scholarly journals Mechanistic Insights of BHT-Mg-Catalyzed Ethylene Phosphate’s Coordination Ring-Opening Polymerization: DFT Modeling and Experimental Data

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1105 ◽  
Author(s):  
Ilya Nifant’ev ◽  
Andrey Shlyakhtin ◽  
Maxim Kosarev ◽  
Stanislav Karchevsky ◽  
Pavel Ivchenko
Keyword(s):  
Ring Opening ◽  
Activation Barrier ◽  
Ring Opening Polymerization ◽  
High Rate ◽  
Basis Set ◽  
Cyclic Esters ◽  
Dft Modeling ◽  
Binuclear Species ◽  
Poly Ethylene ◽  
First Time

Poly(ethylene phosphates) are promising polymers for use in biomedical applications. Catalytic ring-opening polymerization (ROP) of cyclic ethylene phosphate monomers (CEPMs) is the most effective approach for obtaining these polymers. The mechanism of coordination ROP of CEPMs remains unclear. We report, for the first time, the results of DFT modeling of CEPM ROP. In these calculations by Gaussian-09 program package with the B3PW91/DGTZVP basis set, we explored methyl ethylene phosphate (MeOEP) ROP catalyzed by dimeric and monomeric catalytic species derived from heteroleptic complex [(BHT)Mg(μ-OBn)(THF)]2 (Mg1, BHT = 2,6-di-tert-butyl-4-methylphenolate). Analysis of the reaction profiles for the binuclear and mononuclear reaction mechanisms allowed us to conclude that the ROP of MeOEP is preferentially catalyzed by mononuclear Mg complexes. This estimation was confirmed by comparative polymerization experiments using MeOEP and traditional monomers ε-caprolactone (εCL), racemic lactide (rac-LA), and l-lactide (l-LA) initiated by Mg1. ROP of MeOEP proceeds at an extremely high rate due to the substantially lower activation barrier calculated for mononuclear mechanism in comparison with that of cyclic esters that polymerize without the dissociation of BHT-Mg binuclear species. We also demonstrated the use of MeOEP as a "monomerization" agent in the synthesis of MeOEP-lactide block copolymers. Comparison of the multiple acceleration of l-LA ROP after MeOEP prepolymerization and formation of atactic PLA blocks in rac-LA polymerization with the heterotactic PLA formation during Mg1-catalyzed homopolymerization also confirmed the mononuclear nature of the polyphosphate-containing catalytic particles.

scholarly journals DFT Visualization and Experimental Evidence of BHT-Mg-Catalyzed Copolymerization of Lactides, Lactones and Ethylene Phosphates

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1641 ◽  
Author(s):  
Ilya Nifant’ev ◽  
Andrey Shlyakhtin ◽  
Maxim Kosarev ◽  
Dmitry Gavrilov ◽  
Stanislav Karchevsky ◽  
...  
Keyword(s):  
Ring Opening ◽  
Density Functional ◽  
Point Of View ◽  
Basis Set ◽  
Random Copolymers ◽  
Key Factors ◽  
Functional Theory ◽  
Cyclic Esters ◽  
Dft Modeling ◽  
Derivatives Of

Catalytic ring-opening polymerization (ROP) of cyclic esters (lactides, lactones) and cyclic ethylene phosphates is an effective way to process materials with regulated hydrophilicity and controlled biodegradability. Random copolymers of cyclic monomers of different chemical nature are highly attractive due to their high variability of characteristics. Aryloxy-alkoxy complexes of non-toxic metals such as derivatives of 2,6-di-tert-butyl-4-methylphenoxy magnesium (BHT-Mg) complexes are effective coordination catalysts for homopolymerization of all types of traditional ROP monomers. In the present paper, we report the results of density functional theory (DFT) modeling of BHT-Mg-catalyzed copolymerization for lactone/lactide, lactone/ethylene phosphate and lactide/ethylene phosphate mixtures. ε-Caprolactone (ε-CL), l-lactide (l-LA) and methyl ethylene phosphate (MeOEP) were used as examples of monomers in DFT simulations by the Gaussian-09 program package with the B3PW91/DGTZVP basis set. Both binuclear and mononuclear reaction mechanistic concepts have been applied for the calculations of the reaction profiles. The results of calculations predict the possibility of the formation of random copolymers based on l-LA/MeOEP, and substantial hindrance of copolymerization for ε-CL/l-LA and ε-CL/MeOEP pairs. From the mechanistic point of view, the formation of highly stable five-membered chelate by the products of l-LA ring-opening and high donor properties of phosphates are the key factors that rule the reactions. The results of DFT modeling have been confirmed by copolymerization experiments.

scholarly journals DFT Modeling of Organocatalytic Ring-Opening Polymerization of Cyclic Esters: A Crucial Role of Proton Exchange and Hydrogen Bonding

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2078 ◽  
Author(s):  
Ilya Nifant’ev ◽  
Pavel Ivchenko
Keyword(s):  
Ring Opening ◽  
Density Functional ◽  
Comparative Modeling ◽  
Ring Opening Polymerization ◽  
Proton Exchange ◽  
Dft Methods ◽  
Experimental Proof ◽  
Cyclic Esters ◽  
Dft Modeling

Organocatalysis is highly efficient in the ring-opening polymerization (ROP) of cyclic esters. A variety of initiators broaden the areas of organocatalysis in polymerization of different monomers, such as lactones, cyclic carbonates, lactides or gycolides, ethylene phosphates and phosphonates, and others. The mechanisms of organocatalytic ROP are at least as diverse as the mechanisms of coordination ROP; the study of these mechanisms is critical in ensuring the polymer compositions and architectures. The use of density functional theory (DFT) methods for comparative modeling and visualization of organocatalytic ROP pathways, in line with experimental proof of the structures of the reaction intermediates, make it possible to establish these mechanisms. In the present review, which continues and complements our recent manuscript that focused on DFT modeling of coordination ROP, we summarized the results of DFT modeling of organocatalytic ROP of cyclic esters and some related organocatalytic processes, such as polyester transesterification.

scholarly journals Coordination Ring-Opening Polymerization of Cyclic Esters: A Critical Overview of DFT Modeling and Visualization of the Reaction Mechanisms

Molecules ◽  
2019 ◽  
Vol 24 (22) ◽  
pp. 4117 ◽  
Author(s):  
Ilya Nifant’ev ◽  
Pavel Ivchenko
Keyword(s):  
Ring Opening ◽  
Density Functional ◽  
Transition States ◽  
Ring Opening Polymerization ◽  
Molecular Structures ◽  
Data Sets ◽  
Dft Methods ◽  
Cyclic Esters ◽  
Dft Modeling ◽  
The Difference

Ring-opening polymerization (ROP) of cyclic esters (lactones, lactides, cyclic carbonates and phosphates) is an effective tool to synthesize biocompatible and biodegradable polymers. Metal complexes effectively catalyze ROP, a remarkable diversity of the ROP mechanisms prompted the use of density functional theory (DFT) methods for simulation and visualization of the ROP pathways. Optimization of the molecular structures of the key reaction intermediates and transition states has allowed to explain the values of catalytic activities and stereocontrol events. DFT computation data sets might be viewed as a sound basis for the design of novel ROP catalysts and cyclic substrates, for the creation of new types of homo- and copolymers with promising properties. In this review, we summarized the results of DFT modeling of coordination ROP of cyclic esters. The importance to understand the difference between initiation and propagation stages, to consider the possibility of polymer–catalyst coordination, to figure out the key transition states, and other aspects of DFT simulation and visualization of ROP have been also discussed in our review.

A switchable dimeric yttrium complex and its three catalytic states in ring opening polymerization

2021 ◽  
Author(s):  
Shijie Deng ◽  
Paula L. Diaconescu
Keyword(s):  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Oxidation States ◽  
Cyclic Esters

A dimeric yttrium phenoxide complex can be oxidized in a stepwise fashion to access three oxidation states. The three states show different activity in the ring opening polymerization of cyclic esters and epoxides.

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