Computational Prediction and Experimental Verification of ε-Caprolactone Ring-Opening Polymerization Activity by an Aluminum Complex of an Indolide/Schiff-Base Ligand

Mandal, Mukunda; Luke, Anna M.; Dereli, Büşra; Elwell, Courtney E.; Reineke, Theresa M.; Tolman, William B.; Cramer, Christopher J.

doi:10.1021/acscatal.8b04540

Cited by 22 publications

(20 citation statements)

References 32 publications

(24 reference statements)

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“…There is no doubt that the metal-based catalysts are dominant in the polymerization catalysis area, given their varying combinations of ligands and metals. In the past decades, a variety of aluminum, − magnesium and zinc, − iron, titanium, and zirconium, − and rare-earth-metal − complexes have been employed for the preparation of polyesters. Among these, Al complexes ligating ancillary ligands have gained considerable attention and have become promising candidates for ROP reactions due to their high activity, relatively low toxicity, and good control of the molecular weight (MW) and dispersity ( Đ = M w / M n ) of the resulting polyesters .…”

Section: Introductionmentioning

confidence: 99%

Aluminum Complexes Bearing Bidentate Amido–Phosphine Ligands for Ring-Opening Polymerization of ε-Caprolactone: Steric Effect on Coordination Chemistry and Reactivity

et al. 2019

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The aluminum complexes LAlMe2 (Al1–Al5: LH = 2,6-(R1)2-4-R2-C6H2NHCH2C6H4-2-PPh2; Al1, R1 = H, R2 = H; Al2, R1 = Me, R2 = H; Al3, R1 = i Pr, R2 = H; Al4, R1 = Ph2CH, R2 = i Pr; Al5, R1 = Cl, R2 = H) have been synthesized and characterized by elemental analysis and 1H, 13C, and 31P NMR. NMR analysis in solution reveals an interesting hemilabile coordination of the soft P donor. The molecular structures of Al2–Al4 were defined by X-ray diffraction studies, showing a distorted-tetrahedral geometry around the aluminum center in all structures. Careful comparison of these crystal structures suggested that different substituents on the ligands could lead to unignorable changed coordination environments around the Al center, thus affecting their catalytic properties. In the presence of BnOH, complexes Al1–Al5 efficiently catalyzed the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) with high conversions in a controlled manner, and high molecular weights (M n up to 118.6 kg mol–1) of polycaprolactones (PCLs) were readily prepared. Immortal polymerizations by Al4 having bulky Ph2CH groups were also studied with up to 20 equiv of alcohols and 2000 equiv of monomers, without sacrificing polymerization control.

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Section: Introductionmentioning

confidence: 99%

Aluminum Complexes Bearing Bidentate Amido–Phosphine Ligands for Ring-Opening Polymerization of ε-Caprolactone: Steric Effect on Coordination Chemistry and Reactivity

et al. 2019

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“…This overcomes monomer solubility challenges during the polymerization. We predicted polymerizations of R -BC with bulky aluminum–salen complexes [( TBS-salen ) Al-OBn and ( Ad-salen ) Al-O i Pr ] could yield regioselectivity in the polymerization as well. ,,,− Given the usefulness of the aluminum complexes in preparing isotactic PLA, the compatibility of the aluminum complexes with R -BC adds another attractive feature for exploring these catalysts (Scheme ).…”

Section: Results and Discussionmentioning

confidence: 99%

Regioregular Polymers from Biobased (R)-1,3-Butylene Carbonate

et al. 2021

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We present (R)-1,3-butylene carbonate ( R-BC) as a biorenewable monomer for the preparation of semicrystalline aliphatic polycarbonates. This conversion is achieved by using enantiomerically pure, biobased (R)-(−)-1,3-butanediol (bio-BG) as a renewable feedstock. Ring-opening polymerization from select catalysts at low temperatures can yield regioregular poly((R)-1,3-butylene carbonate) ( R-PBC) with semicrystalline properties (X reg = > 0.99; T m = 72 °C). Along with the R-enantiomeric polymer, the alternate stereochemical polymers (using S- and racemic BC) were investigated. Our analysis shows that the highest level of crystallinity is achieved with regioregular, biobased R -PBC compared to the petrol-based S- and racemic congeners. This work shows the potential of stereochemically pure bio-BG as a starting material for semicrystalline, aliphatic carbonates when high regioregularity is achieved in the polymer microstructure. The synthesis and thermal characterization of regioregular butylene carbonate polymers are described in detail.

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“…4, which follows the "coordination-insertion" pathway that was reported in several previous studies for the ringopening transesterification polymerization (ROTEP) of cyclic ester catalyzed by other singlesite metal alkoxide complexes. [37][38][39][40][41][42] The best catalyst used in this study is tetraphenyltin. The calculations show that the direct insertion of the phenyl group of tetraphenyltin into the coordinated ester monomer has to cross an extremely high activation barrier (45.4 kcal/mol, supporting information (SI)).…”

Section: Resultsmentioning

confidence: 99%

Effective Regulation of Polycaprolactone Molecular Weight and Oligomers Content Using Tetraphenyltin Catalyst

Gong¹,

Li²,

et al. 2020

Preprint

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There is a lack of effective approaches that produce polycaprolactone materials (PCL) with a high molecular weight, narrow polymer dispersity index (PDI), and fewer formation of oligomers. The immigration of the remained oligomers predominantly causes poor PCL quality and induces odor release. This limits the extensive application of PCL materials. This study investigates the effects of different catalysts and loadings on the PCL performance along with the formation of oligomers in detail. The oligomers were successfully separated using gel permeation chromatography (GPC). This was followed by a quantitative and qualitative identification using high-resolution mass spectrometry (HRMS) and low field nuclear magnetic (L-field NMR) analysis. The results show that tetraphenyltin is an effective catalyst to promote the reaction and produce high-performance PCL that possesses the highest Mn (65000), narrowest PDI (1.37), and the lowest content of oligomers (7.466 wt.%). Density functional theory (DFT) studies that were combined with characterizing key intermediates verified that an anhydride bond was formed close to the end hydroxyl group in the PCL chain because of the special catalytic mechanism. This unusual chemical structure successfully inhibited the chain from being broken by the “back-biting” behavior, which is helpful for lowering the content of oligomers. This study can provide a scalable synthetic approach to creating high-performance polymers.

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Computational Prediction and Experimental Verification of ε-Caprolactone Ring-Opening Polymerization Activity by an Aluminum Complex of an Indolide/Schiff-Base Ligand

Cited by 22 publications

References 32 publications

Aluminum Complexes Bearing Bidentate Amido–Phosphine Ligands for Ring-Opening Polymerization of ε-Caprolactone: Steric Effect on Coordination Chemistry and Reactivity

Aluminum Complexes Bearing Bidentate Amido–Phosphine Ligands for Ring-Opening Polymerization of ε-Caprolactone: Steric Effect on Coordination Chemistry and Reactivity

Regioregular Polymers from Biobased (R)-1,3-Butylene Carbonate

Effective Regulation of Polycaprolactone Molecular Weight and Oligomers Content Using Tetraphenyltin Catalyst

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