Computational Investigation of Mechanisms for Ring-Opening Polymerization of ε-Caprolactone:  Evidence for Bifunctional Catalysis by Alcohols

Abstract

Stepwise addition/elimination and concerted mechanisms for the methanolysis of ε-caprolactone, as a model for the initiation and propagation of ring-opening polymerization (ROP), have been investigated computationally using the B3LYP/6-31G* density functional method, with assistance from one or two ancillary methanol molecules. The effects of specific solvation by these extra methanols in cyclic hydrogen-bonded clusters are very significant, with barrier height reductions of about 50 kJ mol(-)(1). However, the effects of bulk solvation as treated by the polarized continuum model are almost negligible. Increasing the ring size lowers the barriers for both the addition and elimination steps of the stepwise mechanism but does not do so for the concerted mechanism; a stepwise mechanism is preferred for methanol-assisted ROP. The essential catalytic role of solvent molecules in this reaction is to avoid the unfavorable accumulation or separation of charges.

Zn(II) and Cu(II) unsymmetrical formamidine complexes as effective initiators for ring‐opening polymerization of cyclic esters

“…Zn(II) complexes showed superior activity over the Cu(II) analogues. Induction periods of about 6 h were observed for Zn(II) complexes while for Cu(II) complexes they range from 10 – 20 h. There are three main possible explanations for difference in induction time, namely catalyst conformational changes to form the transition state, thermal effects and catalyst dissociation to less active catalytic species . There was no further attempt to investigation the type of induction time in our system.…”

From Zn(C6F5)2 to ZnEt2‐based Lewis Pairs: Significantly Improved Catalytic Activity and Monomer Adaptability for the Ring‐opening Polymerization of Lactones

“…The simple structure of ZnEt 2 /DMAP Lewis pair gives us an opportunity to gain insights into the reaction mechanism of this unique catalytic system by DFT calculations. All calculations were performed at the B3LYP level of theory, which has been widely used in the investigation of the ROP mechanism . Two possible reaction mechanisms involving single molecular initiation and biomolecular initiation were proposed in scheme .…”

A DFT Study of the Mechanism of Polymerization of ε‐Caprolactone Initiated by Organolanthanide Borohydride Complexes

“…[18] Europium was treated with a Stuttgart-Dresden pseudopotential that includes the 4f electrons in core, in combination with their adapted basis set. [20] In all cases, the basis set was augmented by a set of f-polarization functions.…”