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See detailChemo- and regio-selective additions of nucleophiles to cyclic carbonates for the preparation of self-blowing non-isocyanate polyurethane foams
Monie, Florent ULiege; Grignard, Bruno ULiege; Thomassin, Jean-Michel ULiege et al

in Angewandte Chemie International Edition (in press)

Polyurethane (PU) foams are indisputably daily essential materials found in many applications, notably for comfort (e.g. matrasses) or energy saving (e.g. thermal insulation). Today, greener routes for ... [more ▼]

Polyurethane (PU) foams are indisputably daily essential materials found in many applications, notably for comfort (e.g. matrasses) or energy saving (e.g. thermal insulation). Today, greener routes for their production are intensively searched for avoiding the use of toxic isocyanates. We now describe an easily scalable process for the simple construction of self-blown isocyanate-free PU foams by exploiting the organocatalyzed chemo- and regio-selective additions of amines and thiols to easily accessible cyclic carbonates. These reactions are first validated on model compounds and rationalized by DFT calculations. Various foams are then prepared and characterized in terms of morphology and mechanical properties, and the scope of the process is illustrated by modulating the composition of the reactive formulation. Due to the impressive diversity and accessibility of the main components of the formulations, this new robust and solvent- free process is opening avenues for constructing more sustainable PU foams, and offers the first realistic alternative to the traditional isocyanate route. Introduction [less ▲]

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See detailAdvancing the synthesis of isocyanate-free poly(oxazolidones)s: scope and limitations
Habets, Thomas ULiege; Siragusa, Fabiana ULiege; Grignard, Bruno ULiege et al

in Macromolecules (in press)

Poly(oxazolidone) is an emerging class of polyur- ethanes (PUs) that is easily accessible by an isocyanate-free pathway via the step-growth copolymerization of CO2-based monomers (bis(α-alkylidene cyclic ... [more ▼]

Poly(oxazolidone) is an emerging class of polyur- ethanes (PUs) that is easily accessible by an isocyanate-free pathway via the step-growth copolymerization of CO2-based monomers (bis(α-alkylidene cyclic carbonate)s) with primary diamines at room temperature. Here, we explore the scope and limitation of this process by investigating the influence of the diamine and the reaction conditions on the structure and macromolecular parameters of the polymer. Less hindered diamines (aliphatic and benzylic) provide selectively poly- (hydroxyoxazolidone)s, whereas the bulkier ones (cycloaliphatic) furnish polymer chains bearing two types of linkages, oxo- urethane and hydroxyoxazolidone ones. The increase of the reaction temperature or the addition of DBU as a catalyst enables to accelerate the polymerizations. The quantitative polymer dehydration is also achieved by refluxing in acetic acid, providing a new class of unsaturated poly(oxazolidone)s composed of α-alkylidene oxazolidone linkages (for hindered polymers) or a mixture of α- and β-alkylidene oxazolidone linkages (for the less hindered ones). These unsaturated poly(oxazolidone)s present a high glass transition temperature (90 °C ≤ Tg ≤ 130 °C) and a remarkable thermal stability (Td > 360 °C), rendering these polymers attractive for applications requiring high temperatures. This work is therefore opening an avenue to novel functional isocyanate-free PUs, with the pendant hydroxyl or olefin groups that are expected to be easily derivatized. [less ▲]

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See detailImpregnation of mesoporous silica with poor aqueous soluble molecule using pressurized carbon dioxide: is the solubility in the supercritical and subcritical phase a critical parameter?
Koch, Nathan ULiege; Jennotte, Olivier ULiege; Grignard, Bruno ULiege et al

in European Journal of Pharmaceutical Sciences (2020), 150

Recently, mesoporous silica (MS) has been used as a material able to maintain amorphous state of active compounds and therefore, enhance the oral bioavailability of BCSII drugs. Among impregnation methods ... [more ▼]

Recently, mesoporous silica (MS) has been used as a material able to maintain amorphous state of active compounds and therefore, enhance the oral bioavailability of BCSII drugs. Among impregnation methods of MS, techniques using supercritical carbon dioxide (sc-CO2) are promising tools. Solubility of compounds in sc-CO2 is reported as one of the most critical parameters, which usually limits its use in drug formulation. Indeed, most of compounds have poor solubility in sc-CO2. The aim of this work is to compare different MS and to study alternative processes using pressurized CO2 for insoluble molecule in sc-CO2. By using high pressure reactor, DSC, HPLC and in vitro dissolution tests, the crystallinity and dissolution profiles of MS with different pore size (6.6 nm, 25.0 nm and 2.5 nm) impregnated with fenofibrate (FF) under sc-CO2 were compared to select the most appropriate carrier. Then, the selected MS has been impregnated under supercritical, subcritical and atmospheric conditions. We have shown that the MS pore size of 6.6 nm provides the higher amorphous drug loading capacity as well as the faster and higher drug dissolution. In addition, FF-MS formulations produced with pressurized CO2 as fusion medium, both in subcritical and supercritical conditions; give similar crystallinity and dissolution results compared to those produced with supercritical fluids as solvent. Through this study, we show new possibilities of using CO2 for insoluble compounds in this fluid. [less ▲]

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See detailMonocomponent non-isocyanate polyurethane adhesives based on a sol-gel process
Gomez-Lopez, Alvaro; Grignard, Bruno ULiege; Calvo, Iñigo et al

in ACS Applied Polymer Materials (2020), 2(5), 1839-1847

In the context of replacement of toxic conventional polyurethanes, non-isocyanates polyurethanes (NIPUs) based on 5-membered cyclic carbonates have emerged as the most promising alternatives. The low ... [more ▼]

In the context of replacement of toxic conventional polyurethanes, non-isocyanates polyurethanes (NIPUs) based on 5-membered cyclic carbonates have emerged as the most promising alternatives. The low reactivity of conventional 5-membered cyclic carbonates has limited the preparation of one pot-based systems due to long curing times. This work focuses in the improvement and application of these materials as adhesives by the combination of the NIPU chemistry with the sol-gel process able to cure in the presence of humidity. Thus, NIPU prepolymers are functionalized with (3-aminopropyl)triethoxysilane (APTES) and their curing behaviour as well as their adhesion performance are investigated by rheology and lap-shear test respectively. In spite of the ability of alkoxysilane to cure under ambient conditions, our results show that to have better adhesion properties, catalyst and temperature must be used to speed up the curing process. Hence, it is demonstrated that the fastest curing and the best performance are achieved at 100°C when acetic acid is employed as catalyst. Finally we demonstrate the importance of the soft (poly(propylene glycol) dicarbonate) to hard (resorcinol dicarbonate) ratio to achieve superior cohesion and adhesion properties in NIPUs adhesives. [less ▲]

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See detailThe coupling of CO2 with diols promoted by organic dual systems: Towards products divergence via benchmarking of the performance metrics
Brege, Antoine ULiege; Méreau, Raphaël; McGehee, K et al

in Journal of CO2 Utilization (2020), 38

Herein, we propose a critical study balancing two metal-free dual activating systems, namely DBU/EtBr and TEA/TsCl, for the coupling of CO2 with 1,x-diols to afford (a)cyclic carbonates. In-situ ATR-IR ... [more ▼]

Herein, we propose a critical study balancing two metal-free dual activating systems, namely DBU/EtBr and TEA/TsCl, for the coupling of CO2 with 1,x-diols to afford (a)cyclic carbonates. In-situ ATR-IR monitoring cor- related with DFT calculations led to mechanism propositions for the model formation of propylene carbonate from propylene glycol. Kinetics upon various experimental conditions were established for the first time, leading to an optimized synthetic protocol. The substrates scope was then investigated and selectivities toward the formation of cyclic or linear carbonates were correlated to the dual activating system and the diol structure. By choosing the suitable organic dual activating system, one is able to control the product selectivity to substituted ethylene- or trimethylene carbonate and/or acyclic compounds, providing a powerful tool to synthesize CO2- based precursors that are highly relevant for organic and polymer chemistry from ubiquitous building blocks. [less ▲]

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See detailInfluence of the cyclic vs. linear carbonate segments in the properties and performance of CO2-sourced polymer electrolytes for lithium batteries
Ouhib, Farid ULiege; Meabe, Leire; Mahmoud, Abdelfattah ULiege et al

in ACS Applied Polymer Materials (2020), 2(2), 922-931

Polycarbonates bearing linear carbonate linkages and polyether segments have demonstrated to be highly attractive solid electrolyte candidates for the design of safe energy storage devices, e.g. lithium ... [more ▼]

Polycarbonates bearing linear carbonate linkages and polyether segments have demonstrated to be highly attractive solid electrolyte candidates for the design of safe energy storage devices, e.g. lithium metal batteries. In this contribution, we are studying the influence of the introduction of some cyclic carbonate linkages within the polymer backbone on the electrolyte properties. We first describe the synthesis of polycarbonates/polyethers containing different contents of both linear and cyclic carbonate linkages within the chain by the copolymerization of a highly reactive CO2-based monomer (bis(-alkylidene cyclic carbonate)) with poly(ethylene glycol) diol and a dithiol at room temperature. We then explore the influence of the content of the cyclic carbonates and the loading of the polymer by lithium bis(trifluoromethane) sulfonimide (LiTFSI) on the electrolyte properties (glass transition and melting temperatures, ion conductivity and diffusivity). The best electrolyte candidate is characterized by a linear/cyclic carbonate linkage ratio of 82/18 when loaded with 30 wt% LiTFSI. It exhibits an ion conductivity of 5.6 10-5 S cm-1 at 25°C (7.9 10-4 S cm-1 at 60 °C), which surpasses by 150 % (424 % at 60 °C) the conductivity measured for a similar polymers bearing linear carbonate linkages only. It is also characterized by a high oxidation stability up to 5.6 V (vs. Li/Li+). A self-standing membrane is then constructed by impregnating a glass fiber filter by this optimal polymer, LiTFSI and a small amount of a plasticizer (tetraglyme). Cells are then assembled by sandwiching the membrane between a C-coated LiFePO4 (LFP) as the cathode and lithium as the anode and counter electrode. The cycling performances are evaluated at 0.1 C at 60 °C and room temperature for 40 cycles. Excellent cycling performances are noted with 100 % of the theoretical capacity (170 mAh g-1) at 60 °C, and 73.5 % of the theoretical capacity (125 mAh g-1) at 25 °C. [less ▲]

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See detailA catalytic domino approach towards oxo-alkyl carbonates and polycarbonates from CO2, propargylic alcohols and (mono- and di-) alcohols
Ngassam Tounzoua, Charlène ULiege; Grignard, Bruno ULiege; Brege, Antoine ULiege et al

in ACS Sustainable Chemistry and Engineering (2020)

We have explored the domino reaction between propargylic alcohols, carbon dioxide and various alcohols with the double objective to prepare oxo-alkylcarbonates with a high yield and selectivity under mild ... [more ▼]

We have explored the domino reaction between propargylic alcohols, carbon dioxide and various alcohols with the double objective to prepare oxo-alkylcarbonates with a high yield and selectivity under mild conditions and to extend the process to the synthesis of phosgene-free polycarbonates. We first searched for a common catalytic system that was highly selective for the two reactions involved in the domino process, i.e. the cycloaddition of CO2 to propargylic alcohol to yield α-alkylidene cyclic carbonate (αCC), and the alcoholysis of αCC to furnish the oxo-alkylcarbonate. Kinetics studies monitored by operando IR spectroscopy and supported by 1H-NMR analyses and DFT modeling have permitted to identify an efficient binary catalytic system composed of a combination of tetrabutylammonium phenolate [TBA][OPh] and silver iodide (AgI) (or copper iodide (CuI)) and to understand its action mode. The [TBA][OPh]/AgI catalytic system (5 mol%) was then successfully implemented for the selective preparation of a range of oxo-alkylcarbonates by the domino reaction with alcohols and propargylic alcohols of different structures. Most of these oxo-alkylcarbonates were produced at a high yield (≧ 97 %) under mild operating conditions, i.e. at 60 °C and 1 bar of CO2. The one-pot synthesis of various poly(β-oxocarbonate)s from bis(propargylic alcohol)s, diols and CO2 was finally investigated and the best operating conditions ([TBA][OPh]/AgI (10 mol%), 60 °C, 15 bar) afforded polycarbonate oligomers with weight-average molar masses of 4,300 g/mol. Although the system should be optimized to produce longer polymer chains, this process offers a new phosgene-free alternative to the synthesis of functional polycarbonates (poly(oxo-carbonate)s) under mild conditions. [less ▲]

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See detailPlein gaz : enjeux et perspectives de la valorisation du CO2
Léonard, Grégoire ULiege; Evrard, Brigitte ULiege; Grignard, Bruno ULiege et al

Conference given outside the academic context (2019)

Detailed reference viewed: 66 (17 ULiège)
See detailDual activation catalysts for the selective conversion of CO2 into alkylidene cyclic carbonates and oxoalkyl carbonates
Ngassam Tounzoua, Charlène ULiege; Grignard, Bruno ULiege; Jérôme, Christine ULiege et al

Conference (2019, September 24)

Carbon dioxide (CO2) is a greenhouse gas responsible for global warming. In the last decades, efforts have been put towards the valorization of this abundant, nontoxic inexhaustible C1 source for the ... [more ▼]

Carbon dioxide (CO2) is a greenhouse gas responsible for global warming. In the last decades, efforts have been put towards the valorization of this abundant, nontoxic inexhaustible C1 source for the synthesis of useful commodity chemicals. The synthesis of cyclic carbonates is attracting much interest due to its 100% atom efficiency reaction and its large potential scope for the design of complex organic molecules or novel functional polymers (polycarbonates, polyurethanes, etc.). 5-membered cyclic carbonates can be obtained by the coupling of CO2 with diols, epoxides and lastly, alkynols. The latter have the advantage of affording cyclic carbonates that are activated by the presence of an exocyclic vinylic bond, making them reactive towards alcohols and amines. In addition, their ring-opening is regio-selective affording β -oxo-carbonate by reaction with alcohols, β-oxo-urethanes with secondary amines or β-hydroxy-oxazolidones with primary amines. Due to the inertness and high thermodynamic stability of CO2, a catalyst is required to transform alkynols into alkylidene cyclic carbonates. Bases, ionic liquids), carbenes, metal salts, have been shown to promote the cyclisation of CO2 with alkynols. Although full conversions are obtained in certain cases, the selectivity remains an issue. Also, harsh conditions and/or excessive amounts of base are often used. In this work, we designed novel, cheap, highly efficient organocatalysts for the synthesis of α-alkylidene cyclic carbonates from CO2 and alkynols. Several organocatalysts, based on ammonium cations and basic anions were screened, and kinetic studies were performed by Raman spectroscopy to identify the best anion/cation couple. We further optimized our catalytic system by developing cooperative catalysts providing conditions for the selective formation of α-alkylidene cyclic carbonates and oxoalkylcarbonates under mild experimental conditions and short reaction times at low catalyst loading. [less ▲]

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See detailCO2-based monomers: a detailed investigation of the carbonation reaction over diols for the synthesis of (a)cyclic carbonates promoted by organic dual systems
Brege, Antoine ULiege; Méreau, Raphaël; Grignard, Bruno ULiege et al

Poster (2019, September 23)

The present research aims at investigating in details the reaction between carbon dioxide and a diol to afford cyclic and acyclic carbonates in moderate to good yields. Thanks to its chemical structure ... [more ▼]

The present research aims at investigating in details the reaction between carbon dioxide and a diol to afford cyclic and acyclic carbonates in moderate to good yields. Thanks to its chemical structure, CO2 has been identified as a promising reagent for the synthesis of organic carbonates as it is non-toxic, cheap and an abundant C1 renewable feedstock, and could potentially replace phosgene based carbonates produced industrially. Prior research has been focused on the epoxide/CO2 coupling to afford cyclic carbonates in good yields. Yet, this coupling suffers from limitations such as restricted substrates and exclusive synthesis of 5-membered cyclic carbonates. In order to extend the products availability through Carbon Dioxide Utilization, more recent research has been carried out with new substrates such as the use of diols. Thus, efforts are still needed to identify cheaper and more efficient protocols for the selective synthesis of cyclic and acyclic carbonates from the coupling of CO2 with diols. In this context, the use of organic bases/alkylating agent dual system as promoters and low pressure and temperature conditions (P<1MPa, r.t) seem to be a good alternative to afford organic carbonates. Thanks to an in-situ ATR-IR spectroscopy monitoring, a detailed understanding of the synthesis of propylene carbonate from propylene glycol and CO2 promoted by organic bases and the addition of co-reagents is proposed. Reaction intermediates are identified, and kinetic profiles determined for various parameters (pressure, temperature, solvent…). Two dual systems, one combining DBU and an alkyl halide (e.g Bromoethane), and another one with TEA and TsCl were compared. Different substrates were also tested such as 1,x diols (2 ≤ x ≤ 4) and Isosorbide. The selectivity toward the cyclic carbonate or the side products is discussed. Density Functional Theory (DFT) was also performed in this work to understand and validate the reaction pathways proposed via ATR-IR monitoring. Structures of transition states were optimized and comparisons between several reagents and/or paths were calculated, giving capital information about further enhancement of the CO2-diol conversion into carbonates. [less ▲]

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See detailOptimizing support properties of heterogeneous catalysts for the coupling of carbon dioxide with epoxides
Léonard, Géraldine L.-M.; Pirard, Sophie ULiege; Belet, Artium ULiege et al

in Chemical Engineering Journal (2019), 371

The study deals with the catalytic cyclocarbonation of epoxides to produce monomers used in the synthesis of polyurethane. A benchmark study of the textural properties of silica-based, doped or not ... [more ▼]

The study deals with the catalytic cyclocarbonation of epoxides to produce monomers used in the synthesis of polyurethane. A benchmark study of the textural properties of silica-based, doped or not, supports enabling the identification and optimization of the key parameters affecting the catalytic activity is reported. The results reveal that ammonium catalysts immobilized onto mesostructured supports with high surface area and low aggregation show better catalytic performances than analogue catalysts grafted onto microstuctured ones. While a high external surface area favours the grafting of ammonium salt, pore size must be large enough to enhance the accessibility of both carbon dioxide and epoxides to the catalytic sites. The activity of heterogeneous cat- alysts was evaluated for a model coupling reaction between carbon dioxide and propylene glycol diglycidylether. Using appropriated supports, cyclocarbonation yields are found to be higher in the presence of the hetero- geneous catalyst in comparison with the homogeneous one. These results allow to confirm the beneficial effect of the presence of residual OH silanol groups at the surface of the support, which activate epoxide through forming of hydrogen bonds. [less ▲]

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See detailAdvances in the use of CO2 as a renewable feedstock for the synthesis of polymers
Grignard, Bruno ULiege; Gennen, Sandro; Jérôme, Christine ULiege et al

in Chemical Society Reviews (2019), 48(16), 4466-4514

Carbon dioxide offers an accessible, cheap and renewable carbon feedstock for synthesis. Current interest in the area of carbon dioxide valorisation aims at new, emerging technologies that are able to ... [more ▼]

Carbon dioxide offers an accessible, cheap and renewable carbon feedstock for synthesis. Current interest in the area of carbon dioxide valorisation aims at new, emerging technologies that are able to provide new opportunities to turn a waste into value. Polymers are among the most widely produced chemicals in the world greatly affecting the quality of life. However, there are growing concerns about the lack of reuse of the majority of the consumer plastics and their after-life disposal resulting in an increasing demand for sustainable alternatives. New monomers and polymers that can address these issues are therefore warranted, and merging polymer synthesis with the recycling of carbon dioxide offers a tangible route to transition towards a circular economy. Here, an overview of the most relevant and recent approaches to CO2-based monomers and polymers are highlighted with particular emphasis on the transformation routes used and their involved manifolds. [less ▲]

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See detailA switchable domino process for the construction of novel CO2- sourced sulfur-containing building blocks and polymers
Ouhib, Farid ULiege; Grignard, Bruno ULiege; Van den Broeck, Elias et al

in Angewandte Chemie International Edition (2019), 58(34), 11768-11773

alpha-alkylidene cyclic carbonates (aCCs) recently emerged as attractive CO2-sourced synthons for the construction of complex organic molecules. Herein, we report the transformation of aCCs into novel ... [more ▼]

alpha-alkylidene cyclic carbonates (aCCs) recently emerged as attractive CO2-sourced synthons for the construction of complex organic molecules. Herein, we report the transformation of aCCs into novel families of sulfur-containing compounds by organocatalyzed chemoselective addition of thiols, following a domino process that is switched on/off depending on the desired product. The process is extremely fast, versatile in substrate scope, provides selectively linear thiocarbonates or elusive tetrasubstituted ethylene carbonates with high yields following a 100% atom economy reaction, and valorizes CO2 as a renewable feedstock. It is also exploited to produce a large diversity of unprecedented functional polymers. It constitutes a robust platform for the design of new sulfur-containing organic synthons and important families of polymers. [less ▲]

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See detailHeterogenization of a cyclocarbonation catalyst: optimization and kinetic study
Léonard, Géraldine L.-M.; Belet, Artium ULiege; Grignard, Bruno ULiege et al

in Catalysis Today (2019), 334

Different types of heterogeneous catalysts designed for a cyclocarbonation reaction between an epoxidized source and CO2 under supercritical conditions have been synthesized. The process implied a ... [more ▼]

Different types of heterogeneous catalysts designed for a cyclocarbonation reaction between an epoxidized source and CO2 under supercritical conditions have been synthesized. The process implied a quaternization step where a (haloalkyl)trimethoxysilane reacted with tributylamine leading to a tributyl(trimethoxysilylalkyl)ammonium halide, with iodine and bromine as halogens. Then, a grafting step onto commercial fumed silica through condensation reaction between the silane part and Si-OH surficial groups provided the immobilized catalyst. The efficiency of grafting has been validated by liquid 1H NMR, solid 29Si NMR and TG-DSC-MS analyzes. The benchmark cyclocarbonation reaction of polyethylene glycol diglycidylether at 80 °C and 100 bar during 4 h showed that the best immobilized catalyst was tributylpropylammonium iodide (IC3Q-EH5). It has also been shown that immobilization provided -surprisingly !- better conversions than the corresponding homogeneous catalyst’s: this phenomenon has been explained through an epoxide-ring-opening activating effect thanks to Si-OH surficial groups. Furthermore, kinetic studies performed by in situ Raman spectroscopy on IC3Q-EH5 showed that temperature had a strong influence on the yield of the reaction while CO2 pressure had only a small effect. Recycling of the catalyst has also been considered, but no precise conclusions could be conducted because of the high catalyst dispersion. Finally, the addition of a fluorinated alcohol co-catalyst allowed obtaining a similar yield but at 80 °C and 55 bar during only 2,5 h with the best candidate. [less ▲]

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See detailFast and facile one-pot one-step preparation of non-isocyanate polyurethane hydrogels in water at room temperature
Bourguignon, Maxime ULiege; Thomassin, Jean-Michel ULiege; Grignard, Bruno ULiege et al

in ACS Sustainable Chemistry and Engineering (2019), 7(14), 12601-12610

Since the discovery of polyurethanes (PU) by Otto Bayer in 1937, PU hydrogels are still commonly produced by the polyaddition of nasty and toxic polyisocyanates with polyols in organic solvents or in the ... [more ▼]

Since the discovery of polyurethanes (PU) by Otto Bayer in 1937, PU hydrogels are still commonly produced by the polyaddition of nasty and toxic polyisocyanates with polyols in organic solvents or in the bulk, followed by their swelling in water. Their direct one-pot one-step synthesis in water is not possible due to the fast hydrolysis of isocyanates. The attractive greener variant for PU that consists in the polyaddition of poly(5-membered cyclic carbonate)s with polyamines is also suffering for a similar drawback (the hydrolysis of the cyclic carbonates), but also for the low reactivity of the reagents at room temperature. Herein, we report the first synthesis of PU hydrogels by a non-isocyanate route in water at room temperature from easily accessible CO2-sourced 5-membered cyclic carbonates (5CCs) and a commercially available polyamine. We demonstrate that PU hydrogels are now formed with impressive short gel times (15-20 min) provided that the pH is adjusted in the 10.5-11.5 range in order to limit 5CCs hydrolysis. Hydrogels of good mechanical properties and high swelling ability are prepared in a facile one-pot process. The robustness of the process is also illustrated by dispersing clays (natural or synthetic) or a natural hydrosoluble polymer (gelatin) in the formulation. These additives do not perturb the polymerization and enable to modulate the mechanical properties of the hydrogel. This works opens enormous perspectives in the design of elusive PU-based materials in water from largely accessible 5- membered cyclic carbonates. [less ▲]

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See detailUpgrading CO₂ into novel families of regioregular and functional polymers
Grignard, Bruno ULiege; Gennen, Sandro; Ngassam Tounzoua, Charlène ULiege et al

Conference (2019, June 26)

Polycarbonates (PCs) and polyurethanes (PUs) belong to some of the world-leading polymers found in many of our daily life applications. PCs are mainly produced by polycondensation of alkylcarbonates ... [more ▼]

Polycarbonates (PCs) and polyurethanes (PUs) belong to some of the world-leading polymers found in many of our daily life applications. PCs are mainly produced by polycondensation of alkylcarbonates/phosgene derivatives with diols at high temperature, or by ring-opening polymerization of 5- or 6-membered cyclic carbonates while PUs are industrially made by polyaddition of diisocyanates with diols. Recent developments in the PUs field deal with the polyaddition of 5-membered dicyclic carbonates with diamines, but this polymerization is much slower compared to the isocyanate route and gave regio-irregular polymers of low molar mass due to the asence of selective ring-opening and the occurrence of side reactions. The polyaddition of dicyclic carbonates with diols would also be attractive to prepare PCs but is challenging due to the poor reactivity of the 5-membered cycles towards alcoholises. Until very recently, using a single 5-membered dicyclic carbonate platform to access various polymer families remained an elusive endeavour. In this talk, we will describe an innovative approach for the preparation of new families of PCs and PUs, by the facile room temperature polyaddition of novel activated CO2-sourced 5-membered biscyclic carbonates with diols (for PCs) or diamines (for PUs). These novel cyclic carbonates are prepared by organocatalyzed carboxylative coupling of CO2 with dialkynols. Although PCs require some organocatalyst to be produced, PUs synthesis do not require any activation. Moreover, this process allows for the synthesis of regioregular functional polymers free of defects and displaying high molar masses (Mn up to 100 kg/mol in some cases). The origin of this unprecedented reactivity will be explained as well as its impact on the polymer structure. We will also show that these novel CO2-sourced monomers can also be exploited to expand their scope of valorization to a fourth family of novel functional polymers, by tuning the nature of the comonomer. We believe that this platform of novel monomers is opening new perspectives in the facile production of novel and/or existing world-class relevant polymers by valorizing CO2 as a renewable feedstock. [less ▲]

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See detailInternational Conference on Carbon Dioxide Utilization (ICCDU)
Brege, Antoine ULiege; Méreau, Raphaël; Grignard, Bruno ULiege et al

Conference (2019, June 25)

The present research aims at investigating in details the reaction between carbon dioxide and a diol to afford cyclic and acyclic carbonates in moderate to good yields. Thanks to its chemical structure ... [more ▼]

The present research aims at investigating in details the reaction between carbon dioxide and a diol to afford cyclic and acyclic carbonates in moderate to good yields. Thanks to its chemical structure, CO2 has been identified as a promising reagent for the synthesis of organic carbonates as it is non-toxic, cheap and an abundant C1 renewable feedstock, and could potentially replace phosgene based carbonates produced industrially. Prior research has been focused on the epoxide/CO2 coupling to afford cyclic carbonates in good yields. Yet, this coupling suffers from limitations such as restricted substrates and exclusive synthesis of 5-membered cyclic carbonates. In order to extend the products availability through Carbon Dioxide Utilization, more recent research has been carried out with new substrates such as the use of diols. Although many different catalysts and reaction routes have already been investigated, efforts are still needed to identify cheaper and more efficient protocols for the selective synthesis of cyclic and acyclic carbonates from the coupling of CO2 with diols. In this context, the use of organic bases/alkylating agent dual system as promoters and low pressure and temperature conditions (P<1MPa, r.t) seem to be a good alternative to afford organic carbonates. The present work aims at providing, thanks to an in-situ ATR-IR spectroscopy monitoring, a detailed understanding of the synthesis of propylene carbonate from propylene glycol and CO2 promoted by DBU and the addition of alkyl halides. This analytical tool enabled to identify several reaction intermediates and to determine how the kinetic profiles, the reaction yields, and the selectivity of the reaction evolves with various parameters (pressure, temperature and nature of the base and alkyl halide). Thus, several experimental conditions have been tested as well as various alkyl halides in order to understand in details the effect on the selectivity and the efficiency of the reaction. Different substrates were also tested such as 1,x diols (2 ≤ x ≤ 4) and Isosorbide. The selectivity toward cyclic or biscarbonated compounds is discussed. Density Functional Theory (DFT) was also performed in this work to understand and validate the reaction pathways proposed via ATR-IR monitoring. Structures of transition states were optimized and comparisons between several reagents and/or paths were calculated, giving capital information about further enhancement of the CO2-diol conversion into carbonates. [less ▲]

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See detailCooperative catalysts for the selective synthesis of alkylidene cyclic carbonates from CO2 and propargylic alcohols
Ngassam Tounzoua, Charlène ULiege; Grignard, Bruno ULiege; Jérôme, Christine ULiege et al

Poster (2019, June)

Carbon dioxide (CO2) is a greenhouse gas responsible for global warming. In the last decades, efforts have been put towards the valorization of this abundant, nontoxic inexhaustible C1 source for the ... [more ▼]

Carbon dioxide (CO2) is a greenhouse gas responsible for global warming. In the last decades, efforts have been put towards the valorization of this abundant, nontoxic inexhaustible C1 source for the synthesis of useful commodity chemicals such as methanol, methane, carboxylic acids, urea, synthetic fuel and cyclic carbonates. Amongst those, the synthesis of cyclic carbonates is attracting much interest due to its 100% atom efficiency reaction and its large potential scope for the design of complex organic molecules or novel functional polymers (polycarbonates, polyurethanes, etc.). 5-membered cyclic carbonates can be obtained by the coupling of CO2 with diols, epoxides and lastly, alkynols. The latter have the advantage of affording cyclic carbonates that are activated by the presence of an exocyclic vinylic bond, making them reactive towards alcohols and amines. In addition, their ring-opening is regio-selective affording β-oxo-carbonate by reaction with alcohols, ß-oxo-urethanes with secondary amines or ß-hydroxy-oxazolidones with primary amines. Due to the inertness and high thermodynamic stability of CO2, a catalyst is required to transform alkynols into alkylidene cyclic carbonates. Bases, ionic liquids), carbenes, metal salts, have been shown to promote the cyclisation of CO2 with alkynols. Although full conversions are obtained in certain cases, the selectivity remains an issue. Also, harsh conditions and/or excessive amounts of base are often used. In this work, we designed novel, cheap, highly efficient organocatalysts for the synthesis of α-alkylidene cyclic carbonates from CO2 and alkynols. Several organocatalysts, based on ammonium cations and basic anions were screened, and kinetic studies were performed by Raman spectroscopy to identify the best anion/cation couple. We further optimized our catalytic system by developing cooperative catalysts providing conditions for the selective formation of α-alkylidene cyclic carbonates under mild experimental conditions and short reaction times at very low catalyst loading. [less ▲]

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See detailSynthesis of new PLGA based grafted polymers for formation of bioactive nanoparticles
Toullec, Clément; Boury, Frank; Grignard, Bruno ULiege et al

Poster (2019, May 27)

The loss of bone tissues because of age, obesity, trauma or diseases can provoke a significant morbidity and an important socio-economical cost. During the last few decades, tissue engineering and ... [more ▼]

The loss of bone tissues because of age, obesity, trauma or diseases can provoke a significant morbidity and an important socio-economical cost. During the last few decades, tissue engineering and regenerative medicine have become promising strategies for rebuilding bones. The tissue engineering of bones has for objective the functional regeneration of bones through a synergetic combination of biomaterial scaffolds, cells and active biomolecules such as proteins, peptides or growth factors. The objective of our work was to synthesize a copolymer, curdlan-graft-PLGA, in supercritical CO2 without any organic solvent. This copolymer was then used for the formulation of nanoparticles that are intended to be loaded with bioactive molecules for bone regeneration. Starting with cyclic monomers, glycolide and lactide, poly-lactic-co-glycolic acid (PLGA) was obtained through ring-opening polymerization (ROP) in supercritical carbon dioxide (scCO2). Curdlan (1,3-β-glucan), a polysaccharide, was used as an initiator. Organic catalysers, including 1,8-diazabicyclo[5.4.0]undec-7-ene and thio-urea, were also used. The purity, composition and molecular mass of the curdlan-graft-PLGA copolymer were determined with liquid NMR. Nanoparticles were prepared through a phase separation method. The copolymer was dissolved in dimethyl isosorbide (DMI), then an anti-solvent, an aqueous solution of glycine and NaOH, was progressively added in large excess. The average nanoparticle size was determined by dynamic light scattering. The morphology of nanoparticles was studied with scanning and transmission electronic microscopy. Finally, the zeta potential was also measured. In this work, we used curdlan both as an initiator for the ROP and as a backbone for the copolymerization with PLGA. Thus, the resulting curdlan-graft-PLGA copolymer is composed of PLGA chains grafted on the curdlan backbone. scCO2 is considered as a “green” solvent because its critical pressure and temperature are relatively low, it is abundant, inert, nontoxic and non-flammable. Therefore, the ROP in scCO2 allows to obtain the curdlan-graft-PLGA copolymer in one step without any toxic solvent. Moreover, the synthesis parameters were optimised to diminish the amount of organocatalysts used. The rate of conversion of this process was determined to be of 98% and the molar mass of the PLGA grafts synthesised of 10 000g.mol-1. Nanoparticles were formed using this copolymer via a method of nanoprecipitation by phase separation. This method uses the difference in hydrophilicity between PLGA and curdlan. Curdlan is more hydrophilic than PLGA, therefore it will be preferentially oriented toward the aqueous phase on the surface of the nanoparticles while the PLGA will find itself in the core. This configuration was confirmed by modifying the quantity of curdlan in the copolymer which leads to a difference in the zeta potential of nanoparticles. The particles were observed to be spherical with a diameter of 300 nm in average and a polydispersity index of 0.2. [less ▲]

Detailed reference viewed: 58 (1 ULiège)