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The role of activator and deactivator species in the surface‐initiated atom‐transfer radical polymerization of styrene using CuBr/CuBr2/pentamethyldiethylenetriamine as a model system is described. The influence of initially added deactivator with respect to the degree of controlling the layer growth and thickness is studied. Variation of the activator concentration results in changes of the kinetics as well as brush thicknesses consistent with the well‐known rate laws of ATRP.

A detailed investigation of the atom transfer radical polymerization of methyl methacrylate (MMA) with the ethyl 2-bromoisobutyrate (2-EiBBr)/CuBr/N,N,N‘,N‘,N‘ ‘-pentamethyldiethylenetriamine (PMDETA) catalyst system in anisole was performed at 30 °C. The number-average molecular weight of the PMMA was observed to increase gradually and linearly while the polydispersity index (PDI) remained narrow throughout the reaction time. The summary of these studies showed that PMMA with molecular weight up to 105 g/mol could be synthesized in a controlled fashion at room temperature. The new route developed was utilized to demonstrate the facile synthesis of ABC and CBABC multiblock copolymers of styrene, tert-butyl acrylate (tBA), and MMA. For this, the starting blocks of AB and BAB were synthesized by coupling different ATRP methods reported. The end-block consisting of PMMA was synthesized by the ATRP of MMA using the CuCl/PMDETA catalyst system (halogen exchange) with anisole as the solvent at room temperature. Gel permeation chromatography (GPC) was used to determine the M n, M w, and PDI of the polymers synthesized. The PDI of all the block copolymers is found to be low (1.1−1.4). 1H NMR spectroscopy was used to determine the chemical composition of the block copolymers. Additional evidence for the blocky nature was also gained from FT-IR and thermal analysis.

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Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as 0.90 molecules/nm2. The organic–inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting reaction.

A rapid and efficient process for the separation of chitin from waste prawn shells using hot glycerol pretreatment is reported. The pretreatment of waste prawn shell in hot glycerol enables the removal of protein possibly through dehydration and temperature induced fragmentation into low molecular weight water-soluble fragments, which are subsequently removed from the shell matrix by dissolution in water. In contrast, in the industrial process of preparing chitin from crustacean shells, the deproteinization is carried out with hot aqueous sodium hydroxide. The novel pretreatment present here should be applicable to all crustacean shell waste, in principle. Chitin was isolated by two different methods after the pretreatment in glycerol. In one of the methods, the pretreated shells were treated directly with citric acid to remove protein and minerals (mostly as calcium citrate). In the second method, the pretreated shells were ground and rinsed with water to remove protein fragments and part of the minerals (mostly as calcium carbonate). In the subsequent step, the residual minerals were demineralized with citric acid. The later method offers the additional advantage of removing a significant quantity of minerals without dissolution in the first step and also reduces the consumption of citric acid used in the demineralization step resulting in reduction in the emission of carbon dioxide. In addition, the glycerol can be used again for three successive cycles of treatment and beyond that can be recovered with charcoal treatment (90% recovery) and used again. The present method offers distinct advantages over the chemical method, such as lower residual protein (0.24%) and higher crystallinity index (80.9%) of chitin in addition to the separation of nanofibers of chitin. The recovery of byproducts, glycerol, and the simplicity of the present method guarantee that it could be a greener alternative to the chemical method, predominant in the current industrial scale production of chitin.

The surface-initiated ATRP of benzyl methacrylate, methyl methacrylate, and styrene from magnetite nanoparticle is investigated, without the use of sacrificial (free) initiator in solution. It is observed that the grafting density obtained is related to the polymerization kinetics, being higher for faster polymerizing monomer. The grafting density was found to be nearly 2 chains/nm2for the rapidly polymerizing benzyl methacrylate. In contrast, for the less rapidly polymerizing styrene, the grafting density was found to be nearly 0.7 chain/nm2. It is hypothesized that this could be due to the relative rates of surface-initiated polymerization versus conformational mobility of polymer chains anchored by one end to the surface. An amphiphilic diblock polymer based on 2-hydroxylethyl methacrylate is synthesized from the polystyrene monolayer. The homopolymer and block copolymer grafted MNs form stable dispersions in various solvents. In order to evaluate molecular weight of the polymer that was grafted on to the surface of the nanoparticles, it was degrafted suitably and subjected to gel permeation chromatography analysis. Thermogravimetric analysis, transmission electron microscopy, and Fourier transform infrared spectroscopy were used to confirm the grafting reaction.