L‐menthol‐based initiators for atom transfer radical polymerization of styrene

Abstract

ABSTRACTTwo new atom transfer radical polymerization (ATRP) initiators, 2‐isopropyl‐5‐methylcyclohexyl 2‐bromopropanoate (1) and 2‐Isopropyl‐5‐methylcyclohexyl 2‐bromo‐2‐methylpropanoate (2), have been synthesized by the reaction of 2‐bromopropanoyl bromide and 2‐bromo‐2‐methylpropanoyl bromide, respectively, with L‐menthol and characterized by 1H and 13C NMR and FTIR spectroscopic studies. ATRP of styrene has successfully been carried out in a control manner using these initiators along with catalyst/ligand system consisting of Cu(I)Br/N,N,N /,N /,N //‐pentamethyldiethylenetriamine. Polymerizations have yielded polystyrenes (PSts) of controlled molecular weight with low polydispersity index having a menthyl end group, as confirmed by 1H NMR and gel permeation chromatography [GPC]. The controlled nature of the polymerization has also been confirmed by kinetic study of the polymerization process monitored via 1H NMR and GPC. Initiator 2 has evolved as most efficient among the two. The obtained end‐functional PSt has also been used as a macroinitiator for homochain extension with styrene and heterochain extension with methyl methacrylate to produce PSt‐b‐PMMA, showing the living nature of the polymerization process. In comparison with the PSt sample prepared using widely used initiator ethyl‐2‐bromo‐isobutyrate with almost the same molecular weight and polydispersity, initiator 2‐made L‐menthyl‐capped PSt has shown higher light transmission properties of its dichloromethane solution at ~259 nm, higher thermal stability, lower glass transition temperature, a broad melting temperature, and higher surface roughness over its film. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47964.