Alexandre Simula

Absolut “copper catalyzation perfected”; robust living polymerization of NIPAM: Guinness is good for SET-LRP

The controlled polymerization of N-isopropyl acrylamide (NIPAM) is reported in a range of international beers, wine, ciders and spirits utilizing Cu(0)-mediated living radical polymerization (SET-LRP). Highly active Cu(0) is first formed in situ by the rapid disproportionation of [Cu(I)(Me6-Tren)Br] in the commercial water–alcohol mixtures. Rapid, yet highly controlled, radical polymerization follows (Đ values as low as 1.05) despite the numerous chemicals of diverse functionality present in these solvents e.g. alpha acids, sugars, phenols, terpenoids, flavonoids, tannins, metallo-complexes, anethole etc. The results herein demonstrate the robust nature of the aqueous SET-LRP protocol, underlining its ability to operate efficiently in a wide range of complex chemical environments.

Aqueous Copper-Mediated Living Radical Polymerisation of N-Acryloylmorpholine, SET-LRP in Water

The polymerisation of N-acryloylmorpholine in water is reported utilising Cu(0)-mediated living radical polymerisation (SET-LRP). The inherent instability of [Cu(I) (Me6-Tren)Br] in aqueous solution is exploited via rapid disproportionation to prepare Cu(0) particles and [Cu(II) (Me6-Tren)Br2 ] in situ prior to addition of monomer and initiator. Quantitative conversion is attained within 30 min for various degrees of polymerisation (DPn = 20-640) with SEC showing symmetrical narrow molecular weight distributions (Đ < 1.18) in all cases. Optimised conditions are subsequently applied for the preparation of a diblock copolymer poly(NIPAm)-b-(N-acryloylmorpholine), illustrating the versatility of this approach.

Synthesis of well-defined α,ω-telechelic multiblock copolymers in aqueous medium: in situ generation of α,ω-diols

The synthesis of well-defined α,ω-dihydroxyl telechelic multiblock copolymers by sequential in situ chain extensions via aqueous Cu(0) mediated living radical polymerization (SET-LRP) is reported. The rapid disproportionation of Cu(I)Br in the presence of Me6-TREN in water has been exploited to generate Cu(0) and [Cu(II)Br2/Me6-TREN] in situ, resulting in rapid reaction rate and narrow molecular weight distributions. Under optimized conditions, a telechelic heptablock copolymer was obtained within 2 hours with a final dispersity of ∼1.1 while the monomer conversion was >99% for each block. A range of acrylamides and acrylates have been successfully incorporated within the same polymer backbone, including N-isopropylacrylamide (NIPAAm), N,N-diethylacrylamide (DEA) and N,N-dimethylacrylamide (DMA) and poly(ethylene glycol) methyl ether acrylate (PEGA480). The thermo-responsive nature of these materials was subsequently demonstrated via cloud point measurements as both a function of molecular weight and backbone functionality. In addition, the typically unwanted hydrolysis of the α- and ω-end groups in aqueous media was further exploited via isocyanate post-polymerization modifications to alter the end group functionality.

Copper(II) gluconate (a non-toxic food supplement/dietary aid) as a precursor catalyst for effective photo-induced living radical polymerisation of acrylates

Copper gluconate, is employed as a precursor catalyst for the photo-induced living radical polymerisation of acrylates. Optimised reaction conditions for efficient ligand transfer leads to well-defined polymers within 2 h with near quantitative conversions (>95%), low dispersities (Đ ∼ 1.16) and high end-group fidelity, as demonstrated by MALDI-ToF-MS. Additionally, in the presence of ppm concentrations of NaBr, similar degree of control could also be attained by facilitating ligand exchange, furnishing narrow dispersed polymers (Đ < 1.12).

The effect of ligand, solvent and Cu(0) source on the efficient polymerization of polyether acrylates and methacrylates in aqueous and organic media

The synthesis of well-defined telechelic polyacrylates and polymethacrylates in organic and aqueous media via Cu(0)-mediated reversible-deactivation radical polymerization is thoroughly investigated. Poly(ethylene glycol) methyl ether acrylate (PEGA480) and poly(ethylene glycol) methyl ether methacrylate (PEGMA475) are used as exemplar monomers to determine the optimum polymerization conditions for the rapid, controlled and quantitative production of both homopolymers and block copolymers. The effect of the copper source (i.e. Cu(0)-wire or Cu(0) particles), the ligand (e.g. Me6-TREN or PMDETA) and the solvent (e.g. H2O or DMSO) on the polymerization of acrylates and methacrylates has been evaluated. Kinetic experiments are performed for all polymerizations to assess the “living” behaviour of each system and method employed. In addition, in situ chain extension with another aliquot of monomer at quantitative or near quantitative conversions have been conducted as an indirect evaluation of the α,ω-Br end-groups functionality of the obtained telechelic materials. The in situ disproportionation of [CuI(L)Br] in both water and DMSO to yield Cu(0) and [CuII(L)Br]Br prior to addition of monomer and initiator and Cu(0)-wire experiments in both solvents dictate the desired polymerization protocol to use, depending on the monomer employed and highlight the weaknesses and potential of each system. Under carefully optimized conditions, narrowly distributed polyacrylates and polymethacrylates homopolymers can be obtained in a quantitative manner (>98% conversion) within 30 min of polymerization with very high end-group fidelity, exemplified by in situ chain extensions; hence highlighting the importance of the appropriate combination of the monomer with a compatible ligand, copper source, solvent and polymerization technique. For instance, well-defined polymethacrylate based block copolymers can be attained in water within 90 min with high conversion (>95% for each block) and relatively low dispersity values (Đ = 1.38).

Methacrylic Zwitterionic, Thermoresponsive, and Hydrophilic (Co)Polymers via Cu(0)-Polymerization: The Importance of Halide Salt Additives

The synthesis of hydrophilic, thermoresponsive, and zwitterionic polymethacrylates is reported by Cu(0)-mediated reversible deactivation radical polymerization in water and/or water/alcohol mixtures. The predisproportionation of [Cu(I) (PMDETA)Cl] in water prior to initiator and monomer addition is exploited to yield well-defined polymethacrylates with full monomer conversions in 30 min. The addition of supplementary halide salts (NaCl) enables the synthesis of various molecular weight poly[poly(ethylene glycol) methyl ether methacrylate] (PEGMA475) (DPn = 10-80, Mn ≈ 10,000-40 000 g mol(-1)) with full monomer conversion and narrow molecular weight distributions attained in all cases (Đ ≈ 1.20-1.30). A bifunctional PEG initiator (average Mn ≈ 1000 g mol(-1)) is utilized for the polymerization of a wide range of methacrylates including 2-dimethylaminoethyl methacrylate, 2-morpholinoethyl methacrylate, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, and 2-methacryloyloxyethyl phosphorylcholine. Despite the high water content, high end group fidelity is demonstrated by in situ chain extensions and block copolymerizations with PEGMA475 yielding well-defined functional telechelic pentablock copolymers within 2.5 h.

Synthesis of well-defined catechol polymers for surface functionalization of magnetic nanoparticles

In order to obtain dual-modal fluorescent magnetic nanoparticles, well-defined fluorescent functional polymers with terminal catechol groups were synthesized by single electron transfer living radical polymerization (SET-LRP) under aqueous conditions for “grafting to” modification of iron oxide nanoparticles. Acrylamide, N-isopropylacrylamide, poly(ethylene glycol) methyl ether acrylate, 2-hydroxyethyl acrylate, glycomonomer and rhodamine B piperazine acrylamide were homo-polymerized or block-copolymerized directly from an unprotected dopamine-functionalized initiator in an ice-water bath. The Cu-LRP tolerated the presence of catechol groups leading to polymers with narrow molecular weight distributions (Mw/Mn < 1.2) and high or full conversion obtained in a few minutes. Subsequent immobilization of dopamine-terminal copolymers on an iron oxide surface were successful as demonstrated by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), transition electron microscopy (TEM) and thermogravimetric analysis (TGA), generating stable polymer-coated fluorescent magnetic nanoparticles. The nanoparticles coated with hydrophilic polymers showed no significant cytotoxicity when compared with unmodified particles and the cellular-uptake of fluorescent nanoparticles by A549 cells was very efficient, which also indicated the potential application of these advanced nano materials for bio-imaging.

Methacrylic block copolymers by sulfur free RAFT (SF RAFT) free radical emulsion polymerisation

We demonstrate the use of sulfur free reversible addition–fragmentation chain transfer polymerisation (RAFT) as a versatile tool for the controlled synthesis of methacrylic block and comb-like copolymers. Sulfur free RAFT (SF-RAFT) utilises vinyl terminated macromonomers obtained via catalytic chain transfer polymerisation (CCTP) of methacrylates as a chain transfer agent (CTA), and thus precluding adverse aspects of the RAFT such as toxicity of dithioesters. We have synthesised a range of narrow dispersity block copolymers (Đ < 1.2) and comb-like macromolecules by employing emulsion polymerisation allowing for the preparation of relatively large quantities (∼50 g) of the above mentioned copolymers promptly and straightforwardly. Copolymers were characterised using 1H NMR, size exclusion chromatography (SEC), thermogravimetric analysis (TGA) and matrix-assisted laser desorption/ionization time of flight mass spectroscopy (MALDI-TOF-MS) techniques.

Synthesis of poly(methyl methacrylate) and block copolymers by semi-batch nitroxide mediated polymerization

In order to successfully implement the commercial synthesis of polymers by using reversible deactivation radical polymerization (RDRP) techniques in solution, semi-batch processes should be developed. However, the low monomer concentrations involved present a challenge for RDRPs. This is especially the case in the nitroxide mediated polymerization of methacrylates where, historically, even in batch control over the polymerization has been difficult. Here, we show that the alkoxyamine, 3-(((2-cyanopropan-2-yl)oxy)(cyclohexyl)amino)-2,2-dimethyl-3-phenylpropanenitrile, which was recently shown to successfully control the polymerization of methyl methacrylate and styrene, can also be used to control the polymerization of methacrylates under semi-batch conditions. High instantaneous conversions, whilst maintaining the polymer end groups are observed and the limits of control over the polymerization and the potential to synthesize block copolymers under semi-batch conditions are explored.

Novel alkoxyamines for the successful controlled polymerization of styrene and methacrylates

The design of alkoxyamine/nitroxide species capable of mediating the polymerization of both styrene and methacrylic monomers has been notoriously difficult. Herein, the nitroxide-mediated polymerization of styrene using a series of readily obtained alkoxyamines that were recently shown to control the polymerization of methyl methacrylate is presented. The robustness of the system is tested towards different temperatures and molecular weights. The influence of the substitution pattern in the nitroxide adducts on the polymerization of styrene is monitored through kinetic analyses. An alkoxyamine that can successfully mediate the homopolymerization of styrene and methyl methacrylate is presented. This alkoxyamine is subsequently utilized for the synthesis of PMMA-b-PS and PS-b-PBMA copolymers.