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Bio-based building blocks and sustainable synthesis pathways were used to synthesise star-shaped polymers composed of a D-sorbitol core and polycaprolactone arms by ring opening polymerisation (ROP). The use of volatile organic solvents was avoided and less energy intense reaction conditions were achieved by performing the ROP in the bulk or in a green solvent, supercritical CO2 (scCO2). Two catalysts were tested: conventional tin(II) 2-ethylhexanoate (Sn(Oct)2) which is a Food and Drug Administration (FDA) approved metal catalyst and an enzyme, Novozym 435 (Lipase B from Candida Antarctica immobilised on a solid support). The influence of the reaction medium and of the nature of the catalyst on the molecular weight, the dispersity and the architecture of the PCL stars was investigated. The star polymers were characterised by 1H and 31P nuclear magnetic resonance (1H and 31P NMR) spectroscopy, size exclusion chromatography – multi-angle light scattering (SEC-MALS) and matrix-assisted laser desorption and ionisation-time of flight (MALDI-TOF) mass spectrometry. The use of scCO2 enabled the reduction of the reaction temperature of Sn(Oct)2 catalysed star D-sorbitol-polycaprolactone polymerisations from 140 to 95 °C. In addition, star polymers were successfully synthesised by enzyme catalysis in the bulk or in scCO2 at 60 °C; lower temperatures that could provide significant energy savings on a commercial scale. Thecatalyst was shown to have a pronounced influence on the architecture of the PCL stars. Regular star polymers were obtained in the presence of Sn(Oct)2 whereas Novozym 435 gave access to miktoarmtype star PCL. Finally, the influence of the number and length of the arms on the thermal properties of the star polymers was investigated by differential scanning calorimetry (DSC).

National audience; Le CO2 dense (liquide ou supercritique) constitue un solvant vert qui, en combinaison avec les polymères,permet d’explorer de nouveaux procédés et d’élaborer de nouveaux produits. Le CO2 dense plastifie lespolymères et solubilise les petites molécules, ce qui permet d’effectuer à plus faible température la mise enforme et la modification chimique des polymères et facilite la préparation de matériaux composites à partirde composés thermosensibles. Le CO2 dense est un non-solvant de la plupart des polymères. Il en résultela déclinaison de nombreux procédés hétérogènes en milieu CO2 dense. La conception de copolymèresCO2-solubles, amphiphiles CO2-phobes/CO2-philes et/ou fonctionnels permet de contrôler les phénomènesaux interfaces et d’assurer une stabilisation stérique des phases dispersées (émulsions, dispersions).Ceci ouvre la voie à de nombreux procédés propres en milieu CO2 dense, assistés par des polymèresCO2-solubles : synthèse de particules par polymérisation en dispersion, extraction, décontamination,imprégnation, fonctionnalisation de matériaux.

International audience; Double hydrophilic block copolymers (DHBC) in the presence of multivalent oppositely charged ions form polyion complexes (PIC) in the micellar form. We use PIC micelles as an ecofriendly structuring agents for templating ordered mesoporous materials [1,2] : after concomittant micellization and silica condensation, the porosity of the final material is revealed by simple elution in water and the polyions can be recycled in successive synthesis batches. Various mesoporous silica materials have been obtained from cubic to lamellar, although lyotropic behavior of PIC micelles on their own has seldom been reported if ever. Moreover, the control over the structure of the final material is not solely determined by the asymmetry ratio of the diblock copolymer : a single PIC system yields different mesostructured silica materials depending on the physico-chemical conditions. In an attempt to address the relation between the mesoporous material structure and the lyotropic behavior of these new templating agents, our attention was brought to the role of water which is actually a prominent constituent of PIC micelles.PIC micelles of PEO-b-PAA/oligoamines have been studied. The water content of the core of the micelles has been addressed by establishing the complete phase diagram of the polyelectrolyte complex PAA/oligoamine in its coacervate form. It amounts to 50%, varies non-monotonously with concentration and can be tuned by ionic strength, pH. Shape transition and phase transition are revealed by swelling laws of the correlation peak position obtained from X-ray scattering. From light scattering and osmometry we establish the equation of state  of a PEO-b-PAA/oligoamine electrostatic complex. Its lyotropic behavior is characterized by a transition of shape of the micelles at =0.16 and a transition to lamellar phase at =0.30 corresponding to various levels of deswelling of the corona and of the core.This study evidences the high compressibility of the core of the micelles as opposed to the core of amphiphilic copolymer micelles. This feature probably explains why lyotropic behavior of PIC micelles is less rich than the one of amphiphilic micelles. But it also brings versatility in the use of PIC micelles as templating agents for mesoporous materials.

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International audience; Upon pH stimulus, double hydrophilic block copolymers form polyion complexes (PIC) in the micellar form. We used PIC micelles as ecofriendly templates for the synthesis of ordered mesoporous materials. The porosity of the final material is revealed by simple inversion of the pH stimulus. Various mesoporous silica materials have been obtained from cubic to lamellar.The control over the structure of the final material is expected to relate to the lyotropic behavior just as observed when micelles of amphiphilic molecules are used as template. However such lyotropic behavior has never been reported for PIC micelles. Moreover the same PIC leads to different structured silica materials depending on the physico-chemical conditions.Using X-rays and light scattering, optical microscopy and osmometry, we establish the equation of state (osmotic pressure vs volume fraction) of a PEO-b-PAA/oligoamine electrostatic complex. Its lyotropic behavior is characterized by a transition of shape at 0.16 w/w and a transition to a lamellar phase at 0.30w/w. The water content of the core of the micelles is addressed from the complete phase diagram of the polyelectrolyte complex in its coacervate form and explains why a single complex leads to porous material of different structure.

International audience; A versatile and eco-compatible preparation route of functional ordered mesoporous materials will be described. It relies on the use of assemblies of hydrophilic diblock copolymers, in place of classical amphiphilic templates, as new structuring and functionalizing agents for the direct synthesis, at room temperature and in water, of polymer-functionalized mesoporous silica.The new structuring agents are dynamic PolyIon electrostatic Complex (PIC) micelles formed between double-hydrophilic-block-copolymers (DHBC) (constituted of a neutral block and an ionizable one) and an oppositely charged homopolyelectrolyte, which can be considered as an auxiliary of micellization of DHBC polymers.The different advantages of using PIC micelles are the following: due to their sensitivity to physicochemical parameters, PIC micelles allowed obtaining various hybrid mesostructures (cubic, 2D-hexagonal, lamellar...) by simply adjusting the material synthesis conditions using a unique DHBC/homopolyelectrolyte system. This is a consequence of the adjustable composition and water content of the polyion complex phase. The micellization process, which can be controlled by pH or ionic strength, is reversible in water and this allowed the recovery and recycling of the porogen polymers.Very interestingly, the use of PIC micelles permitted the direct preparation of polymer-functionalized mesopores. This was possible due to the easy dissociation of the polyion complex within the pores, selectively releasing the auxiliary of micellization while the DHBC remained for functionalizing the pores. This new method ensures an homogeneous functionalization of the mesopores, a control of the functional polymer chain lengths and a sufficient mesoporous volume. Moreover, the properties of the functional chains could be varied (acid, basic, metal-complexing...). Finally, this preparation route was extended to bio-functional hybrid mesophases useful as drug delivery systems [3] The direct formation of drug-loaded polymer-functionalized mesoporous materials was developed by using drug-polymer complex micelles as structuring agents ; this was shown with antibiotics exhibiting a pH-triggered release. Furthermore, studies are currently under way to estimate the catalytic performances of the new functional materials.

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communication orale O22; National audience

Polyion Complex (PIC) or Complex Coacervate Core (C3M) Micelles [1] have been used as structuring agents to template ordered mesostuctured porous silica materials [2]. PIC micelles assemble by electrostatic complexation of oppositely charged polyelectrolytes, one of them being a double hydrophilic block copolymer (DHBC). Compared to classical structuring agents obtained from amphiphilic molecules, PIC micelles offer several advantages: first, they can be recovered and reused in several mesoporous material synthesis cycles [2]. Secondly, they allow single step preparation of drug loaded porous materials [3]. Finally, tuning the characteristics of the porous material does no longer require the synthesis of new structuring agents: they can be adjusted by playing with the physico-chemical conditions, using a unique polyelectrolyte system. The present work aims at correlating the characteristics of the porous materials and the physico-chemical properties of the PIC micelles.Mesostructured materials have been prepared by condensation of TEOS in the presence of PIC micelles of polyethylene oxide-b-poly(acrylic acid) (POE-b-PAA) copolymer complexed with neomycin (NM) or oligochitosan (OC). TEM, sorption measurements and X-ray diffraction have shown that varying structures and pore sizes can be achieved by simply varying concentration and pH. On the other hand, using osmometry, specific ion potentiometry, elemental analysis and small angle X-ray scattering, the associative phase separation of poly(acrylic acid) in the presence of neomycin has been studied as a model system for the core of the PIC micelles.The hybrid materials obtained right after drying (without calcination) are porous. This is related to the high degree of swelling of the core of the PIC micelles that contains at least 50% of water in weight. The water content in the micelles varies with concentration because it is determined by osmotic equilibrium between the core and the suspending solution. This translates into variation of porous volume and allows fine tuning of the pore size in the hybrid material. These features are preserved after calcination. Finally, the pH of material synthesis has been shown to determine the drug loading: neomycin concentration in the hybrid porous material increases as pH increases.In conclusion, PIC micelles offer numerous advantages and opportunities in the domain of functional ordered mesostructured materials due to the sensitivity of their characteristics to physico-chemical parameters, allowing the reversibility of their assembling in water, the possible delivery of functional molecules and the possibility to control the swelling of PIC micelles core.References: [1] Voets, I. K.; de Keizer, A.; Stuart, M. A. C. Adv. Colloid Interface Sci., 2009, 147-48, 300-318.[2] Baccile, N.; Reboul, J.; Blanc, B.; Coq, B.; Lacroix-Desmazes, P.; In, M.; Gerardin, C. Angew. Chem. Int. Ed., 2008. 47(44), 8433-8437.[3] Molina, E.; Warnant, J.; Mathonnat, M.; Bathfield, M.; In, M.; Laurencin, D.; Jérôme, C.; Lacroix Desmazes, P.; Marcotte, N.; Gérardin, C. Langmuir, 2015. 31, 12839-12844.

Polyion Complex (PIC) or Complex Coacervate Core (C3M) Micelles [1] have been used as structuring agents to template ordered mesostuctured porous silica materials [2]. PIC micelles assemble by electrostatic complexation of oppositely charged polyelectrolytes, one of them being a double hydrophilic block copolymer (DHBC). Compared to classical structuring agents obtained from amphiphilic molecules, PIC micelles offer several advantages: first, they can be recovered and reused in several mesoporous material synthesis cycles [2]. Secondly, they allow single step preparation of drug loaded porous materials [3]. Finally, tuning the characteristics of the porous material does no longer require the synthesis of new structuring agents: they can be adjusted by playing with the physico-chemical conditions, using a unique polyelectrolyte system. The present work aims at correlating the characteristics of the porous materials and the physico-chemical properties of the PIC micelles.Mesostructured materials have been prepared by condensation of TEOS in the presence of PIC micelles of polyethylene oxide-b-poly(acrylic acid) (POE-b-PAA) copolymer complexed with neomycin (NM) or oligochitosan (OC). TEM, sorption measurements and X-ray diffraction have shown that varying structures and pore sizes can be achieved by simply varying concentration and pH. On the other hand, using osmometry, specific ion potentiometry, elemental analysis and small angle X-ray scattering, the associative phase separation of poly(acrylic acid) in the presence of neomycin has been studied as a model system for the core of the PIC micelles.The hybrid materials obtained right after drying (without calcination) are porous. This is related to the high degree of swelling of the core of the PIC micelles that contains at least 50% of water in weight. The water content in the micelles varies with concentration because it is determined by osmotic equilibrium between the core and the suspending solution. This translates into variation of porous volume and allows fine tuning of the pore size in the hybrid material. These features are preserved after calcination. Finally, the pH of material synthesis has been shown to determine the drug loading: neomycin concentration in the hybrid porous material increases as pH increases.In conclusion, PIC micelles offer numerous advantages and opportunities in the domain of functional ordered mesostructured materials due to the sensitivity of their characteristics to physico-chemical parameters, allowing the reversibility of their assembling in water, the possible delivery of functional molecules and the possibility to control the swelling of PIC micelles core.References: [1] Voets, I. K.; de Keizer, A.; Stuart, M. A. C. Adv. Colloid Interface Sci., 2009, 147-48, 300-318.[2] Baccile, N.; Reboul, J.; Blanc, B.; Coq, B.; Lacroix-Desmazes, P.; In, M.; Gerardin, C. Angew. Chem. Int. Ed., 2008. 47(44), 8433-8437.[3] Molina, E.; Warnant, J.; Mathonnat, M.; Bathfield, M.; In, M.; Laurencin, D.; Jérôme, C.; Lacroix Desmazes, P.; Marcotte, N.; Gérardin, C. Langmuir, 2015. 31, 12839-12844.

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