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High molecular weight (HMW) poly(butyl acrylate)s (PBAs) and diblock copolymers consisting of PBA blocks were synthesized by ab initio emulsion polymerization using water-soluble organotellurium ch...

A new alkoxyamine based on a highly thermally stable nitroxide is used for the controlled polymerization of styrene and butyl acrylate at temperatures up to 200 °C. High monomer conversions are reached in a few minutes with a linear increase in polymer chain-length with conversion, a final dispersity (Đ) of ∼1.2, and successful chain-extension of the resulting material. The alkoxyamine concentration was altered to target various chain lengths, with autopolymerization dictating the polymerization rate of styrene regardless of alkoxyamine concentration. Controlled polymerization of methacrylate monomers and acrylic acid was successful with the addition of styrene. The new material opens the possibility to increase the range of specialty products made for applications in coatings, inks, overprint varnishes, and adhesives.

In this report, we demonstrate the use of a thermoresponsive ligand for the ruthenium-catalyzed living radical polymerization of butyl methacrylate (BMA) in miniemulsion. A phosphine-ligand-functionalized polyethylene glycol chain (PPEG) in conjunction with a Cp*-based ruthenium complex (Cp*: pentamethylcyclopentadienyl) provided thermoresponsive character as well as catalysis for living polymerization: the complex migrated from the water phase to the oil phase for polymerization upon heating and then migrated from the oil to water phase when the temperature was decreased to quench polymerization. Consequently, simple treatment (i.e., water washing or methanol reprecipitation) yielded metal-free polymeric particles containing less than 10 μg/g (by ICP-AES) of ruthenium residue.

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.

Emulsion polymerization was implemented using a CO2-switchable water-soluble organic tellurium (Te) transfer agent. Polymerization was performed under visible light irradiation conditions, thus pro...

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)...

Modification of starch nanoparticles (SNP) was conducted with styrene oxide (STO) to change their hydrophilic/hydrophobic character. Unmodified SNP and modified SNP-STO were investigated as Pickering stabilizers in miniemulsion polymerization and emulsion polymerization. The influence of varying the degree of substitution (DS) was explored in terms of interfacial activity with saturated analogues of the monomers used to prepare the miniemulsions. Pickering miniemulsion stability tests conducted with styrene, methyl methacrylate and butyl acrylate showed no apparent coalescence when using SNP-STO (DS 0.10). Pickering miniemulsion polymerization results (using the oil-soluble Vazo-52 initiator) suggest a synergistic stabilization effect between styrene and SNP-STO due to interactions between the aromatic rings present on both styrene and modified SNP-STO. Pickering emulsion polymerizations prepared using persulfate initiator and SNP-STO exhibited additional colloidal stability compared to the miniemulsions, likely provided by the persulfate anions.

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 (

The phosphonated methacrylate dimethyl(methacryloyloxy)methyl phosphonate (MAPC1) was polymerised via nitroxide-mediated polymerisation (NMP). Kinetic monitoring of the NMP of MAPC1 (with 10 mol% of styrene as comonomer) initiated with the SG1-terminated alkoxyamine (BlocBuilder) demonstrated good control of the polymerisation. Poly(dimethyl(methacryloyloxy)methyl phosphonic acid) (hPMAPC1) was obtained by deprotection of the SG1-capped PMAPC1. The “living” polymers were then grafted to the polysaccharide chitosan (CTS) to prepare a biohybrid material, in order to modify the chitosan properties with the specific properties of the phosphorus-based polymers. A grafting from strategy was also investigated by reacting MAPC1 and hMAPC1 monomers with a macroalkoxyamine-functionalised CTS in aqueous media yielding up to 35 wt% of grafted polymer. PMAPC1 and hPMAPC1 possess attractive properties, such as being fire retardant and anticorrosive and having specific affinity for metallic ions including rare earth metals. The graft-modified CTS may be a promising candidate for applications related to (waste)water treatment, anticorrosion coatings or flame retardancy.

CO2-responsive polymers with high nitrogen to carbon ratios were tested as potential forward osmosis draw solutes in a forward osmosis/ultrafiltration process. Aqueous solutions of these polymers have the potential to produce high osmotic pressures in the presence of CO2 (up to 67 bar) but exhibit dramatically lower osmotic pressures under air. Purifying the polymer by dialysis to remove lower molecular mass materials significantly reduces the osmotic pressure under air without greatly lowering the osmotic pressure under CO2.

Bio-based Pickering emulsifiers are a nontoxic alternative to surfactants in emulsion formulations and heterogenous polymerizations. Recent demand for biocompatible and sustainable formulations has accelerated academic interest in polysaccharide-based nanoparticles as Pickering emulsifiers. Despite the environmental advantages, the inherent hydrophilicity of polysaccharides and their nanoparticles limits efficiency and application range. Modification of the polysaccharide surface is often required in the development of ultrastable, functional, and water-in-oil (W/O) systems. Complex surface modification calls into question the sustainability of polysaccharide-based nanoparticles and is identified as a significant barrier to commercialization. This review summarizes the use of nanocelluloses, -starches, and -chitins as Pickering emulsifiers, highlights trends and best practices in surface modification, and provides recommendations to expedite commercialization.

A new approach was designed to prepare both hydrophobic and hydrophilic polymers by organocatalyzed atom transfer radical polymerization (O-ATRP). The method is based on using a recoverable photocatalyst whose properties can be switched using only CO2 addition and removal as triggers. The effectiveness of the CO2-switching approach in O-ATRP is demonstrated using a new CO2-switchable photoinitiated catalyst, which can be extracted from the polymer and reused. The residual catalyst in the polymer is reduced to less than 15 ppb. The feasibility of recovering and reusing the photoinitiated catalyst for subsequent polymerizations is also established.

Carbon dioxide has emerged as a new and innovative “trigger” for stimuli-responsive materials. It is abundant, inexpensive, nontoxic, and environmentally benign. Carbon dioxide-switchable polymers ...

Polystyrene-b-[polystyrene-r-poly(acrylic acid)] block-random copolymers have been synthesized at various molecular weights (7000–23 200 g/mol) and with compositions between 6 and 39 mol % acrylic ...

Starch nanoparticles (SNPs) were used to partially replace petroleum-based polymers in a biobased latex adhesive application. Modification of SNPs (i.e., increasing cross-link density, functionalizing using a sugar-based monomer, and tuning SNP hydrophobicity) was performed prior to their incorporation in a semibatch emulsion polymerization to produce stable SNP-based latexes. SNP loadings and latex solids content were varied to study their effect on latex stability and properties (e.g., viscosity, particle size, adhesive properties, particle morphology). Stable and low viscosity latexes with up to 45 wt % SNP loadings and 55 wt % latex solids were achieved. STEM images confirmed the presence of the core–shell morphology, where SNPs were located in the particle cores and provided biocontent, while the acrylic polymers were present as the shell and governed the application properties. Pushing the limits of SNP loading and latex solids was shown to come at a cost to adhesive and other properties.

ω-Hydroxytetradecanoic acid (ω-HOC14), prepared via an efficient yeast-catalyzed ω-hydroxylation of the corresponding fatty acid, was converted in two steps to the polymerizable zwitteronic surfact...

Polymerisation of dialkylaminoethyl methacrylates by reversible deactivation radical polymerisation (RDRP) provides a route for the synthesis of block polymers or macro-initiators/macro-chain transfer agents for subsequent grafting onto various substrates. While ATRP and NMP can be used to polymerise these monomers, limitations have been reported. With ATRP, the monomers have a strong affinity for the copper-based catalysts, compromising the livingness of the polymerisation. Additionally, polar solvents often cannot be employed due to solubility limitations or side reactions. In the case of NMP, a comonomer (usually styrene) is necessary to achieve good control for the polymerisation of methacrylates. RAFT-mediated polymerisation offers advantages for amino-containing monomers, yielding pure homopolymers in well controlled polymerisations. In this work, we report for the first time on the polymerisation of dialkylaminotethyl methacrylates in tert-butanol, where good control and livingness were confirmed by GPC-UV-RI analysis and chain extension experiments.

Ring-opening metathesis polymerization (ROMP) of 1,5-cyclooctadiene (COD) in miniemulsion was conducted utilizing a water-soluble TEGylated ruthenium alkylidene catalyst that was designed to underg...

We have designed three approaches to remove copper catalyst and recycle the ligands after atom transfer radical polymerizations, all based on using materials whose properties can be switched using only CO2 and any nonacidic gas (e.g., air, nitrogen, and argon) as triggers. The first approach involves use of a CO2-switchable solvent (Cy2NMe, N,N-dicyclohexylmethylamine) as the medium for the ATRP reaction. After addition of water to the polymerized reaction mixture and sparging with CO2, the polymer precipitates while the copper salt remains in the solvent. The second approach involves using a conventional ATRP solvent such as toluene to conduct the polymerization. Following polymerization, addition of water and CO2 sparging result in the ligand (Me6TREN) and copper salt transferring into the aqueous phase, while the polymer remains in the organic phase. Finally we demonstrate the effectiveness of the approach in ARGET ATRP using less ligand and copper salt. Residual copper in the polymer was

Cellulose nanocrystals (CNCs) were converted into a CO

Starch nanoparticles (SNPs) are chosen as renewable alternatives to partially replace petroleum-based monomers and produce bio-based latexes for adhesive applications. To maintain adhesive performance, SNPs are modified (i.e., via increasing cross-link density, vinyl functionalization, and adjusting hydrophilic/hydrophobic balance) to facilitate their incorporation into the latex particles. The modified SNPs are then polymerized in a semi-batch emulsion polymerization at 60 °C, and yield low viscosity latexes with up to 17 wt% SNP loading and 42 wt% solids. TEM/STEM imaging is performed and reveals the presence of a core-shell particle morphology. This is supported by comparing the adhesive properties of SNP-containing latex films from an in situ preparation vs. a blend of acrylic latex with SNPs. The results suggest that the modified SNPs were largely encapsulated into the latex particles rather than in the aqueous phase or at the latex particle/water interface.

We report a mechanistic study of the microsuspension polymerization of styrene stabilized by cellulose nanocrystals (CNCs) in its native form as well as graft-modified with copolymers of styrene an...

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.

Because oil- or solvent-based coatings (e.g. paints, varnishes, sealants) emit volatile organic compounds (VOCs), replacement with aqueous coating formulations is desirable. However, water-based (latex) coatings which are dispersions of polymer particles, are out-performed by solvent-based coatings in hardness, durability, gloss and cold-weather application. The challenge with latexes is that discrete polymer particles must coalesce to form a complete film, a complex process that often leads to imperfections in the coating. Proof-of-concept results show that CO2-responsive copolymers can form the basis of a water-borne coating in which the polymer is fully dissolved before application and yet water-resistant after application to a surface. These polymers are insoluble in neutral water, but dissolve fully in carbonated water. When a carbonated solution of polymer is cast onto a substrate, the subsequent loss of CO2 and water by evaporation results in a clear, continuous water-resistant coating. With further development, these new coatings may retain the VOC-free advantage of water-based coatings while eliminating the need for coalescence of particles.

Green chemistry seeks to reduce the environmental impact of chemical products and processes through waste reduction and the use of safer solvents and substances. Chromatographic separation in particular generates significant amounts of harmful organic solvents, acids, bases, and salts, as waste by-products. CO2-modified solvents have been reported as promising routes to the development of greener analytical methodologies, but normally with stationary phases that are inert to the chemical effects of the CO2 modifier. We now report the impact of pH and dissolved CO2 mobile phase concentration on separations that utilize primary, secondary and tertiary amine functionalized silica particles. Ibuprofen, naproxen and ketoprofen, chosen as examples of pharmaceutical analytes containing carboxylic acid groups, have now been separated with CO2-modified (carbonated) water. Chromatographic retention, selectivity and zeta potential are utilized to demonstrate a dynamic ion exchange mechanism involving both protonation and deprotonation of stationary phase and analyte functional groups. Primary and secondary amine functionalized columns retain the test carboxylic acid compounds more strongly (tR ≥ 15 min), suggesting that they are beneficial for separations requiring higher retention. The use of CO2-modified mobile phases has the potential to significantly reduce both solvent and permanent acid use in some chromatographic separations.

We report a membrane that can be reversibly switched between a hydrophilic state and a hydrophobic state simply by alternately bubbling CO2 into and passing electric potential (EP) through a solution in contact with the membrane. The prepared membrane could be effectively used for oil/water separation.

We report the use of a bio-sourced Pickering emulsifier based on cellulose nanocrystals (CNCs) grafted with less than 25 wt% of synthetic, CO2-responsive polymer for the reversible emulsification/demulsification of oil and water. CO2-responsive CNCs were previously prepared by grafting poly(N-3-(dimethylamino) propyl methacrylamide) (PDMAPMAm) and poly(N,N-(diethylamino)ethyl methacrylate) (PDEAEMA) to the CNC surface using nitroxide-mediated polymerisation (NMP) in water as a benign solvent. The surface and interfacial properties of the graft-modified CNC were characterised by surface and interfacial tensiometer measurements, and the resulting droplets obtained from emulsions were visualised using optical microscopy. The emulsification/demulsification process was found to be responsive to N2 and CO2, reversible and easily repeatable. The Pickering emulsifiers could be recovered after application, which would make this technology particularly interesting for oil–water separation and enhanced oil recovery. The pKaH of the grafted polymer and the polarity were correlated to the CO2 sparging time required to break the emulsion and to the emulsion stability (lifetime). The effects of the chain length of the grafted polymer, graft densities, total amount of CO2-switchable groups on the CNC surface, and concentration of Pickering stabiliser on the properties of emulsions were investigated.