Mononuclear Salen–Sodium Ion Pairs as Catalysts for Isoselective Polymerization of <i>rac</i>-Lactide

Cui, Yaqin; Jiang, Jinxing; Mao, Xiaoyang; Wu, Jincai

doi:10.1021/acs.inorgchem.8b02290

Cited by 29 publications

(19 citation statements)

References 71 publications

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“…The only one set of series of signals of linear PMA clearly exhibits that no cyclization reaction exists in this system. Based on the aforementioned experimental results, the ROP of manOCA may proceed via a ligand-assisted activated monomer mechanism − (Figures and S27), which can also be verified by density functional theory (DFT) calculations at the M062x/6-31+G(d, p) level with the pseudopotential basis set of SDD for the zinc atom ( t -butyl groups of phenol at the para-position were replaced with hydrogen atoms, and methanol was used as alcohol for reducing the calculation time). First, the monomer of manOCA can be activated by the coordination to the zinc atom, and alcohol can be activated by the hydrogen-bond interaction with the phenoxide group in complex 1 .…”

Section: Resultssupporting

confidence: 82%

Living Polymerization of Chiral O-Carboxyanhydride of Mandelic Acid and Precise Stereoblock Copolymer Syntheses Using Highly Active OOO-Tridentate Bis(phenolate) Zinc Complexes

et al. 2021

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The synthesis of highly stereoregular poly(mandelic acid) (PMA) via controllable polymerization is a considerable challenge because of the easy racemization of monomers during polymerization; consequently, precise stereoblock copolymers of PMA have not been reported so far. In this work, highly stereoregular PMA was synthesized through a living ring-opening polymerization of O-carboxyanhydrides (OCAs) of mandelic acid using highly active OOO-tridentate bis(phenolate)/zinc catalysts. In this polymerization system, the side reaction of racemization was suppressed very well via decreasing the basicity of ligands in zinc complexes. The molecular weight increases linearly as the ratio of monomer to initiator increases and can be high up to 32.5 kg/mol with narrow molecular weight distributions. Meanwhile, for the living polymerization feature, stereodiblock and stereotriblock copolymers with controllable molecular weights were obtained upon sequential one-pot monomer addition within 45 min. Thermal and X-ray diffraction characterizations indicated that these stereoblock copolymers crystallized in a stereocomplex phase with a distinct melting temperature (T m) up to 178 °C, and the solubility behaviors of stereoblock PMAs and enantiomeric homopolymers of PMAs are remarkably different.

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Section: Resultssupporting

confidence: 82%

Living Polymerization of Chiral O-Carboxyanhydride of Mandelic Acid and Precise Stereoblock Copolymer Syntheses Using Highly Active OOO-Tridentate Bis(phenolate) Zinc Complexes

et al. 2021

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“…Moreover, 1 H NMR spectrum of rac ‐LA polymerized by rac1 showed no observance of a weak quartet peak at 5.07 ppm and a doublet peak at 1.72 ppm, which suggest no epimerization occurred (Figure S23, Supporting Information). [ 14a,b ]…”

Section: Methodsmentioning

confidence: 99%

Highly Isoselective Ring‐Opening Polymerization of rac‐Lactide Using Chiral Binuclear Aluminum Catalyst

Wan

Bai

et al. 2020

Macromol. Rapid Commun.

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The microstructure can significantly affect the physical and mechanical properties of polymers. Five chiral binuclear aluminum methyl complexes (rac1 to rac5) are synthesized by using chiral binaphthalene diamine ligand and characterized by both 1H and 13C NMR spectroscopy. The crystal structures of rac3 and rac5 are also identified by single crystal X‐ray diffraction. In the presence of iPrOH initiator, these aluminum complexes catalyze the ring‐opening polymerization (ROP) of rac‐lactide (rac‐LA) in a controlled manner and produce polymers with high to excellent isoselectivity (Pm up to 0.93). Even with a catalyst loading as low as 0.1%, polylactide with a Pm of 0.83 can still be obtained. Kinetic studies reveal the first‐order dependence on monomer concentration whereas kinetic resolution polymerization provides the evidence to support that these binuclear aluminum catalysts catalyzed ROP of rac‐LA adopts enantiomorphic site control mechanism. Furthermore, this strategy can also be applied to the ROP of both ε‐caprolactone and δ‐valeroactone.

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“…When THF and CH 2 Cl 2 were used as solvents, the epimerization side reaction of L -lactide ( L -LA) exists clearly in the ROP process at room temperature (Table 1, entries 1 and 2) which can be proved by the 1 H NMR spectrum signals of meso-lactide at 5.07 and 1.72 ppm (Figures S29A,B). 52,[55][56][57] Using toluene as a solvent, the epimerization of L -LA decrease remarkably in the ROP process at room temperature (Table 1, entry 3, Figure S29C), possibly due to the less polar nature of toluene and faster ROP process than the epimerization. Comparatively, complex 1 exhibited a high catalytic activity for the ROP of L -LA with a 400/1/4 ratio of [ L -LA] 0 /[Cat] 0 /[BnOH] 0 in toluene at room temperature, and the conversion of monomer can reach 74% within 30 s (Table 1, entry 3).…”

Section: Living and Isoselective Rop Of Rac-la Under Anhydrous Condit...mentioning

confidence: 99%

Bench‐stable potassium complexes for living and isoselective ring‐opening polymerization of rac‐lactide

Ren

Xian

et al. 2022

Journal of Polymer Science

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To develop bench‐stable and nontoxic catalysts for the ring‐opening polymerization (ROP) of lactides is of importance with the aim of reducing costs in industrial production. Although, recently, some potassium complexes have been reported for the living polymerization of rac‐lactide (rac‐LA), the moisture sensitivities of these complexes prevent their further applications in the mild polymerization condition. In this work, three bench‐stable potassium phenolates as isoselective catalysts for the ROP of rac‐LA were reported, and the moisture stability of these complexes does not inhibit their high activity under mild conditions even in the presence of trace water (2.0 equivalent relative to the catalysts) or unpurified solvents. The controllable polymerization reactions can afford polylactides with desirable molecular weights, which can be high up to Mn = 80.0 kg/mol at an anhydrous condition and Mn = 54.3 kg/mol in presence of trace water. A best isoselectivity of Pm = 0.83 also can be achieved in this system at −70°C.

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Mononuclear Salen–Sodium Ion Pairs as Catalysts for Isoselective Polymerization of rac-Lactide

Cited by 29 publications

References 71 publications

Living Polymerization of Chiral O-Carboxyanhydride of Mandelic Acid and Precise Stereoblock Copolymer Syntheses Using Highly Active OOO-Tridentate Bis(phenolate) Zinc Complexes

Living Polymerization of Chiral O-Carboxyanhydride of Mandelic Acid and Precise Stereoblock Copolymer Syntheses Using Highly Active OOO-Tridentate Bis(phenolate) Zinc Complexes

Highly Isoselective Ring‐Opening Polymerization of rac‐Lactide Using Chiral Binuclear Aluminum Catalyst

Bench‐stable potassium complexes for living and isoselective ring‐opening polymerization of rac‐lactide

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