Characterization of molecular association of poly(2-oxazoline)s-based micelles with various epoxides and diols via the Flory–Huggins theory: a molecular dynamics simulation approach

Abstract

The hydrolytic kinetic resolution (HKR) of epoxides has been performed in a shell-crosslinked micellar (SCM) nanoreactor consisting of amphiphilic triblock copolymers based on poly(2-oxazline)s polymer derivatives with attached Co(III)-salens to the micelle core. To investigate the effect of the molecular interaction of reactant/product molecules with the SCM nanoreactor on the rate of HKR, we calculated the Flory–Huggins interaction parameters (χ) using the molecular dynamics simulation method. For this, the blend systems were constructed with various compositions such as 15, 45, and 70 wt% of the reactant/product molecules with respect to the polymers such as poly(2-methyl-2-oxazoline) (PMOX), poly(2-(3-butinyl)2-oxazoline) (PBOX), and poly(methyl-3-oxazol-2-yl)pentanoate with Co(III)-salen (PSCoX). From the χ parameters, we demonstrate that the miscibility of reactants/products with polymers has a strong correlation with the experimental reaction rate of the HKR: phenyl glycidyl ether (Reac-OPh) > epoxyhexane (Reac-C4) > styrene oxide (Reac-Ph) > epichlorohydrin (Reac-Cl). To validate this finding, we also conducted the potential of mean force analysis using steered molecular dynamics simulation for the molecular displacement of Reac-Cl and Reac-OPh through PMOX and PSCoX, revealing that the free energy reduction was greater when Reac-OPh molecule enters the polymer phase compared to Reac-Cl, which agrees with the findings from the χ parameters calculations.