8 research outputs found
Catalyseurs organiques photolatents pour la polymérisation par ouverture de cycles différée
Photopolymerization is a growing process allowing preparing polymer materials, notably in the form of films or coatings. Nevertheless, it is mostly based on a radical polymerization mechanism that prevents obtaining fully biodegradable materials. The goal of this PhD work was thus to develop the photopolymerization of cyclic esters and carbonates by using two families of photobase generators (PBGs). First, already described PBGs, releasing cyclic amidine and guanidine-type superbases, were effectively employed to carry out the photopolymerization of L-LA and TMC in solution. Then, taking previous PBGs as models, we developed new PBGs able to release N-heterocyclic carbenes (NHCs) under UV irradiation. The release of NHCs from these âphotolatent NHCsâ was proven both by 1H NMR and by the formation of NHC.CS2 adducts. These PBGs also proved to be active for the ROP of L-LA and TMC in solution, but to a lesser extent than previous photobases. Indeed, slower kinetics of polymerization were observed, which was attributed to the presence of CO2 in the reaction medium (CO2 released by photodegradation of the PBG) that leads to the formation of NHC.CO2 adduct (inactive for ROP). Thus, the most efficient photobase (releasing TBD) was employed to carry out the bulk photopolymerizations of liquid cyclic esters (Δ-CL, ÎŽ-VL and even an innovative L-LA / TMC mixture). Finally, polymer networks have been formed by incorporating a bifunctional monomer into the reaction medium, allowing the preparation âon demandâ (temporal control) of potentially fully biodegradable materials in a one-pot process.La photopolymĂ©risation est un procĂ©dĂ© en plein essor qui permet dâaccĂ©der Ă des matĂ©riaux polymĂšres, notamment sous la forme de films ou de revĂȘtements. NĂ©anmoins, celle-ci est majoritairement basĂ©e sur un mĂ©canisme de polymĂ©risation radicalaire qui proscrit lâobtention de matĂ©riaux totalement biodĂ©gradables. Aussi, au cours de cette thĂšse, nous nous sommes intĂ©ressĂ©s Ă la photopolymĂ©risation par ouverture de cycle (photoROP) dâesters et de carbonates cycliques Ă lâaide de deux grandes familles de photogĂ©nĂ©rateurs de bases (PBGs). Tout dâabord, des PBGs, pouvant libĂ©rer des superbases de type amidine et guanidine cycliques ont Ă©tĂ© employĂ©es pour mener efficacement la photoROP du L-LA et du TMC en solution. Puis, nous nous sommes attachĂ©s Ă dĂ©velopper, sur le modĂšle des photobases prĂ©cĂ©dentes, de nouveaux PBGs qui libĂšrent sous irradiation UV des carbĂšnes N-hĂ©tĂ©rocycliques (NHCs). La libĂ©ration des NHCs Ă partir de ces « NHCs photolatents » a Ă©tĂ© prouvĂ©e par RMN 1H et par la formation dâadduits NHC.CS2. De mĂȘme, ces PBGs se sont rĂ©vĂ©lĂ©s actifs pour la photoROP du L-LA et du TMC en solution, mais avec une plus faible efficacitĂ© que les PBGs prĂ©cĂ©dents. En effet, les cinĂ©tiques de polymĂ©risation sont lentes du fait de la prĂ©sence de CO2 dans le milieu (libĂ©rĂ© lors de lâirradiation UV) qui conduit Ă la formation dâadduit NHC.CO2 inactif en ROP. Ainsi, la photobase la plus performante, libĂ©rant du TBD, a Ă©tĂ© employĂ©e afin dâeffectuer la photoROP en masse dâesters cycliques liquides (Δ-CL, ÎŽ-VL et un mĂ©lange innovant L-LA/TMC). Finalement, des rĂ©seaux ont Ă©tĂ© formĂ©s par incorporation dans le milieu rĂ©actionnel dâun monomĂšre bifonctionnel, permettant dâobtenir sur demande (contrĂŽle temporel) des matĂ©riaux rĂ©ticulĂ©s potentiellement entiĂšrement biodĂ©gradables
Catalyseurs organiques photolatents pour la polymérisation par ouverture de cycles différée
Photopolymerization is a growing process allowing preparing polymer materials, notably in the form of films or coatings. Nevertheless, it is mostly based on a radical polymerization mechanism that prevents obtaining fully biodegradable materials. The goal of this PhD work was thus to develop the photopolymerization of cyclic esters and carbonates by using two families of photobase generators (PBGs). First, already described PBGs, releasing cyclic amidine and guanidine-type superbases, were effectively employed to carry out the photopolymerization of L-LA and TMC in solution. Then, taking previous PBGs as models, we developed new PBGs able to release N-heterocyclic carbenes (NHCs) under UV irradiation. The release of NHCs from these âphotolatent NHCsâ was proven both by 1H NMR and by the formation of NHC.CS2 adducts. These PBGs also proved to be active for the ROP of L-LA and TMC in solution, but to a lesser extent than previous photobases. Indeed, slower kinetics of polymerization were observed, which was attributed to the presence of CO2 in the reaction medium (CO2 released by photodegradation of the PBG) that leads to the formation of NHC.CO2 adduct (inactive for ROP). Thus, the most efficient photobase (releasing TBD) was employed to carry out the bulk photopolymerizations of liquid cyclic esters (Δ-CL, ÎŽ-VL and even an innovative L-LA / TMC mixture). Finally, polymer networks have been formed by incorporating a bifunctional monomer into the reaction medium, allowing the preparation âon demandâ (temporal control) of potentially fully biodegradable materials in a one-pot process.La photopolymĂ©risation est un procĂ©dĂ© en plein essor qui permet dâaccĂ©der Ă des matĂ©riaux polymĂšres, notamment sous la forme de films ou de revĂȘtements. NĂ©anmoins, celle-ci est majoritairement basĂ©e sur un mĂ©canisme de polymĂ©risation radicalaire qui proscrit lâobtention de matĂ©riaux totalement biodĂ©gradables. Aussi, au cours de cette thĂšse, nous nous sommes intĂ©ressĂ©s Ă la photopolymĂ©risation par ouverture de cycle (photoROP) dâesters et de carbonates cycliques Ă lâaide de deux grandes familles de photogĂ©nĂ©rateurs de bases (PBGs). Tout dâabord, des PBGs, pouvant libĂ©rer des superbases de type amidine et guanidine cycliques ont Ă©tĂ© employĂ©es pour mener efficacement la photoROP du L-LA et du TMC en solution. Puis, nous nous sommes attachĂ©s Ă dĂ©velopper, sur le modĂšle des photobases prĂ©cĂ©dentes, de nouveaux PBGs qui libĂšrent sous irradiation UV des carbĂšnes N-hĂ©tĂ©rocycliques (NHCs). La libĂ©ration des NHCs Ă partir de ces « NHCs photolatents » a Ă©tĂ© prouvĂ©e par RMN 1H et par la formation dâadduits NHC.CS2. De mĂȘme, ces PBGs se sont rĂ©vĂ©lĂ©s actifs pour la photoROP du L-LA et du TMC en solution, mais avec une plus faible efficacitĂ© que les PBGs prĂ©cĂ©dents. En effet, les cinĂ©tiques de polymĂ©risation sont lentes du fait de la prĂ©sence de CO2 dans le milieu (libĂ©rĂ© lors de lâirradiation UV) qui conduit Ă la formation dâadduit NHC.CO2 inactif en ROP. Ainsi, la photobase la plus performante, libĂ©rant du TBD, a Ă©tĂ© employĂ©e afin dâeffectuer la photoROP en masse dâesters cycliques liquides (Δ-CL, ÎŽ-VL et un mĂ©lange innovant L-LA/TMC). Finalement, des rĂ©seaux ont Ă©tĂ© formĂ©s par incorporation dans le milieu rĂ©actionnel dâun monomĂšre bifonctionnel, permettant dâobtenir sur demande (contrĂŽle temporel) des matĂ©riaux rĂ©ticulĂ©s potentiellement entiĂšrement biodĂ©gradables
Photolatent organocatalysts for delayed ring-opening polymerization
La photopolymĂ©risation est un procĂ©dĂ© en plein essor qui permet dâaccĂ©der Ă des matĂ©riaux polymĂšres, notamment sous la forme de films ou de revĂȘtements. NĂ©anmoins, celle-ci est majoritairement basĂ©e sur un mĂ©canisme de polymĂ©risation radicalaire qui proscrit lâobtention de matĂ©riaux totalement biodĂ©gradables. Aussi, au cours de cette thĂšse, nous nous sommes intĂ©ressĂ©s Ă la photopolymĂ©risation par ouverture de cycle (photoROP) dâesters et de carbonates cycliques Ă lâaide de deux grandes familles de photogĂ©nĂ©rateurs de bases (PBGs). Tout dâabord, des PBGs, pouvant libĂ©rer des superbases de type amidine et guanidine cycliques ont Ă©tĂ© employĂ©es pour mener efficacement la photoROP du L-LA et du TMC en solution. Puis, nous nous sommes attachĂ©s Ă dĂ©velopper, sur le modĂšle des photobases prĂ©cĂ©dentes, de nouveaux PBGs qui libĂšrent sous irradiation UV des carbĂšnes N-hĂ©tĂ©rocycliques (NHCs). La libĂ©ration des NHCs Ă partir de ces « NHCs photolatents » a Ă©tĂ© prouvĂ©e par RMN 1H et par la formation dâadduits NHC.CS2. De mĂȘme, ces PBGs se sont rĂ©vĂ©lĂ©s actifs pour la photoROP du L-LA et du TMC en solution, mais avec une plus faible efficacitĂ© que les PBGs prĂ©cĂ©dents. En effet, les cinĂ©tiques de polymĂ©risation sont lentes du fait de la prĂ©sence de CO2 dans le milieu (libĂ©rĂ© lors de lâirradiation UV) qui conduit Ă la formation dâadduit NHC.CO2 inactif en ROP. Ainsi, la photobase la plus performante, libĂ©rant du TBD, a Ă©tĂ© employĂ©e afin dâeffectuer la photoROP en masse dâesters cycliques liquides (Δ-CL, ÎŽ-VL et un mĂ©lange innovant L-LA/TMC). Finalement, des rĂ©seaux ont Ă©tĂ© formĂ©s par incorporation dans le milieu rĂ©actionnel dâun monomĂšre bifonctionnel, permettant dâobtenir sur demande (contrĂŽle temporel) des matĂ©riaux rĂ©ticulĂ©s potentiellement entiĂšrement biodĂ©gradables.Photopolymerization is a growing process allowing preparing polymer materials, notably in the form of films or coatings. Nevertheless, it is mostly based on a radical polymerization mechanism that prevents obtaining fully biodegradable materials. The goal of this PhD work was thus to develop the photopolymerization of cyclic esters and carbonates by using two families of photobase generators (PBGs). First, already described PBGs, releasing cyclic amidine and guanidine-type superbases, were effectively employed to carry out the photopolymerization of L-LA and TMC in solution. Then, taking previous PBGs as models, we developed new PBGs able to release N-heterocyclic carbenes (NHCs) under UV irradiation. The release of NHCs from these âphotolatent NHCsâ was proven both by 1H NMR and by the formation of NHC.CS2 adducts. These PBGs also proved to be active for the ROP of L-LA and TMC in solution, but to a lesser extent than previous photobases. Indeed, slower kinetics of polymerization were observed, which was attributed to the presence of CO2 in the reaction medium (CO2 released by photodegradation of the PBG) that leads to the formation of NHC.CO2 adduct (inactive for ROP). Thus, the most efficient photobase (releasing TBD) was employed to carry out the bulk photopolymerizations of liquid cyclic esters (Δ-CL, ÎŽ-VL and even an innovative L-LA / TMC mixture). Finally, polymer networks have been formed by incorporating a bifunctional monomer into the reaction medium, allowing the preparation âon demandâ (temporal control) of potentially fully biodegradable materials in a one-pot process
UV-Initiated Ring Opening Polymerization of l -Lactide Using a Photobase Generator
International audienc
Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
International audienc
In Situ Generated RutheniumâArene Catalyst for Photoactivated Ring-Opening Metathesis Polymerization through Photolatent N-Heterocyclic Carbene Ligand
1,3-Bis(mesityl)imidazolium tetraphenylborate (IMesH+ BPh4â) can be synthesized in one step by anion metathesis between the corresponding imidazolium chloride and sodium tetraphenylborate. In the presence of 2-isopropylthioxanthone (sensitizer), an IMes N-heterocyclic carbene (NHC) ligand can be photogenerated under irradiation at 365â
nm through coupled electron/proton transfer reactions. By combining this tandem NHC photogenerator system with metathesis inactive [RuCl2(p-cymene)]2 precatalyst, the highly active RuCl2(p-cymene)(IMes) complex can be formed in situ, enabling a complete ring-opening metathesis polymerization (ROMP) of norbornene in the matter of minutes at room temperature. To the best of our knowledge, this is the first example of a photogenerated NHC. Its exploitation in photoROMP has resulted in a simplified process compared to current photocatalysts, because only stable commercial or easily synthesized reagents are required.Photolatent N-heterocyclic Carbenes for Delayed Ring Opening Polymerizatio
Exploring the cellular uptake and localisation of phosphorescent rhenium fac-tricarbonyl metallosurfactants as a function of lipophilicity
A systematic study of the cellular uptake of emissive complexes as a function of their lipophilicity is presented. Here a series of amphiphilic rhenium fac-tricarbonyl bisimine complexes bearing axial substituted imidazole or thiazole ligands, [Re(bpy)(CO)3(ImCnHm)]+ {n = 1 m = 3 (1+), n = 4 m = 9 (2+), n = 8 m = 17 (3+), n = 12 m = 25 (4+), n = 16 m = 33 (5+), n = 2 m = 3 (6+); bpy = 2,2'-bipyridine, Im = imidazole} and [Re(bpy)(CO)3(L)]+ {L = 1-mesitylimidazole, ImMes (7+), 4,5-dimethylthiazole, dmt (8+) and 4-methyl-5-thiazole-ethanol, mte (9+)} is reported. The X-ray crystal structures of 2+, 8+ and 9+ confirm the geometry and expected distribution of ligands and indicated that the plane of the imidazole/thiazole ring is approximately parallel to the long axis of the bipy ligand. Luminescence studies revealed excellent properties for their use in cell imaging with visible excitation and broad emission profiles. Their uptake in two distinct species has been examined by fluorescence imaging of the diplomonad fish parasite Spironucleus vortens (S. vortens) and rod-shaped yeast Schizosaccharomyces pombe (Schiz. pombe) as a function of their lipophilicity. The uptake of the complexes was highest for the more lipophilic 2+-5+ in both S. vortens and Schiz. pombe in which the long alkyl chain aids in crossing bilipid membranes. However, the increased lipophilicity of longer chains also resulted in greater toxicity. Localisation over the whole cell varied with differing alkyl chain lengths with complex 2+ preferentially locating to the nucleus of S. vortens, 3+ showing enhanced nuclear partitioning in Schiz. pombe, and 4+ for the remaining cell wall bound in the case of S. vortens. Interestingly, complexes of intermediate lipophilicity such as 7+ and 8+ showed reasonable uptake, proved to be non-toxic, and were capable of crossing exterior cell walls and localising in the organelles of the cells.</p