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

Two 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 1 H and 13 C 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 1 H 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 1 H 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.