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Cellulose nanocrystals (CNCs) were converted into a CO2-responsive composite nanomaterial by grafting poly(dimethylaminoethyl methacrylate) (PDMAEMA), poly(diethylaminoethyl methacrylate) (PDEAEMA), and poly(diisopropylaminoethyl methacrylate) (PDPAEMA) onto its surface using both grafting-to and grafting-from approaches. The zeta potential (ζ) of the graft-modified CNC could be reversibly switched by protonation/deprotonation of the tertiary amine groups simply by sparging with CO2 and N2, respectively. Depending on the grafting density and the molecular weight of the polymer grafts, CNC can form stable aqueous dispersions at either mildly acidic pH (under CO2) or mildly basic (under N2) conditions. Moreover, it was also determined that the CNC hydrophobicity, assessed using phase-shuttling experiments at different pH values, was also dependent on both the grafting density and molecular weight of the polymer grafts, thereby making it possible to easily tune CNC dispersibility and/or hydrophobicity.

Starch nanoparticles (SNP) were modified with synthetic polymers using the “grafting to” approach and nitroxide-mediated polymerization. SG1-capped poly(methyl methacrylate-co-styrene) (P(MMA-co-S)...

Cold water-soluble starch (CWS) is a polysaccharide that is industrially important for several applications including paper coatings, but the high viscosity of starch solutions limits the amount of starch that can be incorporated in many applications. Due to the poor mechanical properties of starch and poor dispersibility of starch in hydrophobic matrices, it is often chemically modified to make it more useful. Herein, we report the first grafting from (co)polymerisation of CWS via nitroxide-mediated polymerisation (NMP) of methyl methacrylate-co-styrene, methyl acrylate, and acrylic acid. Our three step approach consists of: (1) modification of CWS with 4-vinylbenzyl chloride; (2) functionalisation with 2-methyl-2-[N-tertbutyl-N-(diethoxy-phosphoryl-2,2-dimethylpropyl)-aminoxy] propionic acid initiator; and (3) grafting from (co)polymerisation via NMP. The (co)polymerisations were well controlled showing linear reaction kinetics for all monomers and relatively low dispersities (

Lead bromide-based halide perovskites are of interest for wide-band-gap (>1.75 eV) absorbers for low-cost solar spectrum splitting to boost solar-to-electrical energy conversion efficiency/area by ...

Interest in the development of new hybrid materials based on natural polysaccharides has grown exponentially in the last decade. Such materials are commonly obtained by the graft modification of polysaccharides via reversible deactivation radical polymerization (RDRP). Research has focused on the use of RDRP techniques, including ATRP (atom transfer radical polymerization), NMP (nitroxide-mediated polymerization) and RAFT (reversible addition–fragmentation chain transfer polymerization), not only because of the good control over the molecular weight distribution that RDRP provides, but also because of the complex macromolecular architectures that can be achieved. This review highlights the most recent development, challenges, uses and applications of the polymer graft modification of several common natural polysaccharides (chitin, chitosan, alginate, dextran, starch and cellulose derivatives) via RDRP.

Cellulose nanocrystals (CNC) are a renewable resource possessing extraordinary physical, mechanical, and optical properties. CNC are readily dispersible only under hydrophilic environments, such as aqueous media and very polar solvents. Different approaches have been attempted to alter the surface properties and thereby improve CNC dispersibility in organic solvents and polymers (hydrophobic media), including functionalisation with small molecules and grafting of polymer chains to the CNC surface. However, when hydrophobic polymer chains are grafted on the CNC surface, the CNC are irreversibly altered toward increased hydrophobicity, which can be undesirable for some applications. Grafting stimuli-responsive polymer chains to the CNC surface offers a solution to this problem. We have synthesized stimuli-responsive CNC whose surface properties can be reversibly switched using only carbon dioxide (CO2) as the trigger to conduct the switching process. The surfaces were modified using surface-initiated nitroxide mediated polymerisation (SI-NMP) with CO2-responsive polymers poly(dimethylaminoethyl methacrylate) (PDMAEMA), poly(diethylaminoethyl methacrylate) (PDEAEMA) and poly(dimethylaminopropyl methacrylamide) (PDMAPMAm).

Starch nanoparticles (SNP) are attracting increased attention as a renewable bio-based alternative to petroleum-based polymers in the materials community. In this work, we describe the grafting from of SNP with synthetic polymers via nitroxide-mediated polymerization (NMP). Varying amounts of poly(methyl methacrylate-co-styrene) (P(MMA-co-S)), poly(methyl acrylate) (PMA) and poly(acrylic acid) (PAA) were grafted from the surface of SNP in a three-step process. The grafting of synthetic polymers from the surface of SNP was confirmed by FTIR, 1H NMR, elemental analysis and thermogravimetric analysis. These new tailor-made starch-based hybrid materials could find use in paper coatings, adhesives, paints, as well as in polymer latex applications.

Replacing petro-based materials with renewably sourced ones has clearly been applied to polymers, such as those derived from itaconic acid (IA) and its derivatives. Di-n-butyl itaconate (DBI) was (co)polymerized via nitroxide mediated polymerization (NMP) to impart elastomeric (rubber) properties. Homopolymerization of DBI by NMP was not possible, due to a stable adduct being formed. However, DBI/styrene (S) copolymerization by NMP at various initial molar feed compositions fDBI,0 was polymerizable at different reaction temperatures (70&ndash, 110 &deg, C) in 1,4 dioxane solution. DBI/S copolymerizations largely obeyed first order kinetics for initial DBI compositions of 10% to 80%. Number-average molecular weight (Mn) versus conversion for various DBI/S copolymerizations however showed significant deviations from the theoretical Mn as a result of chain transfer reactions (that are more likely to occur at high temperatures) and/or the poor reactivity of DBI via an NMP mechanism. In order to suppress possible intramolecular chain transfer reactions, the copolymerization was performed at 70 &deg, C and for a longer time (72 h) with fDBI,0 = 50%&ndash, 80%, and some slight improvements regarding the dispersity (&ETH, = 1.3&ndash, 1.5), chain activity and conversion (~50%) were observed for the less DBI-rich compositions. The statistical copolymers produced showed a depression in Tg relative to poly(styrene) homopolymer, indicating the effect of DBI incorporation.

In this study, we report the use of a double-headed dialkoxyamine trithiocarbonate (I) capable of acting as chain transfer agent via reversible addition-fragmentation chain transfer polymerization or as initiator via nitroxide-mediated polymerization. It is worth mentioning that I was revealed as an effective dual chain transfer agent in the synthesis of multiblock copolymers via bulk and emulsion processes. In this article, we report the employing of I in dispersed systems to obtain amphiphilic multiblock copolymers and latexes. In this case, a water soluble macroagent of PAA previously synthetized was used in disperse media using a mixture of methanol/water (70:30, w/w). Stable latexes were obtained via polymerization-induced self-assembly and surface-initiated polymerization of SSNa from alkoxyamine-functionalized latex PAA-b-PS-b-PAA was also obtained © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 437–444

The grafting of well-defined polystyrene to graphene oxide (GO) using nitroxide-mediated polymerization (NMP) is demonstrated by a two-step reaction. In the first step, GO is functionalized with glycidyl methacrylate (GMA) to yield GO-GMA. Polystyrene (PS), previously synthesized via SG1-based NMP, is then grafted to GO-GMA by a simple reaction between the SG1 end group and the GMA double bond to yield GO-GMA-g-PS. 1H, heteronuclear single-quantum correlation (HSQC), nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), Raman, Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and thermogravimetric analysis (TGA) are consistent with attachment of the GMA group to the GO surface and with polystyrene being grafted to the GO surface to form the GO-GMA-g-PS nanocomposite (NC). GPC analysis shows a number-average molecular weight of 3330 g mol−1 for the PS with molecular weight dispersity (Ð) of 1.13. Up to 28 mass% of PS has been introduced into the GO NC. The present “grafting-to” methodology holds promise for the facile and clean synthesis of graphene oxide polymer NCs.

Cellulose nanocrystals (CNC) have become the subject of increasing research interest because of their unique physical, chemical and mechanical properties, including being a renewable material. While CNC shows promise as a reinforcing material in polymer-based composites, the hydrophilic surface of CNC makes dispersibility in most hydrophobic polymers very difficult which limits potential applications. In this study, we report the first graft modification of CNC using nitroxide-mediated radical polymerisation. The CNC surface was first functionalised with the nitroxide SG1 (4-(diethoxyphosphinyl)-2,2,5,5-tetramethyl-3-azahexane-N-oxyl), yielding a CNC-macroalkoxyamine. Poly(methyl acrylate) and poly(methyl methacrylate) chains were then grafted from the CNC-macroalkoxyamine surface to yield polymer graft modified CNC.

The PEGlytation of CTS with poly(poly(ethyleneglycol) methyl ether methacrylate-co-styrene), poly(PEGMA-co-S), via nitroxide-mediated polymerization (NMP) using both grafting to and from approaches has been performed. To conduct the PEGylation of CTS via grafting to, CTS was first functionalized with glycidyl methacrylate (GMA) yielding CTS-g-GMA macromer. Poly(PEGMA-co-S), synthesized via NMP, was then grafted to the CTS-g-GMA. For PEGylation via grafting from, CTS-g-GMA was first converted into a macroalkoxyamine using an SG1-based alkoxyamine. Graft copolymerization of PEGMA-co-S was then performed. The syntheses of CTS-g-GMA-poly(PEGMA-co-S) were confirmed by 1H NMR and TGA.

A novel and facile strategy to modify chitosan (CTS) with a wide catalog of well-defined molecular weight graft hydrophilic and hydrophobic polymers and copolymers via nitroxide-mediated polymerization (NMP) in homogeneous media is reported. This strategy involves three steps: functionalization of CTS with glycidyl methacrylate (GMA) and sodium dodecylbenzenesulfonate (SDBS) to yield CTS-SDBS- g -GMA, which is soluble in organic media; synthesis of SG1-terminated polymers including poly(styrene) (PS), poly(butyl acrylate) (PBA), poly(acrylic acid) (PAA), poly(styrene-b-acrylic acid) (PS- b -PAA), and poly(styrene-r-acrylic acid) (PS-r-PAA) via SG1-based nitroxide-mediated polymerization; and grafting of the SG1-functionalized polymers or copolymers to CTS-SDBS- g -GMA. Following polymerization, the SDBS was removed from the new CTS-based materials. NMR, TGA, and FT-IR were used to confirm the synthesis of CTS-SDBS-g-GMA, CTS-SDBS- g -GMA-PS, CTS-SDBS -g -GMA-PBA, CTS-SDBS- g -GMA-PAA, CTS-SDBS- g -GMA-PS- b -PAA, and CTS-SDBS- g -GMA-PS- r -PAA. The SDBS was then fully removed from the new CTS-based graft copolymers. New CTS-based materials could find potential applications in fields such as biomedical, water and wastewater treatment, biopharmaceutics and agriculture.

Chitosan was chemically functionalized with poly(diethylaminoethyl methacrylate) (PDEAEMA) using a grafting to approach to produce a CO2-responsive material for adsorbing metals from wastewater streams. A need for improved economical and greener approaches to recover heavy metals from wastewater streams exists due to increasing resource scarcity. Chitosan is currently used as an adsorbent for heavy metals but suffers from some properties that can be disadvantageous to its effectiveness; it is difficult to effectively disperse in water (which limits available surface area) and to regenerate. We set out to improve its effectiveness by grafting CO2-responsive tertiary amine containing polymers onto the chitosan backbone, with the goals of preparing and assessing a new type of adsorbent based on a novel concept; using carbon dioxide switchable polymers to enhance the performance of chitosan. PDEAEMA chains prepared by nitroxide-mediated polymerization were grafted onto chitosan functionalized with glycidyl methacrylate. In carbonated water, the grafted chitosan displayed improved dispersibility and exhibited a Ni(II) adsorption capacity higher than several other chemically functionalized chitosan variants reported in the literature with the regenerated material having a higher capacity than all physical and chemical derivatives reported in the literature. The results of this study validate the continued development of this material for applications in heavy metal removal and recovery from wastewater streams.

Chitosan-based films exhibit good oxygen barrier that degrades when exposed to high humidity. In an effort to overcome this drawback, a multilayer nanocoating consisting of crosslinkable chitosan (CHQ) and poly(acrylic acid) [PAA] is deposited on polyethylene terephthalate (PET) using layer-by-layer assembly. Chitosan is functionalized with glycidyl methacrylate to introduce acrylic functionalities within the film. The deposited films are crosslinked using a free radical initiator and this crosslinking is confirmed by FTIR and reduced film thickness. A 10-bilayer (BL) crosslinked CHQ/PAA film, which is only 165 nm thick, results in a 36× reduction of the oxygen transmission rate of PET at 90% relative humidity. To achieve these same results without crosslinking, a 15-BL unmodified chitosan (CH)/PAA film, which is almost 5× thicker, must be deposited on PET. This environmentally friendly, transparent nanocoating is promising for food packaging or protection of flexible electronics, especially in high-humidity environments.

Nitroxide-mediated polymerization (NMP) is employed to graft synthetic polymers from polysaccharides. This work demonstrates the first successful polymer grafting from starch nanoparticles (SNPs) via NMP. To graft synthetic polymers from the SNPs' surface, the SNPs are first functionalized with 4-vinylbenzyl chloride prior to reaction with BlocBuilder MA yielding a macroinitiator. Methyl methacrylate with styrene, acrylic acid, or methyl acrylate are then grafted from the SNPs. The polymerizations exhibited linear reaction kinetics, indicating that they are well controlled. Thermal gravimetric analysis and spectroscopic techniques confirmed the synthesis of the precursors materials and the success of the grafting from polymerizations. The incorporation of hydrophobic synthetic polymers on hydrophilic SNPs yields new hybrid materials that could find use in several industrial applications including paper coatings, adhesives, and paints.

As the demand for textile products and synthetic dyes increases with the growing global population, textile dye wastewater is becoming one of the most significant water pollution contributors. Azo dyes represent 70% of dyes used worldwide, and are hence a significant contributor to textile waste. In this work, the removal of a reactive azo dye (Reactive Orange 16) from water by adsorption with chitosan grafted poly(poly(ethylene glycol) methyl ether methacrylate) (CTS-GMA-g-PPEGMA) was investigated. The chitosan (CTS) was first functionalized with glycidyl methacrylate and then grafted with poly(poly(ethylene glycol) methyl ether methacrylate) using a nitroxide-mediated polymerization grafting to approach. Equilibrium adsorption experiments were carried out at different initial dye concentrations and were successfully fitted to the Langmuir and Freundlich adsorption isotherm models. Adsorption isotherms showed maximum adsorption capacities of CTS-g-GMA-PPEGMA and chitosan of 200 mg/g and 150 mg/g, respectively, while the Langmuir equations estimated 232 mg/g and 194 mg/g, respectively. The fundamental assumptions underlying the Langmuir model may not be applicable for azo dye adsorption, which could explain the difference. The Freundlich isotherm parameters, n and K, were determined to be 2.18 and 17.7 for CTS-g-GMA-PPEGMA and 0.14 and 2.11 for chitosan, respectively. An “n” value between one and ten generally indicates favorable adsorption. The adsorption capacities of a chitosan-PPEGMA 50/50 physical mixture and pure PPEGMA were also investigated, and both exhibited significantly lower adsorption capacities than pure chitosan. In this work, CTS-g-GMA-PPEGMA proved to be more effective than its parent chitosan, with a 33% increase in adsorption capacity.