The reactivity of cis-3,4-bis(hydroxymethyl)cyclobutene derivatives bearing free and protected hydroxyl groups during ring-opening metathesis polymerization (ROMP) was investigated using ...ruthenium-based initiators. It was found that the ROMP of cis-4-benzyloxymethyl-3-hydroxymethylcyclobutene (1) using highly reactive initiators containing N-heterocyclic carbenes as nonlabile ligands leads to well-defined polymers while cis-3,4-bis(hydroxymethyl)cyclobutene (2) was reluctant to polymerize under the same conditions. Kinetic studies were performed to assess a number of critical reaction parameters: initiator structure, solvent, and temperature. The results demonstrate that Grubbs’ second- and third-generation catalysts are the best initiators to prepare well-defined 1,4-polybutadienes containing simultaneously free and protected hydroxyl side groups with predictable molecular weights (up to 40 000 g mol–1) and narrow molecular weight distributions. Besides, low values of k p/k i (the ratio of the rate constant of propagation to the rate constant of initiation) were found for the ROMP of monomer 1 with Grubbs’ second-generation catalyst in chloroform or THF as the solvent, demonstrating a living process. The so-obtained polymers having hydroxyl side groups are an ideal platform to prepare original well-defined graft copolymers through the grafting-from strategy.
A new versatile cyclic polymer platform for the design of advanced cyclic materials was prepared by combining ring-expansion metathesis polymerization (REMP) and click chemistry. Cyclic ...poly(norbornenyl azlactone) backbones were synthesized over an unprecedented length range with number-average degree of polymerization (DP n ) ranging from 25 to 1000. The cyclic topology was thoroughly characterized using 1H NMR, size exclusion chromatography (SEC) with multiangle light scattering (MALS) and viscometer detection. Postpolymerization modification (PPM) of these scaffolds was carried out with amino-terminated mannoses using the click aminolysis of the azlactone moiety to prepare a library of multivalent cyclic glycopolymers. The binding inhibition of the resulting cyclic glycopolymers was assessed against a panel of model and biologically relevant lectins (Bc2L-A, FimH, langerin, DC-SIGN, and ConA). The cyclic carbohydrate-functionalized polynorbornenes exhibited high lectin-binding inhibitory potency in the biochip assay, surpassing their monovalent analogues by several orders of magnitude and competing strongly with their linear polymer analogues in terms of IC50 values. Interestingly, the cyclic polymers also prevented the adhesion of Adherent-Invasive Escherichia coli implied in Crohn’s disease, to intestinal cells.
Well-defined high molar mass poly(1,4-butadiene)-g-poly(ε-caprolactone) (PBu-g-PCL) graft copolymers were prepared through the grafting-from route by the combination of ring-opening metathesis ...polymerization (ROMP) and organocatalyzed ring-opening polymerization (ROP). The synthesis route relies on the ROMP of cis-4-benzyloxymethyl-3-hydroxymethylcyclobutene initiated by ruthenium-based Grubbs’ catalysts followed by organocatalyzed ROP of ε-caprolactone initiated by the hydroxyl side groups of the backbone using 1,5,7-triazabicyclo4.4.0dec-5-ene (TBD) as the catalyst. The reported strategy provides PBu-g-PCL having a strictly poly(1,4-butadiene) backbone with the highest molar mass reported up to now (M n > 106 g mol–1). Self-assembling properties of the resulting PBu-g-PCL graft copolymer were investigated using small-angle X-ray scattering (SAXS) in toluene solution and in the solid state.
Click and drug: A combination of orthogonal click reactions is employed for the preparation of functional iron oxide nanoparticles (IONPs) that show unprecedented hyperthermia‐induced drug release ...through a magnetically stimulated retro‐Diels–Alder (rDA) process. Magnetic stimulation induces sufficient local energy in close proximity to the cycloadduct to initiate the rDA process.
The work reported here is the first study aimed at providing a full screening of a real unsortable non-recycled post-consumer WEEE stream free of brominated flame retarded plastics, separated using ...on-line X-ray detection, toward its recycling. In the existing sorting lines, up to 40% of plastics from waste electrical and electronic equipment (WEEE) stream can be rejected, herein named unsortable plastics. To have the most representative homogeneous sample for physico-chemical characterizations, a sampling method was developed to overcome the heterogeneity of the investigated 500 kg batch. The batch screening on both representative samples (∼500 μm size) and 100 plastic fractions (∼20 mm size), by means of routine techniques used in the plastic industry, has allowed to quantify reliably the main polymers included in the studied batch; ∼50% styrene-based polymers, ∼15% polypropylene (PP), ∼15% polycarbonate (PC), ∼1–4% polyamide (PA), polyethylene (PE), polyvinyl chloride (PVC), poly (ethylene terephthalate) (PET), poly (methyl methacrylate) (PMMA) and ∼8% of multi-layer plastics, paints and thermosets. The identification of the ∼8.0% inorganic phase by X-ray fluorescence spectrometry revealed the presence of several additives/charges commonly incorporated in plastic materials, such as calcium carbonate and talc. The studied batch was then subjected to electron beam irradiation at 50 and 200 kGy doses, as a means of compatibilization between the batch components. The mechanical properties and thermal behavior of irradiated samples pointed out the crucial role of the residual free radical scavenger agents present in post-consumer WEEE streams, leading to significantly different properties compared to those of irradiated virgin polymer blends highlighted in the literature.
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•First full screening of a real unsortable non-recycled post-consumer WEEE stream.•Effective characterization of 500 Kg batch from representative 3g samples.•The mechanical behavior of the irradiated batch was studied.•Residual free radical scavengers hinder the batch compatibilization via irradiation.
Well-defined, highly reactive poly(norbornenyl azlactone)s of controlled length (number-average degree of polymerization D P n ̅ = 10 to 1,000) were made by ring-opening metathesis polymerization ...(ROMP) of pure exo-norbornenyl azlactone. These were converted into glycopolymers using a facile postpolymerization modification (PPM) strategy based on click aminolysis of azlactone side groups by amino-functionalized glycosides. Pegylated mannoside, heptyl-mannoside, and pegylated glucoside were used in the PPM. Binding inhibition of the resulting glycopolymers was evaluated against a lectin panel (Bc2L-A, FimH, langerin, DC-SIGN, ConA). Inhibition profiles depended on the sugars and the degrees of polymerization. Glycopolymers from pegylated-mannoside-functionalized polynorbornene, with D P n ̅ = 100, showed strong binding inhibition, with subnanomolar range inhibitory concentrations (IC50s). Polymers surpassed the inhibitory potential of their monovalent analogues by four to five orders of magnitude thanks to a multivalent (synergistic) effect. Sugar-functionalized poly(norbornenyl azlactone)s are therefore promising tools to study multivalent carbohydrate–lectin interactions and for applications against lectin-promoted bacterial/viral binding to host cells.
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•Ring-opening metathesis polymerization of endo/exo mixture of norbornenyl azlactone.•Synthesis of polymers with azido side-chain via click postpolymerization aminolysis.•Clicking of ...azido-functional polymer by copper-catalyzed alkyne − azide cycloaddition.
Ring-opening metathesis polymerization (ROMP) of a heterofunctional azlactone-based monomer, namely norbornenyl azlactone (NBAzl), is reported for the first time using third generation ruthenium-based catalyst (G3′). It is demonstrated that ROMP of the mixture of stereoisomers of NBAzl obtained by Diels-Alder reaction between 2-vinyl-4,4-dimethyl-5-oxazolone (vinyl azlactone, VDM) and cyclopentadiene leads to well-defined polymers (Mn, SEC¯ up to 52 500 g mol−1, Ð < 1.37). The resulting polymers easily undergo click postpolymerization modification by aminolysis of the azlactone groups using amine nucleophiles. By using azido oligoethylene glycol amine, ROMP polymers having azido side-chains capable of alkyne azide click modification are prepared, that are not attainable by direct ROMP of azido-functionalized monomers. The successful clicking to the so-obtained azido-functional ROMP polymer was demonstrated by copper-catalyzed alkyne − azide cycloaddition (CuAAC) with alkyne-functionalized fluorescein. The reported versatile methodology produces with complete atom economy a platform for new functional polymer libraries, including polymer materials with potential medical and biological applications.
•Synthesis of a series of new hindered phenol-functionalized norbornenes•Kinetics of their ring-opening metathesis polymerization•Incorporation into polypropylene and a dicylopentadiene industrial ...formulation•Thermal ageing of the resulting thin films
A series of new norbornene monomers containing sterically hindered phenol groups have been synthesized and polymerized via ring-opening metathesis polymerization (ROMP) using the Grubbs 3rd generation catalyst (G3’). ROMPs exhibit first-order kinetics and molar masses increase linearly with monomer conversion and well-controlled phenol hindered-functionalized polynorbornenes were obtained with a monomer to initiator ratio up to 1 000. The first-order rate constants show that the ROMP activity is closely associated with the norbornene monomer steric congestion. The antioxidant behavior of these hindered phenol-containing polynorbornenes with different para-bridged side groups in polypropylene (PP) was estimated by onset oxidation temperature (OOT) measurements. The ability of these hindered phenol-containing norbornenes to copolymerize by ROMP with dicyclopentadiene (DCPD) was used to bound covalently the antioxidant moiety onto a polydicyclopentadiene (PDCPD) resin whose thermal ageing has been investigated.
We report the efficient synthesis of a series of new azlactone-based heterofunctional linkers bearing two orthogonal clickable groups that proceed with full atom economy. These new linkers comprise ...an azlactone (oxazolone) group that quickly reacts with amino groups in biologically relevant medium without byproduct elimination and a (bio)orthogonal handle which further undergoes facile and selective click reactions such as thiol-ene coupling, Diels-Alder or azide-alkyne cycloadditions. As an example, the application of this methodology to lysozyme PEGylation in aqueous medium is described.
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