ROP) EO aided an organic Lewis pair. The cooperative (dual‐ion‐complexing) catalytic effect organobase triethylborane is proven, first time, effective lithium alkoxide initiator system, allowing at room temperature ROP activity (complete conversion PEO 3–64 kg/mol reached 1–6 h), narrow distribution, controlled lengths composition. Density functional theory calculation shows that phosphazene bases particularly effective, compared with N ‐heterocyclic bases, complexing Li + enhancing nucleophilicity oxyanion. rate also affected ‐induced aggregation chain‐end ion pairs, though can be offset adequate catalyst loadings. versatility this further demonstrated tri‐/tetrablock ter‐/quaterpolymers constituted PI, PS, PEO, poly(propylene oxide). Of great interest, PS‐ ‐PI‐ ‐PEO triblock terpolymer specific composition found form internally microphase‐separated micellar aggregates when dispersed water.

Language: Английский

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Mesoionic N‐Heterocyclic Olefins as Initiators for the Lewis Pair Polymerization of Epoxides

Macromolecular Rapid Communications, Journal Year: 2024, Volume and Issue: 45(12)

Published: March 18, 2024

Abstract Mesoionic N ‐heterocyclic olefins (mNHOs) have recently emerged as a novel class of highly nucleophilic and super‐basic σ‐donor compounds. Making use these properties in synthetic polymer chemistry, it is shown that combination specific mNHO Mg‐based Lewis acid (magnesium bis(hexamethyldisilazide), Mg(HMDS) 2 ) delivers poly(propylene oxide) quantitative yields from the polymerization corresponding epoxide (0.1 mol% loading). The initiation mechanism involves monomer activation by direct ring‐opening attack mNHO, forming zwitterionic propagating species. Modulation thereby tool to impact efficiency, revealing sterically unencumbered triazole‐derivative particularly useful. joint application mNHOs together with borane‐type acids also outlined, resulting high conversions fast kinetics. Importantly, while molar mass distributions remain relatively broad, indicating faster propagation than initiation, overall masses are significantly lower found case regular NHOs, underlining increased nucleophilicity ensuing improved efficiency mNHOs.

Language: Английский

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