Tailor-Made Stereoblock Copolymers of Poly(lactic acid) by a Truly Living Polymerization Catalyst

Rosen, Tomer; Goldberg, Israel; Venditto, Vincenzo; Kol, Moshe

doi:10.1021/jacs.6b07287

Cited by 75 publications

(69 citation statements)

References 33 publications

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“…It is of great interest for various biomedical as well as ecological applications, including drug-delivery systems and tissue engineering [1][2][3][4][5][6][7][8]. PLA has attracted much attention from researchers in both industry and academia.…”

Section: Introductionmentioning

confidence: 99%

Computational Studies on the Selective Polymerization of Lactide Catalyzed by Bifunctional Yttrium NHC Catalyst

et al. 2017

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Abstract:A theoretical investigation of the ring-opening polymerization (ROP) mechanism of rac-lactide (LA) with an yttrium complex featuring a N-heterocyclic carbine (NHC) tethered moiety is reported. It was found that the carbonyl of lactide is attacked by N(SiMe 3 ) 2 group rather than NHC species at the chain initiation step. The polymerization selectivity was further investigated via two consecutive insertions of lactide monomer molecules. The insertion of the second monomer in different assembly modes indicated that the steric interactions between the last enchained monomer unit and the incoming monomer together with the repulsion between the incoming monomer and the ligand framework are the primary factors determining the stereoselectivity. The interaction energy between the monomer and the metal center could also play an important role in the stereocontrol.

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Section: Introductionmentioning

confidence: 99%

Computational Studies on the Selective Polymerization of Lactide Catalyzed by Bifunctional Yttrium NHC Catalyst

et al. 2017

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“…[1][2][3][4][5] Ring-opening polymerization (ROP) of cyclic ester monomers is a versatile synthetic method for generating the well-defined aliphatic polyesters. Various enzymatic, [6][7][8] metal-based catalysts, [9][10][11][12][13][14][15] and organocatalysts [16][17][18] have been developed for the ROP reactions of cyclic esters. Organocatalytic ROPs of cyclic esters have proven to be especially useful for the production of functional biodegradable polymer materials.…”

mentioning

confidence: 99%

Solvent‐free ring‐opening polymerization of lactones with hydrogen‐bonding bisurea catalyst

Zheng

Yuan

et al. 2018

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

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Development of effective organocatalysts for the living ring‐opening polymerization (ROP) of lactones is highly desired for the preparation of biocompatible and biodegradable polyesters with controlled microstructures and physical properties. Herein, a new class of hydrogen‐bond donating bisurea catalysts is reported for the ROP of lactones under solvent‐free conditions. ROP of lactones mediated by the bisurea/7‐methyl‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (MTBD) catalyst exhibits a living/controlled manner, affording the polymers and copolymers with the well‐defined structure, predictable molecular weight, narrow molecular weight distribution, and high selectivity for monomer at low catalyst loadings at ambient temperature. The possible mechanism of bisurea/MTBD‐catalyzed ROP of lactones is proposed, in which the bisurea activates the carbonyl group of lactones while MTBD facilitates the nucleophilic attack of the initiating/propagating alcohol by hydrogen bonding. Moreover, the poly(ε‐caprolactone‐co‐δ‐valerolactone) [P(CL‐co‐VL)] random copolymers with various compositions were synthesized using the bisurea/MTBD catalyst. The measurements of thermal properties and crystalline structure demonstrate that the CL and VL units are cocrystallized in the crystalline phase of P(CL‐co‐VL) copolymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 90–100

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“…The coordination‐insertion and the activated monomer were two main mechanisms for the ROP of cyclic esters . To explore the initiation and polymerization mechanism for complexes 1 – 3 , the interactions between monomer, Mg complexes and ROH ( i PrOH or BnOH) were investigated by in situ NMR at ambient temperature, respectively.…”

Section: Resultsmentioning

confidence: 99%

Homoleptic, bis‐ligated magnesium complexes for ring‐opening polymerization of lactide and lactones: Synthesis, structure, polymerization behavior and mechanism studies

Chen

Wang

Pan

et al. 2019

Applied Organom Chemis

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Bis‐ligated, homoleptic magnesium complexes 1–3 were synthesized through the reaction of 1 equiv. dibutyl magnesium with 2 equiv. β‐ketiminato ligands bearing different substituents on the nitrogen atom and 8 position on benzocyclohexanone. All of the complexes were identified by nuclear magnetic resonance (NMR) and X‐ray crystallography. Complexes 2 and 3 adopted distorted tetrahedral geometry around Mg, by chelating of two ancillary ligands, while complex 1 adopted a dimeric structure with penta‐coordination around Mg. These complexes can be used as efficient catalysts for the ring‐opening polymerization of L‐lactide, ε‐caprolactone, δ‐valerolactone (δ‐VL) and trimethylene carbonate in the presence of alcohol as a co‐initiator. With the increasing steric bulk of the ancillary ligands, the catalytic activity of Mg complexes was improved significantly. Particularly, complex 3 having the largest steric hindrance showed excellent catalytic performance for the polymerization of δ‐VL. It could polymerize 800 equiv. δ‐VL in 10 min, and produce polyvalerolactone with narrow molecular weight distributions (Mw/Mn < 1.2) at 35°C or higher temperature. No transesterification side reaction was observed. Moreover, complex 3 exhibited good tolerance to excessive alcohol and an immortal polymerization characteristic. The mechanism studies by in situ NMR demonstrated a coordination‐insertion process. Besides, it revealed that the steric bulky substituents in the active species derived from the complex and alcohol prevented the metal center from deactivation.

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Tailor-Made Stereoblock Copolymers of Poly(lactic acid) by a Truly Living Polymerization Catalyst

Cited by 75 publications

References 33 publications

Computational Studies on the Selective Polymerization of Lactide Catalyzed by Bifunctional Yttrium NHC Catalyst

Computational Studies on the Selective Polymerization of Lactide Catalyzed by Bifunctional Yttrium NHC Catalyst

Solvent‐free ring‐opening polymerization of lactones with hydrogen‐bonding bisurea catalyst

Homoleptic, bis‐ligated magnesium complexes for ring‐opening polymerization of lactide and lactones: Synthesis, structure, polymerization behavior and mechanism studies

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