Search

A versatile approach has been developed to prepare small mesoporous silica particles with simultaneous control of the internal ordered pore structure and the external particle surface. Mixed polyion complex (PIC) micelles are used as silica structure-directing agents: they result from the complexation of a polybase with two polyacid double-hydrophilic block copolymers (DHBC) having either a poly(ethylene oxide) (PEO) based-block or a polyacrylamide (PAM) block. The ionizable block in both DHBC is poly(acrylic acid), which complexes oligochitosan to form the core of the electrostatic complex. By varying the architecture of the PEO-based block (linear or comb-shaped) and the synthesis parameters, it is possible to modulate the pore structure from 3D cage-like to 2D-hexagonal and lamellar mesostructures. Replacing a fraction of the PEO-based polymers with DHBC having a polyacrylamide block that has no affinity for silica is shown to affect silica-micelle interactions and material growth. While the PEO chains interact with silica to form the hybrid interface, the PAM chains act as capping agents and control the external surface of the particles. Increasing the relative amount of PAM-based DHBC leads to the formation of small discrete mesoporous silica particles that are reduced in size to 200 nm. The particle size reduction and particle surface stabilization by PAM chains can be explained by considering not only the existence of a mixed corona of PAM and PEO in PIC micelles but also the differentiated solubility of these two neutral blocks induced by silica condensation. Thus, the present strategy allows independent decrease of the particle size and tuning of its pore structure. [Display omitted] • Eco-friendly synthesis of ordered mesoporous silica using polyion complex micelles of three hydrophilic polymers. • Mixed corona micelles act both as structure-directing agents and as capping agents for small ordered mesoporous particles. • Elucidation of formation mechanisms that lead to independent tuning of particle size and pore structure. [ABSTRACT FROM AUTHOR]

Modification of the biodegradable and renewable poly(lactide) (PLA) to provide functional aliphatic polyesters is highly desirable to meet application requirements. In this context, the objective of this work is to evaluate the possibility of using free-radical substitution as a simple and non-degrading method to yield the desired functional PLA. Halogenation of PLA is carried out in solution and various reaction conditions are evaluated. Halogenated PLAs are characterized by 1H NMR spectroscopy and size exclusion chromatography (SEC) to evaluate the substitution ratios and to check the non-degrading character of the radical modification. Furthermore, reactions on model compounds as well as MALDI-TOF analyses are performed to elucidate the involved mechanism. The combined results prove the free-radical halogenation of PLA in solution to be regioselective with only the ω-halogenated PLA being obtained without main-chain substitution. [ABSTRACT FROM AUTHOR]

Abstract: This study reported the sonochemical deposition of platinum on the surface of polystyrene beads (PSBs) and the transfer of obtained Pt nanoparticles into a porous silica matrix using the PSB as a sacrificial template. Platinum nanoparticle deposition was ensured by the sonochemical reduction of Pt(IV) at room temperature in latex solutions containing polystyrene beads in the presence of formic acid under Ar or under Ar/CO atmosphere without any additives. After ultrasonic treatments for few hours, well dispersed Pt nanoparticles within the range of 3–5nm deposited on PSB were obtained in both studied conditions. Samples were then mixed with TEOS, dried, and heated at 450°C to ensure the PSB removal from the silica matrix. TEM and SEM results clearly show that final silica pore size is within the same order of magnitude than initial PSB. Finally, platinum decorated silica matrix with chosen pore sizes was successfully prepared. [Copyright &y& Elsevier]

Abstract: The phase behavior of triblock and graft-type poly(dimethylsiloxane) (PDMS)–poly(ethylene oxide) (PEO) copolymer surfactants has been investigated in compressed carbon dioxide (CO2). For this purpose, cloud-point pressures have been measured in the pressure and temperature range from P =10 to 40MPa and from T =293 to 338K. The Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equation of state (EoS) has been applied to model the experimental data in order to better understand the influence of the structure of the copolymers on the phase behavior of the system. The pure-component parameters for PDMS have been fitted originally to PDMS/n-pentane system. These parameters are successfully applied for PDMS in CO2 by adjusting a temperature-dependent binary interaction parameter. The phase behavior of the triblock copolymers was successfully predicted by PC-SAFT. In contrast, the phase behavior of the graft copolymers was difficult to predict accurately at this stage. [Copyright &y& Elsevier]

Abstract: Poly(glycidyl methacrylate-co-butyl methacrylate)/poly(vinylidene chloride-co-methyl acrylate) (poly(GMA-co-BMA)/poly(VDC-co-MA)) composite latexes have been successfully synthesized via a two-stage emulsion polymerization process. In a first step, emulsion copolymerization of GMA and BMA was carried out in optimized conditions (low temperature, neutral pH, starved-feed conditions) to both limit the hydrolysis of epoxy groups and obtain small particle size (typically 30–50 nm size range). Composite latexes were then obtained by a second-stage seeded copolymerization of VDC and MA in the presence of tetrasodium pyrophosphate to control the pH and reach high molecular weight, leading to partial encapsulation of the seed particles (snow-man morphology, in agreement with theoretical expectations). Thermogravimetric analyses performed on the resulting composite particles showed that the epoxy-functionalized seed polymer behaved as an efficient thermal stabilizer of PVDC. [Copyright &y& Elsevier]

The article offers information on poly(dimethylsiloxanes) (PDMS) copolymers and explores its synthesis to functionalized polysiloxanes by radical polymerization. It discusses the synthesis of polysiloxanes using routes such as ring-opening polymerization, polycondensation, and redistribution, and cites some applications based on surface and mechanical properties and thermal stability. It states that PDMS-containing architectured copolymers can be obtained by correct polysiloxane macroinitiator.

Biobased monomers and green processes are key to producing sustainable materials. Cardanol, an aromatic compound obtained from cashew nut shells, may be conveniently functionalized, e.g., with epoxy or (meth)acrylate groups, to replace petroleum-based monomers. Photoinduced polymerization is recognized as a sustainable process, less energy intensive than thermal curing; however, cardanol-based UV-cured polymers have relatively low thermomechanical properties, making them mostly suitable as reactive diluents or in non-structural applications such as coatings. It is therefore convenient to combine them with biobased reinforcements, such as microfibrillated cellulose (MFC), to obtain composites with good mechanical properties. In this work a cardanol-based methacrylate monomer was photopolymerized in the presence of MFC to yield self-standing, flexible, and relatively transparent films with high thermal stability. The polymerization process was completed within few minutes even in the presence of filler, and the cellulosic filler was not affected by the photopolymerization process. [ABSTRACT FROM AUTHOR]

Abstract: The phase behavior of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers (PEO-PPO-PEO Pluronics) in liquid and supercritical carbon dioxide has been studied by cloud point measurements. It shows that such trade hydrocarbonated surfactants are fairly soluble (0.1wt.%) in carbon dioxide in relatively mild conditions of temperature and pressure (T <65°C, P <30MPa). An empirical model based on the molecular weight of the copolymer has been proposed to predict the pressure–temperature phase diagram for a series of Pluronics (10wt.% of ethylene oxide). Furthermore, the water/CO2 interfacial tension has been measured to investigate the interactions between water and the polar moieties of the surfactants (PEO blocks and hydroxyl end-groups) as well as the interactions between CO2 and the “CO2-philic” moiety of the surfactants (PPO block). An interfacial saturation concentration was evidenced and it was shown to depend on the temperature at a given pressure. The cloud point curves and interfacial tension data are fully consistent with a change in the affinity of the surfactant for CO2 versus pressure and temperature. A correlation between CO2-philic characteristics and surface active properties of the copolymers is given. [Copyright &y& Elsevier]

Abstract: In order to combine the properties of polymers based on vinylidene chloride (VC2) (barrier properties towards many gases) and fluorinated polymers (low surface energy, improvement of the chemical resistance), a diblock terpolymer poly(VC2-co-MA)-b-(PFDA) was synthesized by RAFT process. The first block is a statistical copolymer of vinylidene chloride (VC2) and methyl acrylate (MA) (M n=6800gmol−1 and PDI=1.4), the second block is a homopolymer of 1H,1H,2H,2H-perfluorodecyl acrylate (FDA). The diblock terpolymer, when used in a coating formulation based on a poly(VC2-co-MA) matrix, migrates towards the surface of the coating and fluorinated moieties are located at the surface. The migration of the additive was clearly shown by scanning electron microscopy EDX and by measurements of surface energy, and the influence of the nature of the solvents used to prepare the coating was clearly established. These results indicate that the driving force for the migration is the surface energy of the additive. [Copyright &y& Elsevier]

[Display omitted] • Liquid and gas phase sulfidation conditions of MoO x /PANI hybrids result in different MoS x phases. • Active CoMoS phase content in the final catalysts deposited through a surface reaction using cobalt acetylacetonate depends on the nature of starting Mo based PANI materials. The formation of mixed sites is favored when Mo and Co sulfidations are simultaneous. • CoMoS/PANI showed much better catalytic activities than the CoMoS counterpart prepared without PANI. • HDS of 3-methylthiophene is correlated to the Co/Mo edges+corners atomic ratio as well as the HDS / HYD selectivity factor. Catalytic performances of promoted CoMoS catalysts were greatly improved via a synthesis strategy based on the structuration of the active phase using self-assembled PANI (Polyaniline) nanowires followed by an addition step of cobalt acetylacetonate on oxidic or sulfided Mo-based hybrids. Taking into account the different promotion levels, slabs lengths determined by XPS and TEM, the highest rate constants normalized by mol of (MoS 2) edges+corner in the hydrodesulfurization of 3-methylthiophene were obtained when Co(acac) 2 is deposited on a MoS 3 /PANI hybrid precursor. The normalized HDS rate constants for the different samples followed the increase in Co/Mo edges+corner atomic ratios whereas an optimum for HDS/HYD selectivity in the same ratio was observed. [ABSTRACT FROM AUTHOR]

• Synthesis of a novel cardanol-based phosphonic methacrylic monomer. • Polymerization of this biobased monomer by miniemulsion radical copolymerization. • UV-curing of this biobased monomer. • Evaluation of properties of both coatings on steel substrate. To create an effective adhesion promotion for different surfaces, specific anchor groups are necessary such as phosphonic groups for metals. Biobased phosphorylated monomer from cardanol was synthesized and polymerized by UV curing or miniemulsion radical polymerization. Phosphonic ethoxy cardanol methacrylate (CMP) was synthesized from cardanol via hydroxyethylation, followed by phosphorylation radical addition of dimethyl phosphite onto the unsaturations of the C15 aliphatic chain of cardanol prior methacrylation of the hydroxyl ethoxy group. Lastly the cleavage of the phosphonate ester groups was made to generate the targeted phosphonic acid moieties as adhesion promoters. Moreover, the development of a phosphonic latex was successfully achieved by miniemulsion radical copolymerization in water with an additional redox termination to ensure quantitative monomer conversions. Phosphonic cardanol and cardanol (as reference) latexes were characterized by dynamic light scattering. The effects of cardanol derivatives on the performance of protective coatings on steel plates were evaluated in UV-cured coatings as well as in latex coatings in terms of contact angle and adhesion effectiveness. In coatings, increased hydrophobic properties were observed in fomulations containing free cardanol or cardanol methacrylate. On the other side, the incorporation of phosphonic acid groups onto cardanol significantly improved the adhesion effectiveness of the coating, whatever the film-making technique. [ABSTRACT FROM AUTHOR]

Palladium (Pd) and platinum (Pt) are extensively used as catalysts in the petrochemical and automotive industries, and due to high demand for them on the market, their recycling from spent supported catalysts is clearly needed. To assess the content of Pd and Pt in catalysts in order to establish their commercial value or to evaluate the recovery efficiency of technologies used for recycling, reliable analytical methods for determination of these elements are required. Spectrometric methods, such as inductively coupled plasma optical emission spectrometry (ICP-OES) and graphite furnace atomic absorption spectrometry (GFAAS) are powerful tools that can be employed for the determination of Pd and Pt in various sample matrices. However, these methods allow only the injection of liquid samples. In this regard, the digestion of solid sample by microwave-assisted acid extraction procedures at high pressures and temperatures is often used. In this study, a microwave acid digestion method was optimized for the extraction of Pd and Pt from spent catalysts, using a four-step program, at a maximum 200 °C. The resulting solutions were analyzed using ICP-OES, at two different wavelengths for each metal (Pd at 340.458 and 363.470 nm, and Pt at 265.945 and 214.423 nm, respectively) and using GFAAS (Pd at 247.64 nm, Pt at 265.94 nm). Five types of spent catalyst were analyzed and the standard deviations of repeatability for five parallel samples were less than predicted relative standard deviations (PRSD%) calculated using Horvitz's equation for all the analyzed samples. [ABSTRACT FROM AUTHOR]

Biobased monomers have been used to replace their petroleum counterparts in the synthesis of polymers that are aimed at different applications. However, environmentally friendly polymerization processes are also essential to guarantee greener materials. Thus, photoinduced polymerization, which is low-energy consuming and solvent-free, rises as a suitable option. In this work, eugenol-, isoeugenol-, and dihydroeugenol-derived methacrylates are employed in radical photopolymerization to produce biobased polymers. The polymerization is monitored in the absence and presence of a photoinitiator and under air or protected from air, using Real-Time Fourier Transform Infrared Spectroscopy. The polymerization rate of the methacrylate double bonds was affected by the presence and reactivity of the allyl and propenyl groups in the eugenol- and isoeugenol-derived methacrylates, respectively. These groups are involved in radical addition, degradative chain transfer, and termination reactions, yielding crosslinked polymers. The materials, in the form of films, are characterized by differential scanning calorimetry, thermogravimetric, and contact angle analyses. [ABSTRACT FROM AUTHOR]

A way to improve hydrotreatment processes is to enhance the intrinsic activity of Ni or Co promoted MoS2 catalysts that are commonly used in such reactions. The aim of this work was to investigate the impact of the presence of Pluronic® P123 as a structuring agent during the synthesis of Ni promoted MoS2 catalysts (named NiMoS) in water at room temperature. A series of analyses, i.e., X-ray diffraction (XRD), chemical analysis, inductively coupled plasma mass spectrometry (ICP-MS), nitrogen adsorption-desorption isotherms, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), helped in characterizing the NiMoS-P123 and NiMoS catalysts, the latter being prepared in the absence of polymer. Both compounds contained MoS2 phase (~85 atomic% considering Mo atoms), a similar amount of mixed Ni-Mo-S phase (40–50% considering Ni) and some amount of NiS and Ni-oxidized impurity phases. The main differences between the two catalysts were a much larger specific surface area (126 m2·g−1 instead of 31 m²·g−1) and a better dispersion of the active phase as shown by the lower slab stacking (2.7 instead of 4.8) for NiMoS-P123, and the presence of C in NiMoS-P123 (9.4 wt.% instead of 0.6 wt.%), indicating an incomplete decomposition of the polymer during thermal treatment. Thanks to its larger specific surface area and lower slab stacking and therefore modification of active Mo site properties, the compound prepared in the presence of Pluronic® P123 exhibits a strong increase of the catalytic activity expressed per Mo atom for the transformation of 3-methylthiophene. Such improvement in catalytic activity was not observed for the transformation of benzothiophene likely due to poisonous residual carbon which results from the presence of Pluronic® P123 during the synthesis. [ABSTRACT FROM AUTHOR]

Eugenol, a natural phenol currently mainly obtained from clove oil, is an interesting aromatic building block for the synthesis of novel biobased monomers. It can also be obtained from lignin depolymerization, becoming a promising building block due to lignin availability as biomass feedstock. The synthesis of eight monomers derived from eugenol containing polymerizable functional groups is achieved. The (meth)acrylation of eugenol, isoeugenol, and dihydroeugenol is performed and the solution homopolymerization of these biobased monomers is studied. Moreover, aiming to prepare functional polymers, the introduction of epoxy and cyclic carbonate groups is executed via modification of the allylic double bond present in eugenol derived methacrylate. Thus, a novel platform of versatile biobased monomers derived from eugenol is presented, opening the opportunity to use them in a wide range of polymerization processes and applications [ABSTRACT FROM AUTHOR]

This work presents supramolecular coassembled nucleobase copolymers with transitional morphologies upon pH changes (from 7.4 to 10). Uracil- and adenine-containing copolymers were prepared by RAFT, which allowed us to finely tailor the polymerization degree and the composition. The coassembled formulations prepared in an aqueous buffer at two distinct pH (7.4 and 10) formed spherical morphologies at physiological pH. The increase of the pH induced the apparition of various large, irreversible anisotropic supramolecular architectures. Isothermal titration calorimetry revealed that the coassembly at pH 7.4 was mainly guided by H-bonds between complementary nucleobases, while the experiments conducted at pH 10 showed that the assemblies were mainly driven by hydrophobic interactions. These results highlight that the nature of supramolecular interactions (H-bonds or hydrophobic interactions) has a great influence on the morphology of nucleobase-containing coassemblies when changing the pH. These findings may provide further perspectives in the field of advanced nanomaterials.

A novel-biobased latex was synthesized by redox-initiated emulsion copolymerization of ethoxy dihydroeugenyl methacrylate with 5 wt % of a photosensitive methacrylate containing a coumarin group. A stable copolymer latex having 16 wt % solids content and a particle size of 53 nm was obtained. The copolymer had a T g of 29 °C and was soluble in acetone. Coatings were obtained, and the effect of UVA irradiation was tested: the light-induced cross-linking of the copolymer by [2 + 2] cycloaddition of the coumarin pendant moieties was demonstrated by UV-visible spectroscopy. As a consequence of UVA-induced cross-linking, the copolymer became insoluble in acetone. The copolymer latex was combined with hemp-derived nanocellulose to obtain composite self-standing films by simple mixing in an aqueous medium followed by casting, evaporation of water, and hot pressing. The composite films were also successfully cross-linked by [2 + 2] cycloaddition, with an enhancement of barrier properties. The water vapor transmission rate of the cross-linked composite films with up to 45 wt % nanocellulose was 5 times lower than that of the hemp nanocellulose film, while further addition of nanocellulose increased permeability., Competing Interests: The authors declare no competing financial interest., (© 2024 American Chemical Society.)

Supercritical CO 2 (scCO 2 ) extraction assisted by complexing copolymers is a promising process to recover valuable metals from lithium-ion batteries (LIBs). CO 2 , in addition to being non-toxic, abundant and non-flammable, allows an easy separation of metal-complexes from the extraction medium by depressurization, limiting the wastewater production. In this study, CO 2 -philic gradient copolymers bearing phosphonic diacid complexing groups (poly(vinylbenzylphosphonic diacid-co-1,1,2,2-tetrahydroperfluorodecylacrylate), p(VBPDA-co-FDA)) were synthesized for the extraction of lithium and cobalt from LiCoO 2 cathode material. Notably, the copolymer was able to play the triple role of leaching agent, complexing agent and surfactant. The proof of concept for leaching, complexation and extraction was achieved, using two different extraction systems. A first extraction system used aqueous hydrogen peroxide as reducing agent while it was replaced by ethanol in the second extraction system. The scCO 2 extraction conditions such as extraction time, temperature, functional copolymer concentration, and the presence of additives were optimized to improve the metals extraction from LiCoO 2 cathode material, leading to an extraction efficiency of Li and Co up to ca. 75 % at 60 °C and 250 bar., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In order to contribute to the shift from petro-based chemistry to biobased chemistry, necessary to minimize the environmental impacts of the chemical industry, 2-methoxy-4-vinylphenol (4-vinyl guaiacol, 4VG) was used to synthesize a platform of biobased monomers. Thus, nine biobased monomers were successfully prepared. The synthesis procedures were investigated through the green metrics calculations in order to quantify the sustainability of our approaches. Their radical homopolymerization in toluene solution initiated by 2,2'-azobis(2-methylpropionitrile) (AIBN) was studied and the effect of residual 4VG as a radical inhibitor on the kinetics of polymerization was also explored. The new homopolymers were characterized by proton nuclear magnetic resonance ( 1 H-NMR) spectroscopy, size exclusion chromatography and thermal analyses (dynamical scanning calorimetry DSC, thermal gravimetric analysis TGA). By varying the length of the alkyl ester or ether group of the 4VG derivatives, homopolymers with T g ranging from 117 °C down to 5 °C were obtained. These new biobased monomers could be implemented in radical copolymerization as substitutes to petro-based monomers to decrease the carbon footprint of the resulting copolymers for various applications.

Precious metals such as palladium (Pd) have many applications, ranging from automotive catalysts to fine chemistry. Platinum group metals are, thus, in massive demand for industrial applications, even though they are relatively rare and belong to the list of critical materials for many countries. The result is an explosion of their price. The recovery of Pd from spent catalysts and, more generally, the development of a circular economy process around Pd, becomes essential for both economic and environmental reasons. To this aim, we propose a sustainable process based on the use of supercritical CO 2 (i.e., a green solvent) operated in mild conditions of pressure and temperature ( p = 25 MPa, T = 313 K). Note that the range of CO 2 pressures commonly used for extraction is going from 15 to 100 MPa, while temperatures typically vary from 308 to 423 K. A pressure of 25 MPa and a temperature of 313 K can, therefore, be viewed as mild conditions. CO 2 -soluble copolymers bearing complexing groups, such as pyridine, triphenylphosphine, or acetylacetate, were added to the supercritical fluid to extract the Pd from the catalyst. Two supported catalysts were tested: a pristine aluminosilicate-supported catalyst (Cat D) and a spent alumina supported-catalyst (Cat A). An extraction conversion of up to more than 70% was achieved in the presence of the pyridine-containing copolymer. The recovery of the Pd from the polymer was possible after extraction, and the technological and economical assessment of the process was considered.

Biobased materials, derived from biomass building blocks, are essential in the pursuit of sustainable materials. Eugenol, a natural phenol obtained from clove oil, but also from lignin depolymerization, possesses a chemical structure that allows its easy modification to obtain a broad and versatile platform of biobased monomers. In this Perspective, an overview of the variety of reactions that have been executed on the allylic double bond, phenol hydroxyl group, aromatic ring, and methoxy group is given, focusing our attention on those to obtain monomers suitable for different polymerization reactions. Furthermore, possible applications and perspectives on the eugenol-derived materials are provided.

Biobased monomers derived from eugenol were copolymerized by emulsion polymerization to produce latexes for adhesive applications. Stable latexes containing ethoxy dihydroeugenyl methacrylate and ethoxy eugenyl methacrylate with high total solids content of 50 wt % were obtained and characterized. Latexes synthesis was carried out using a semibatch process, and latexes with particle diameters in the range of 159-178 nm were successfully obtained. Glass transition temperature values of the resulting polymers ranged between -32 and -28 °C. Furthermore, tack and peel measurements confirmed the possibility to use these latexes in adhesive applications.

Although metathesis photoinduced catalysis is now well established, there is little development in thin film preparation using photochemically activated ring-opening metathesis polymerization (ROMP). Herein, a N-heterocyclic carbene (NHC) photogenerator (1,3-bis(mesityl)imidazolium tetraphenylborate) is combined with an inactive metathesis catalyst ([RuCl 2 ( p -cymene)] 2 ) to generate under UV irradiation an active catalyst ( p -cymene)RuCl 2 (NHC), that is capable of producing in a single step cross-linked copolymer films by ROMP of norbornene with dicyclopentadiene. The study shows that the photoinitiated catalytic system can be optimized by increasing the yield of photogenerated NHC through a sensitizer (2-isopropylthioxanthone), and by choosing [RuI 2 ( p -cymene)] 2 as precatalyst to provide a long-term photolatency. The cross-linked polymer structure is investigated by a range of techniques including gel content measurement, FT-IR and solid-state 13 C NMR spectroscopy, TGA and DSC, which reveal a cross-linking mechanism proceeding through both metathesis and olefin coupling., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Although N-heterocyclic carbenes (NHCs) have brought profound changes in catalytic organic synthesis, their generation generally requires an inert atmosphere and harsh conditions. To overcome these limitations, an air-stable NHC photogenerator has been developed involving two mild components: 1,3-bis(mesityl)imidazolium tetraphenylborate (IMesH + BPh 4 - ) and electronically excited isopropylthioxanthone (ITX). In this study, the photochemical mechanism is investigated via the accurate identification of the transient species and photoproducts. Electron transfer reaction between the excited triplet state of ITX and BPh 4 - is demonstrated as being the primary photochemical step. Nanosecond laser spectroscopy shows an efficient quenching and the formation of the expected ITX radical anion. The oxidized borane species is not observed, suggesting that this short-lived species could dissociate very rapidly to give the phenyl radical - successfully identified using electron paramagnetic resonance - and triphenylborane. As regards the final photoproducts, 1 H and 13 C NMR spectroscopies support the formation of the targeted NHC, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), suggesting the occurrence of a subsequent proton transfer reaction between ITX radical anion and imidazolium cation (IMesH + ). Gas chromatography-mass spectrometry reveals three other products: biphenyl, isopropylthioxanthene and ITX. Their formation can be reconciled with a 2-step mechanism of photoinduced electron/proton transfer reactions. 11 B NMR spectroscopy demonstrates that the main organoboron photoproduct is diphenylborinic acid formed by oxidation of BPh 3 . Due to its Lewis acidity, Ph 2 BOH can react with IMes to yield an NHC-boron adduct.

Ordered mesoporous silica materials were prepared under different pH conditions by using a silicon alkoxide as a silica source and polyion complex (PIC) micelles as the structure-directing agents. PIC micelles were formed by complexation between a weak polyacid-containing double-hydrophilic block copolymer, poly(ethylene oxide)- b -poly(acrylic acid) (PEO- b -PAA), and a weak polybase, oligochitosan-type polyamine. As both the micellization process and the rate of silica condensation are highly dependent on pH, the properties of silica mesostructures can be modulated by changing the pH of the reaction medium. Varying the materials synthesis pH from 4.5 to 7.9 led to 2D-hexagonal, wormlike or lamellar mesostructures, with a varying degree of order. The chemical composition of the as-synthesized hybrid organic/inorganic materials was also found to vary with pH. The structure variations were discussed based on the extent of electrostatic complexing bonds between acrylate and amino functions and on the silica condensation rate as a function of pH.

Despite the versatility of periodic mesoporous organosilicas (PMOs), the bactericide capacity of these hybrid platforms has seldom been explored. Herein, we describe the synthesis of large-pore phenylene-bridged PMOs, mesostructured by polyion complex (PIC) micelles (PICPMOs) incorporating an antibiotic, neomycin B. A key feature of this approach is that the bioactive molecules are directly encapsulated within the PICPMOs during their formation. The engineered PICPMOs exhibit a well-ordered hexagonal mesophase with a molecular-scale crystallinity and large mesopores (8 nm), which facilitates pH-triggered delivery of the drug. The results obtained with a pathogenic Escherichia coli strain clearly demonstrate the potential of such PICPMOs for antibacterial applications.

We report a method to generate the N-heterocyclic carbene (NHC) 1,3-dimesitylimidazol-2-ylidene (IMes) under UV-irradiation at 365 nm to characterize IMes and determine the corresponding photochemical mechanism. Then, we describe a protocol to perform ring-opening metathesis polymerization (ROMP) in solution and in miniemulsion using this NHC-photogenerating system. To photogenerate IMes, a system comprising 2-isopropylthioxanthone (ITX) as the sensitizer and 1,3-dimesitylimidazolium tetraphenylborate (IMesH + BPh4 - ) as the protected form of NHC is employed. IMesH + BPh4 - can be obtained in a single step by anion exchange between 1,3-dimesitylimidazolium chloride and sodium tetraphenylborate. A real-time steady-state photolysis setup is described, which hints that the photochemical reaction proceeds in two consecutive steps: 1) ITX triplet is photo-reduced by the borate anion and 2) subsequent proton transfer takes place from the imidazolium cation to produce the expected NHC IMes. Two separate characterization protocols are implemented. Firstly, CS2 is added to the reaction media to evidence the photogeneration of NHC through formation of the IMes-CS2 adduct. Secondly, the amount of NHC released in situ is quantified using acid-base titration. The use of this NHC photo-generating system for the ROMP of norbornene is also discussed. In solution, a photopolymerization experiment is conducted by mixing ITX, IMesH + BPh4 - , [RuCl2(p-cymene)]2 and norbornene in CH2Cl2, then irradiating the solution in a UV reactor. In a dispersed medium, a monomer miniemulsion is first formed then irradiated inside an annular reactor to produce a stable poly(norbornene) latex.

Photoinitiated ring-opening polymerization of l-lactide (L-LA) using a photobase generator (PBG) able to release 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) is reported. Polymerization using the PBG with ketoprofenate counteranion (TBDH + .keto - ) was studied in dichloromethane either in the presence or in the absence of 1-butanol as initiator. In both cases, full monomer conversion was reached at room temperature after 10 min of irradiation at 254 nm. In the presence of 1-butanol, linear poly(L-LA) chains (PLA) were obtained, as confirmed by 1 H NMR and MALDI-TOF analyses. The polymerization was well controlled as attested by the production of polymers with low dispersity ( Đ < 1.26) and by the linear evolution of molecular weights with the quantity of initiator. Without 1-butanol, although MALDI-TOF analyses revealed cyclic PLA chains (actually formed in situ during MALDI-TOF analysis), linear PLA chains were formed as proven by 1 H NMR, viscosity measurement, and phosphitylation titration. This fast and "on demand" polymerization opens the way to biodegradable UV coatings.

Using aminoglycoside antibiotics as drug models, it was shown that electrostatic complexes between hydrophilic drugs and oppositely charged double-hydrophilic block copolymers can form ordered mesophases. This phase behavior was evidenced by using poly(acrylic acid)-block-poly(ethylene oxide) block copolymers in the presence of silica precursors, and this allowed preparing drug-loaded mesoporous silica directly from the drug-polymer complexes. The novel synthetic strategy of the hybrid materials is highly efficient, avoiding waste and multistep processes; it also ensures optimal drug loading and provides pH-dependence of the drug release from the materials.