Syndioselective ring-opening polymerization and copolymerization of trans-1,4-cyclohexadiene carbonate mediated by achiral metal- and organo-catalysts

International audienceThe ring-opening polymerization (ROP) of trans-1,4-cyclohexadiene carbonate (CHDC) has been investigated computationally and experimentally. DFT computations indicate that ring-opening of CHDC is thermodynamically possible, yet to a lesser extent than that of trans-cyclohexene carbonate (CHC). Effective homopolymerizations of rac-CHDC and simultaneous or sequential copolymerizations of rac-CHDC with rac-CHC and L-LA were achieved with a diaminophenolate zinc-based complex ([(NNO)ZnEt]) or a guanidine (TBD) associated with an alcohol. These ROP reactions, which confirmed the lower reactivity of rac-CHDC vs. rac-CHC, especially in homopolymerization, proceeded without any decarboxylation. Quite uniquely, highly syndiotactic PCHDC was obtained from ROP of rac-CHDC with both the zinc- and TBD-based catalysts, as revealed by 13C{1H} NMR studies. The prepared homopolymers and block or random copolymers were characterized by 1H, 13C{1H} NMR, MALDI-ToF MS, SEC and DSC techniques

Nanomatériaux métalliques et organométalliques pour l’électronique moléculaire, la reconnaissance et la catalyse

La synthèse et la caractérisation de la structure électronique de nanosystèmes contenant des complexes redox en forme d'étoile ou dendritiques ont été conduites en vue d'applications dans le domaine des matériaux et de la catalyse. La première partie est consacrée à la description de ces nanomatériaux, la seconde partie à la synthèse et aux propriétés de nanoparticules métalliques pour des applications biomédicales et catalytiques, et la troisième partie à la mise en œuvre et optimisation des propriétés catalytique de nanoréacteurs moléculaires et nanoparticulaires. Ces nanoréacteurs catalytiques se sont montrés particulièrement efficaces pour des réactions de métathèse oléfiniques et pour des réactions de couplage carbone-carbone de type Miyaura-Suzuki. Les réactions catalytiques ont pu être conduites dans l'eau avec des quantités extrêmement faibles de catalyseur. Dans ce dernier cas, le caractère « homéopathique » des catalyseurs a même pu être démontré.Synthesis and characterization of the electronic structures of star-shape and dendritic and nanoparticle-centered nanosystems containing redox-active groups have been carried out for applications in materials chemistry and catalysis. The first part of the manuscript describes molecular nanomaterials, the second part nanoparticles for catalytic and biomedical applications, and the third part catalytic processes optimized in nanoreactors of molecular or nanoparticle types. The catalytic nanoreactors have been shown to be extremely efficient for olefin metathesis reactions and for Miyaura-Suzuki reactions. Catalytic reactions could be performed in water using extremely low amounts of nanoreactor-stabilized catalysts. In the latter example, catalysis is even « homeopathic »

Nanomatériaux métalliques et organométalliques pour l’électronique moléculaire, la reconnaissance et la catalyse

La synthèse et la caractérisation de la structure électronique de nanosystèmes contenant des complexes redox en forme d'étoile ou dendritiques ont été conduites en vue d'applications dans le domaine des matériaux et de la catalyse. La première partie est consacrée à la description de ces nanomatériaux, la seconde partie à la synthèse et aux propriétés de nanoparticules métalliques pour des applications biomédicales et catalytiques, et la troisième partie à la mise en œuvre et optimisation des propriétés catalytique de nanoréacteurs moléculaires et nanoparticulaires. Ces nanoréacteurs catalytiques se sont montrés particulièrement efficaces pour des réactions de métathèse oléfiniques et pour des réactions de couplage carbone-carbone de type Miyaura-Suzuki. Les réactions catalytiques ont pu être conduites dans l'eau avec des quantités extrêmement faibles de catalyseur. Dans ce dernier cas, le caractère « homéopathique » des catalyseurs a même pu être démontré.Synthesis and characterization of the electronic structures of star-shape and dendritic and nanoparticle-centered nanosystems containing redox-active groups have been carried out for applications in materials chemistry and catalysis. The first part of the manuscript describes molecular nanomaterials, the second part nanoparticles for catalytic and biomedical applications, and the third part catalytic processes optimized in nanoreactors of molecular or nanoparticle types. The catalytic nanoreactors have been shown to be extremely efficient for olefin metathesis reactions and for Miyaura-Suzuki reactions. Catalytic reactions could be performed in water using extremely low amounts of nanoreactor-stabilized catalysts. In the latter example, catalysis is even « homeopathic »

Block and Random Copolymers of 1,2-Cyclohexyl Cyclocarbonate and L-Lactide or Trimethylene Carbonate Synthesized by Ring-Opening Polymerization

International audienceThe sequential and random ring-opening polymns. (ROP) of racemic-trans-cyclohexene carbonate (rac-CHC) or enantiopure trans-(R,R)-cyclohexene carbonate ((R,R)-CHC) with L-lactide (LLA) or trimethylene carbonate (TMC) have been performed. Catalytic systems based on zinc diaminophenolate [(NNO)ZnEt] ((NNO)- = 2,4-di-tert-butyl-6-\[(2'-dimethylaminoethyl)methylamino]methyl\phenolate)) or tris[N,N-bis(trimethysilyl)amide]yttrium (Y[N(SiMe3)2]3) complexes, or a guanidine-type organocatalyst (1,5,7-triazabicyclo[4.4.0]dec-5-ene, TBD), combined to an alc. (BnOH or iPrOH) as initiator/chain-transfer agent were used. Well-defined diblock P(rac-CHC)-b-PLLA and P((R,R)-CHC)-b-PLLA and random P(rac-CHC)-co-PLLA and P(rac-CHC)-co-PTMC copolymers were thus synthesized with molar mass values up to Mn,NMR = ca. 34 000 g mol-1 and rather narrow dispersity values (DM = 1.2-1.7). 1H and 13C\1H\ NMR characterizations of the copolymers revealed the presence of -OBn or -OiPr chain-end groups, thereby supporting the active role of exogenous alc. as initiator. No decarboxylation reaction was ever obsd. during any copolymn., thus providing PCHC/PLLA and PCHC/PTMC copolymers void of ether defects. Thermal anal. of the copolymers assessed by DSC and TGA confirmed their block or random structure. The block PCHC-b-PLA and the random PCHC-co-PLLA and PCHC-co-PTMC copolymers represent the first examples of such copolymers synthesized by ring-opening copolymn. of the two comonomers. The latter PCHC-co-PTMC copolymers randomly combining CHC and TMC units are the first examples ever reporte

α-Trialkoxysilyl Functionalized Polycyclooctenes Synthesized by Chain-Transfer Ring-Opening Metathesis Polymerization

International audienceRing-opening metathesis polymn./cross-metathesis (ROMP/CM) of cyclooctene (COE) or 3-alkyl-substituted COEs (3R-COEs, R = Et, n-hexyl) using several trialkoxysilyl monofunctionalized alkenes as chain-transfer agents (CTAs; vinyl trimethoxysilane (1), allyl trimethoxysilane (2), and 3-(trimethoxysilyl)propyl acrylate (3)) and various Ru-carbene-alkylidene catalysts afforded several trialkoxysilyl mono- and difunctionalized polyolefins. The formation of α-monofunctional (MF), α,ω-difunctional (DF), isomerized α-monofunctional (IMF), linear nonfunctional (LNF), isomerized linear nonfunctional (ILNF), and cyclic nonfunctional (CNF) PCOEs is rationalized by a two-stage mechanism. First, formation of monofunctionalized (MF) and nonfunctionalized (LNF, CNF) macromols. takes place through a ROMP/CM along with RCM (ring-closing metathesis) process. Subsequently, C=C isomerization (ISOM) combined with a second CM process give isomerized (ILNF, IMF) and difunctionalized (DF) macromols. The nonfunctionalized polymers (CNF, LNF, and ILNF) were formed in minor quantities compared to the trialkoxysilyl-functionalized polymers (MF, IMF, and DF), as evidenced by NMR and MALDI-ToF MS analyses and fractionation expts. The rate and selectivity of the reaction varied with the nature of the CTA, COE substituent, catalyst, and to a lesser extent of the solvent. The use of 1,4-benzoquinone (BZQ) as additive allowed inhibiting completely the ISOM process. Alternatively, steric hindrance in 3-RCOEs substituted monomers resulted in an ISOM-free process with selective formation of MF polymers. The reactive Grubbs' second-generation catalyst (G2) afforded the best compromise in terms of productivity, reactivity, and selectivity. Under optimized conditions favoring the formation of MF/DF, i.e., in CH2Cl2 at 40 °C for 24 h with [COE]0/[CTA 3]0/[G2]0/[BZQ]0 = 2000:20-200:1:100, the polymn. was rather well-controlled. While CTAs 1 and 3 selectively gave mixts. of MF and DF, allyl CTA 2 resulted in a mixt. of IMF, MF, and DF

Enantiopure Isotactic PCHC Synthesized by Ring-Opening Polymerization of Cyclohexene Carbonate

International audienceThe ring-opening polymerization (ROP) of racemic trans-cyclohexene carbonate (rac-CHC) and enantiopure trans-(R,R)-CHC is successfully carried out with various catalyst systems. Poly(cyclohexene carbonate) (PCHC) with a slight isotactic bias (Pm = ca. 60–76%) is obtained by ROP of rac-CHC catalyzed by zinc diaminophenolate, zinc β-diketiminate, yttrium bis(phenolate), or 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in combination with an alcohol as a co-initiator. Purely isotactic PCHC is synthesized for the first time via ROP of enantiopure (R,R)-CHC with a zinc/benzyl alcohol catalyst system. All reactions proceed without decarboxylation, affording well-defined PCHCs with Mn,NMR up to 17 000 g mol–1 and ĐM = ca. 1.2. Purely isotactic PCHC is semicrystalline, with Tg = 130 °C, Tc = 162 °C, and Tm = 248 °C. DFT computations further highlight the significant favorable impact of the trans-cyclohexane ring-strain to enable the ROP of CHC, as opposed to meso-CHC which is unreactive