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

Abstract

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.

Growth responses and yield of cauliflower (Brassica oleracea var. botrytis L.) to the delayed transplanting and drought stress

“…Younger seedlings could adapt to new environment faster than older seedlings promoting better growth and higher yield. The phyllochronic utilization followed by younger aged seedlings improve plant growth parameters [14]. Younger seedlings containing higher nitrogen and higher ability to faster resumption of phyllochron development rate [15].…”

“…Water deficit during juvenility and curd induction reduced cauliflower's growth and marketable yield [11]. However, drought-resistant plants can regulate biophysico-chemical events to tolerate water deficit stress [13,14]. Therefore, this study was conducted to evaluate the growth responds of cauliflower to the delay of transplanting and drought stress condition.…”

Description of Chiral Complexes within Functional-Group Symmetry-Adapted Perturbation Theory—The Case of (S/R)-Carvone with Derivatives of (−)-Menthol

“… 10 , 17 , 18 For instance, it was employed as an initiator in an atom transfer radical polymerization of styrene. 19 Similarly, carvone can also serve as a substrate for polymer chemistry. 18 , 20 ( R )-Carvone has recently been used to obtain new chiral isoxazoles and pyrazoles having a monoterpenic skeleton, which were further tested for cytotoxicity against human HT-1080, MCF-7, and A-549 cancer cells.…”

“…Both serve as popular model molecules of active, natural products, for instance, in studies of interactions with bioreceptors, , in the formation of conjugates with nanoparticles, in drug-delivery systems, or in odor sensing . Being cheap, abundant, and easily available, menthol is widely used in synthetic chemistry, in particular, in asymmetric synthesisfor extensive reviews, see, for example, refs. ,, For instance, it was employed as an initiator in an atom transfer radical polymerization of styrene . Similarly, carvone can also serve as a substrate for polymer chemistry. , ( R )-Carvone has recently been used to obtain new chiral isoxazoles and pyrazoles having a monoterpenic skeleton, which were further tested for cytotoxicity against human HT-1080, MCF-7, and A-549 cancer cells .…”