Cation−π Interactions Accelerate the Living Cationic Ring-Opening Polymerization of Unsaturated 2-Alkyl-2-oxazolines

• DOI: 10.1021/acs.macromol.0c00865
• Publication Date: 2020-05-04T13:26:20Z
• Authors: Elias Van Den Broeck; Bart Verbraeken; Karen Dedecker; Pieter Cnudde; Louis Vanduyfhuys; Toon Verstraelen; Kristof Van Hecke; Valentin Victor J...; Saron Catak; Richard Hoogenboom; Veronique Van Spe...
• Keywords: Cationic polymerization; Degree of unsaturation; Side chain; Oxazoline

Cation–dipole interactions were previously shown to have a rate-enhancing effect on the cationic ring-opening polymerization (CROP) of 2-oxazolines bearing side-chain ester functionality. In line with this, similar rate enhancement—via intermolecular cation−π interactions—was anticipated occur when π-bonds are introduced into 2-oxazoline side-chains. Moreover, incorporation allows for facile postfunctionalization resulting poly(2-oxazoline)s double and triple bonds in side-chains via various click reactions. Herein, combined molecular modeling experimental approach was used study CROP reaction rates having varying degrees unsaturation length. The presence influence degree initially confirmed by means regular dynamics simulations pentameric systems. Furthermore, combination enhanced simulations, static calculations, thorough analysis noncovalent performed unravel what extent alter kinetics. Additionally, observed trends also acetonitrile as solvent, which experimentally is performed. Most intriguingly, we found only limited intrinsic kinetics preorganization reactive complex region. latter established unsaturated center through interplay between cation−π, π–π, π–induced dipole, cation–dipole interactions. These findings led us propose two-step mechanism comprised an equilibration step step. unsaturation, effect, determined following trend rates: n-ButylOx < ButenOx ButynOx ≥ PentynOx. determining constants.