Abstract
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.
Highlights
Biodegradable and biocompatible polymers have attracted the most attention of the researchers in the last two decades [1,2,3,4,5]
We summarized the results of density functional theory (DFT) modeling of coordination Ring-opening polymerization (ROP) of cyclic esters
In addition to discussion of the ROP of traditional cyclic esters, in part four we address the issue of the polymerization of cyclic ethylene phosphate monomers [12,13] (ROEP in Scheme 1) due to similarity of the reaction mechanisms for cyclic lactones, lactides, carbonates and phosphates, related compounds
Summary
Biodegradable and biocompatible polymers have attracted the most attention of the researchers in the last two decades [1,2,3,4,5]. The formation of syndiotactic polymers in ROP of allyl β-malolactonate catalyzed by yttrium complexes with η4-coordinated NOXO-type ligand with chloro substituents at benzene rings (6a, b, Figure 2b) was analyzed using DFT modeling by Carpentier et al at the BP86-RI/def-TZVP level of theory [43]. They considered two possible types of the reaction mechanism, mononuclear and binuclear, taking into account the possible involvement of Cl···O halogen bonding between ortho-halogen substituents and oxygen from carbonyl/alkoxy groups of the propagating poly(alkoxybutyrate) chain. The results and, especially, methodology of these works that includes the analysis of the chelate formation, possibility of the binuclear mechanism, and clear understanding of the difference between initiation and propagation stages, are essential for DFT modeling of polymerization of other cyclic esters
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