Reassessing the Photochemical Upcycling of Polystyrene Using Acridinium Salts.

Polystyrene (PS) is a commodity plastic recalcitrant to chemical recycling or upcycling processes. Approaches aimed at deconstructing PS by photocatalytic means struggle to generate high-energy species capable of cleaving the robust C-H and C-C bonds of PS. We show that 9-mesityl-10-methylacridinium perchlorate (MA) is capable of upcycling various grades of PS substrates into up to 40 % benzoic acid (BAc), formic acid (FA) and small proportions of acetophenone (ACP), under visible light (456 nm) or through solar radiation.

An Expedient Route to Bio-Based Polyacrylate Alternatives with Inherent Post-Chemical Modification and Degradation Capabilities by Organic Catalysis for Polymerization of Muconate Esters.

The quest for polymers that would be at the same time bio-based and degradable after usage, in addition to offering chemical post-modification options, remains a daunting challenge in contemporary polymer science. Despite advances in polymer chemistry, attempts at controlling the chain-growth polymerization of muconate esters remain unexplored. Here we show that dialkyl muconates can be rapidly polymerized by organocatalyzed group transfer polymerization (O-GTP).

Exploiting the Reversible Dimerization of -Heterocyclic Carbenes to Access Dynamic Polymer Networks with an Organocatalytic Activity.

The capability of some -heterocyclic carbenes (NHCs) to reversibly dimerize is exploited to access dynamic polymer networks. Benzimidazolium motifs serving as NHC precursors have thus been supported onto copolymer chains by reversible addition-fragmentation chain transfer (RAFT) copolymerization of styrene and up to 20 mol % of 4-vinylbenzyl-ethyl-benzimidazolium chloride. Molecular versions of 1,3-dialkyl benzimidazolium salts have been synthesized as models, the deprotonation of which with a strong base yields the NHC dimers in the form of tetraaminoalkenes.

Expedient Synthesis of Thermally Stable Acyclic Amino(haloaryl)carbenes: Experimental and Theoretical Evidence of "Push-Pull" Stabilized Carbenes.

A library of novel structurally related singlet carbenes, namely, acyclic amino(haloaryl)carbenes, was designed by a high-yielding two-step procedure, and their chemical stability explored both experimentally and theoretically. Thanks to a careful selection of both the amino and the aryl substitution pattern, these carbenes exhibit a wide range of stability and reactivity, spanning from rapid self-dimerization for carbenes featuring -F substituents to very high chemical stability as bare carbenes, up to 60 °C for several hours for compounds carrying -Br substituents. Their structure was determined through NMR and X-ray diffraction studies, and their reactivity evaluated in benchmark reactions, highlighting the ambiphilic character of this novel class of singlet carbenes.

Consecutive one-pot alkyne semihydrogenation/alkene dioxygenation reactions by Pt(II)/Cu(II) single-chain nanoparticles in green solvent.

Heterobimetallic Pt(II)/Cu(II) single-chain polymer nanoparticles (SCNPs) were sequentially synthesized from a polymeric precursor featuring both α-diazo-β-ketoester and naked β-ketoester functional groups. Photoactivated carbene generation at = 365 nm from α-diazo-β-ketoester moieities was triggered for bonding Pt(II) ions from dichloro(1,5-cyclooctadiene)Pt(II) to the polymeric precursor, whereas Cu(II) ions were subsequently incorporated Cu(II)-(β-ketoester) complex formation using Cu(II) acetate. Both intrachain Pt(II) bonding and Cu(II) complexation were found to contribute to the folding of the polymeric precursor generating Pt(II)/Cu(II)-SCNPs as evidenced by infrared spectroscopy, size exclusion chromatography and dynamic light scattering.

Lanthanide-Based Single-Chain Nanoparticles as "Visual" Pass/Fail Sensors of Maximum Permissible Concentration of Cu Ions in Drinking Water.

The maximum permissible concentration (m.p.c.

Gold Nanoclusters Synthesized within Single-Chain Nanoparticles as Catalytic Nanoreactors in Water.

Metalloenzymes are able to catalyze complex biochemical reactions in cellular (aqueous) media with high efficiency. In recent years, a variety of metal-containing single-chain nanoparticles (SCNPs) have been synthesized as simplified metalloenzyme-mimetic nano-objects. However, most of the metal-containing SCNPs reported so far contained complexed metal ions but not metal nanoclusters (NCs) with diameter <5 nm, which could be used as powerful, emerging catalysts.

Group-Transfer Polymerization-Induced Self-Assembly (GTPISA) in Non-polar Media: An Organocatalyzed Route to Block Copolymer Nanoparticles at Room Temperature.

Polymerization-induced self-assembly (PISA) enables the synthesis at large scale of a wide variety of functional nanoparticles. However, a large number of works are related to controlled radical polymerization (CRP) methods and are generally undertaken at elevated temperatures (>50 °C). Here is the first report on methacrylate-based nanoparticles fabricated by group transfer polymerization-induced self-assembly (GTPISA) in non-polar media (n-heptane).

Enzymes' Power for Plastics Degradation.

Plastics are everywhere in our modern way of living, and their production keeps increasing every year, causing major environmental concerns. Nowadays, the end-of-life management involves accumulation in landfills, incineration, and recycling to a lower extent. This ecological threat to the environment is inspiring alternative bio-based solutions for plastic waste treatment and recycling toward a circular economy.

Reaching High Stereoselectivity and Activity in Organocatalyzed Ring-Opening Polymerization of Racemic Lactide by the Combined Use of a Chiral (Thio)Urea and a -Heterocyclic Carbene.

Stereochemical control during polymerization is a key strategy of polymer chemistry to achieve semicrystalline engineered plastics. The stereoselective ring-opening polymerization (ROP) of racemic lactide (-LA), which can lead to highly isotactic polylactide (PLA), is one of the emblematic examples in this area. Surprisingly, stereoselective ROP of -LA employing chiral organocatalysts has been under-leveraged.

Stimuli-responsive and core cross-linked micelles developed by NiCCo-PISA of helical poly(aryl isocyanide)s.

We report the synthesis of redox- and pH-sensitive block copolymer micelles that contain chiral cores composed of helical poly(aryl isocyanide)s. Pentafluorophenyl (PFP) ester-containing micelles synthesised nickel-catalysed coordination polymerisation-induced self-assembly (NiCCo-PISA) of helical poly(aryl isocyanide) amphiphilic diblock copolymers are modified post-polymerisation with various diamines to introduce cross-links and/or achieve stimulus-sensitive nanostructures. The successful introduction of the diamines is confirmed by Fourier-transform infrared spectroscopy (FT-IR), while the stabilisation effect of the cross-linking is explored by dynamic light scattering (DLS).

Block Copolymer Synthesis by a Sequential Addition Strategy from the Organocatalytic Group Transfer Polymerization of Methyl Methacrylate to the Ring-Opening Polymerization of Lactide.

Sequential block copolymerization involving comonomers belonging to different classes, e.g., a vinyl-type monomer and a heterocycle, is a challenging task in macromolecular chemistry, as corresponding propagating species do not interconvert easily from one to the other by crossover reactions.

Tuning the activity and selectivity of polymerised ionic liquid-stabilised ruthenium nanoparticles through anion exchange reactions.

The development of highly active and selective heterogeneous-based catalysts with tailorable properties is not only a fundamental challenge, but is also crucial in the context of energy savings and sustainable chemistry. Here, we show that ruthenium nanoparticles (RuNPs) stabilised with simple polymerised ionic liquids (PILs) based on -vinyl imidazolium led to highly active and robust nano-catalysts in hydrogenation reactions, both in water and organic media. Of particular interest, their activity and selectivity could simply be manipulated through counter-anion exchange reactions.

Direct and selective access to amino-poly(phenylene vinylenes)s with switchable properties by dimerizing polymerization of aminoaryl carbenes.

Despite the ubiquity of singlet carbenes in chemistry, their utility as true monomeric building blocks for the synthesis of functional organic polymers has been underexplored. In this work, we exploit the capability of purposely designed mono- and bis-acyclic amino(aryl)carbenes to selectively dimerize as a general strategy to access diaminoalkenes and hitherto unknown amino-containing poly(p-phenylene vinylene)s (N-PPV's). The unique selectivity of the dimerization of singlet amino(aryl)carbenes, relative to putative C-H insertion pathways, is rationalized by DFT calculations.

A chiral thiourea and a phosphazene for fast and stereoselective organocatalytic ring-opening-polymerization of racemic lactide.

Control of stereoregularity is inherent to precision polymerization chemistry for the development of functional materials. A prototypal example of this strategy is the ring-opening polymerization (ROP) of racemic lactide (rac-LA), a bio-sourced monomer. Despite significant advances in organocatalysis, stereoselective ROP of rac-LA employing chiral organocatalysts remains unexplored.

Nickel-Catalyzed Coordination Polymerization-Induced Self-Assembly of Helical Poly(aryl isocyanide)s.

The interest in helix-containing nanostructures is currently growing as a consequence of their potential applications in areas such as nanomedicine, nanomaterial design, chiral recognition, and asymmetric catalysis. Herein, we present a facile and tunable one-pot methodology to achieve chiral nano-objects. The nickel-catalyzed coordination polymerization-induced self-assembly (NiCCo-PISA) of helical poly(aryl isocyanide) amphiphilic diblock copolymers was realized and allowed access to various nano-object morphologies (spheres, worm-like micelles, and polymersomes).

Catalytically Active N-Heterocyclic Carbene Release from Single-Chain Nanoparticles Following a Thermolysis-Driven Unfolding Strategy.

The need for efficient, tailor-made catalysts has inspired chemists to design synthetic macromolecular architectures for selective catalysis. To this purpose, herein the synthesis and in-depth characterization of Ag(I)-crosslinked single-chain nanoparticles (SCNPs) is reported and their application as catalysts is demonstrated. Specifically, a copolymer of styrenic benzimidazolium chloride is synthesized as a linear precursor via reversible addition-fragmentation chain-transfer polymerization.

Bulk Organocatalytic Synthetic Access to Statistical Copolyesters from l-Lactide and ε-Caprolactone Using Benzoic Acid.

The development of synthetic strategies to produce statistical copolymers based on l-lactide (l-LA) and ε-caprolactone (CL), denoted as P(LA- stat-CL), remains highly challenging in polymer chemistry. This is due to the differing reactivity of the two monomers during their ring-opening copolymerization (ROcP). Yet, P(LA- stat-CL) materials are highly sought after as they combine the properties of both polylactide (PLA) and poly(ε-caprolactone) (PCL).

Isoselective Ring-Opening Polymerization of -Lactide from Chiral Takemoto's Organocatalysts: Elucidation of Stereocontrol.

Despite significant advances in organocatalysis, stereoselective polymerization reactions utilizing chiral organocatalysts have received very little attention, and much about the underlying mechanisms remains unknown. Here, we report that both commercially available (,)- and (,)-enantiomers of chiral thiourea-amine Takemoto's organocatalysts promote efficient control and high isoselectivity at room temperature of the ring-opening polymerization (ROP) of racemic lactide by kinetic resolution, yielding highly isotactic, semicrystalline and metal-free polylactide (PLA). Kinetic investigations and combined analyses of the resulting PLAs have allowed the stereocontrol mechanism, which eventually involves both enantiomorphic site control and chain-end control, to be determined.

Intramolecular Quaternization as Folding Strategy for the Synthesis of Catalytically Active Imidazolium-Based Single Chain Nanoparticles.

A novel synthetic strategy to single chain nanoparticles (SCNP) based on a previously unexplored intramolecular reaction as a means to autonomously fold a parent copolymer precursor is reported. The latter is a statistical styrenic-type copolymer synthesized by RAFT polymerization and is composed of four different comonomer units, including styrene, grafted poly(ethylene oxide) chains, and antagonist benzimidazol- and chlorobenzyl-based units. The two latter functions are reacted together by a quaternization reaction to spark the folding process, creating imidazolium-based cross-link points.

Fluorinated Poly(ionic liquid) Diblock Copolymers Obtained by Cobalt-Mediated Radical Polymerization-Induced Self-Assembly.

Poly(ionic liquid)s (PILs) have attracted considerable attention as innovative single-ion solid polyelectrolytes (SPEs) in substitution to the more conventional electrolytes for a variety of electrochemical devices. Herein, we report the precise synthesis, characterization, and use as single-ion SPEs of a novel double PIL-based amphiphilic diblock copolymer (BCP), i.e.

Non-Isocyanate Polyurethane Soft Nanoparticles Obtained by Surfactant-Assisted Interfacial Polymerization.

Polyurethanes (PUs) are considered ideal candidates for drug delivery applications due to their easy synthesis, excellent mechanical properties, and biodegradability. Unfortunately, methods for preparing well-defined PU nanoparticles required miniemulsion polymerization techniques with a nontrivial control of the polymerization conditions due to the inherent incompatibility of isocyanate-containing monomers and water. In this work, we report the preparation of soft PU nanoparticles in a one-pot process using interfacial polymerization that employs a non-isocyanate polymerization route that minimizes side reactions with water.

The organocatalytic ring-opening polymerization of N-tosyl aziridines by an N-heterocyclic carbene.

The ring-opening polymerization of N-tosyl aziridines, in the presence of 1,3-bis(isopropyl)-4,5(dimethyl)imidazol-2-ylidene as an organocatalyst and an N-tosyl secondary amine as initiator mimicking the growing chain, provides the first metal-free route to well defined poly(aziridine)s (PAz) and related PAz-based block copolymers.

One-Pot Synthesis of Double Poly(Ionic Liquid) Block Copolymers by Cobalt-Mediated Radical Polymerization-Induced Self-Assembly (CMR-PISA) in Water.

Amphiphilic double poly(ionic liquid) (PIL) block copolymers are directly prepared by cobalt-mediated radical polymerization induced self-assembly (CMR-PISA) in water of N-vinyl imidazolium monomers carrying distinct alkyl chains. The cobalt-mediated radical polymerization of N-vinyl-3-ethyl imidazolium bromide (VEtImBr) is first carried out until high conversion in water at 30 °C, using an alkyl bis(acetylacetonate)cobalt(III) adduct as initiator and controlling agent. The as-obtained hydrophilic poly(N-vinyl-3-ethyl imidazolium bromide) (PVEtImBr) is then used as a macroinitiator for the CMR-PISA of N-vinyl-3-octyl imidazolium bromide (VOcImBr).

Imidazolium-Based Poly(Ionic Liquid)s Featuring Acetate Counter Anions: Thermally Latent and Recyclable Precursors of Polymer-Supported N-Heterocyclic Carbenes for Organocatalysis.

Statistical copoly(ionic liquid)s (coPILs), namely, poly(styrene)-co-poly(4-vinylbenzylethylimidazolium acetate) are synthesized by free-radical copolymerization in methanolic solution. These coPILs serve to in situ generate polymer-supported N-heterocyclic carbenes (NHCs), referred to as polyNHCs, due to the noninnocent role of the weakly basic acetate counter-anion interacting with the proton in C2-position of pendant imidazolium rings. Formation of polyNHCs is first evidenced through the quantitative formation of NHC-CS2 units by chemical postmodification of acetate-containing coPILs, in the presence of CS2 as electrophilic reagent (= stoichiometric functionalization of polyNHCs).