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Block copolymers based on ethylene (E) and butadiene (B) were prepared using the ansa-bis(fluorenyl) complex {Me

International audience; A one-pot synthesis method for various α-vinyl,ω-methoxysilyl polyethylene oligomers with well-defined lengths and high end-group functionalities and crystallinities is presented. This method relies on the combination of catalyzed chain growth of ethylene in the presence of a di(alkenyl)magnesium chain transfer agent and a neodymocene complex, followed by efficient deactivation using a variety of silane reagents: trimethoxymethylsilane, trimethoxyvinylsilane and tetramethoxysilane. Further condensation of the ω-methoxysilyl groups of these polymers in active medium (toluene/acetic acid mixture) leads to complex architectures such as comb-like structures or star-like structures that combine high vinyl functionality at extremities with a high crystallinity.

International audience; A range of dialkenylmagnesium compounds ([CH2═CH(CH2)n]2Mg; n = 1–6) were synthesized and used as chain transfer agents (CTA) with either (C5Me5)2NdCl2Li(OEt2)2 (1) or [Me2Si(C13H8)2Nd(BH4)2Li(thf)]2 (2) neodymium precursors for the polymerization of ethylene. In all cases, the systems followed a controlled coordinative chain transfer polymerization mechanism. The intramolecular insertion of the vinyl group on the CTA in growing chains is possible and led to the formation of cyclopentyl, cyclohexyl, and possibly cycloheptyl chain ends. While the production of cyclopentyl- or cyclohexyl-capped polyethylene chains can be quantitative (n = 2–5), the integrity of this double bond can also be kept if n is higher than 6. In comparison to 1/CTA catalytic systems, 2/CTA catalytic systems showed a higher propensity to produce cycloalkyl chain ends. This was ascribed to the lower steric demand around the active site, as shown by DFT calculations. In addition, the formation of bis(cyclopentylmethyl)magnesium from dipentenylmagnesium using a catalytic amount of 2 was shown.

International audience; The synthesis and characterization of silica-grafted monopodal and bipodal aluminum hydrides has been achieved starting from 200 °C- and 700 °C-annealed silica and [AlH3(NMe2Et)]. The mechanism by which aluminum trishydride reacts with isolated and vicinal silanols, assisted by the amine, has been investigated computationally at the ωB97XD-DFT level.

Leaching of (n-BuCp)2ZrCl2/MAO catalyst from silica supports has been studied in slurry phase ethylene homopolymerisation by changing i) the polymerization protocol, ii) aluminum alkyl scavengers and iii) by adding butylated hydroxytoluene (BHT-H) along with aluminum alkyl scavengers. The impact of these three variations on the ethylene polymerization kinetics of the said metallocene/MAO/silica catalyst is also analyzed. The obtained results show that (n-BuCp)2ZrCl2/MAO does not leach from the silica support if pre-contact between the heterogeneous catalyst and aluminum alkyl scavenger is avoided. Furthermore, the addition of equimolar amounts of BHT-H and triisobutylaluminum (TIBA) into the reaction milieu generates Al(i-Bu)BHT2 which appears to be a non-interacting scavenger leading to no catalyst leaching (and therefore, no reactor fouling). This observation has been made by pre-contacting and avoiding the pre-contact between the silica supported (n-BuCp)2ZrCl2/MAO catalyst and the reaction mixture containing equimolar amounts of BHT-H and TIBA followed by the analysis of reactor conditions as well as the obtained polyethylene morphology. Molecular and physical properties of HDPE remain very similar by changing the polymerization protocol or the aluminum alkyl scavenger or by using BHT-H.

The multistep synthesis of a polyethylene-supported iridium(III)-(N-heterocyclic carbene) hydrogen/deuterium exchange catalyst was performed starting from an iodo-polyethylene obtained via catalyzed polyethylene chain growth (CCG) on magnesium. Unique thermomorphic polyethylene properties give the possibility to perform catalytic hydrogen/deuterium exchange reactions at 100 °C in the homogeneous phase with simple catalyst separation as a precipitate at room temperature. The catalytic activity of the polymer-supported catalyst was compared with that of its monomeric analogue. The catalytic studies showed that the supported catalyst exhibits similar profiles and turnover numbers as homogeneous counterparts without deactivation.

Summary A range of crystalline copolymers of ethylene with α-olefins (propene, hexene, octene and octadecene) were prepared using the complexes Et(Ind)2ZrCl2 and (nBuCp)2ZrCl2 activated with MAO. The average composition of the copolymers was measured using 1H- and 13C-NMR. Then the samples were characterized by High Temperature SEC and DSC. These investigations showed that polymers are homogeneous in composition and consequently were suitable to be used as standards for TREF. This work provided calibrations curves for TREF that can be used on a wide range of α-olefin contents. Finally, these calibrations curves were used to characterize heterogeneous copolymers of ethylene/hexene synthesized using a conventional Ziegler-Natta catalyst.

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Copolyamides of PA 66/6 lithium 5-sulfoisophthalic acid (LiSIPA) containing up to 40 mol % of LiSIPA were prepared in a 1L-pilot reactor operating at high pressures and high temperatures. Interestingly, the presence of lithium sulfonate moieties highly impacted the glass transition temperature of the polyamide. The Tg increased from 59 °C for PA 66 to 155 °C for a copolymer containing about 40 mol % of LiSIPA. 1,3-Dihexylbenzenedicarboxamide and lithium p-toluenesulfonate were synthesized as model compounds to investigate the interaction of lithium sulfonate moieties and amide functions. Infrared spectroscopy using ATR technology performed on mixture of both compounds showed that the carbonyl group of amide functions interacts with the lithium cation of lithium sulfonate moieties. Similar SO and CO adsorption bands were observed in copolyamides PA 66/6LiSIPA and in mixture of model compounds, which strongly suggest the formation in the copolyamides of physical cross-linking points centered on lithium cations coordinated by carbonyl groups of amide functions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

In the current contribution it is demonstrated - for the first time - that poly(ethylene) (M(n) = 1,400 as well as 2,800 g · mol(-1) , PDI = 1.2) can be readily equipped with highly reactive cyclopentadienyl (Cp) end groups. The Cp terminal poly(ethylene) can subsequently be reacted in an efficient hetero Diels-Alder (HDA) reaction with macromolecules (poly(isobornyl acrylate) (M(n) = 4,600 g · mol(-1) , PDI = 1.10) and poly(styrene) (M(n) = 6,300 g · mol(-1) , PDI = 1.13) featuring strongly electron withdrawing thiocarbonyl thio end groups, prepared via reversible addition fragmentation chain transfer (RAFT) polymerization employing benzylpyridin-2-yldithioformate (BPDF) as transfer agent. The resulting block copolymers have been analyzed via high-temperature size exclusion chromatography (SEC) as well as nuclear magnetic resonance (NMR) spectroscopy. The current system allows for the removal of the excess of the non-poly(ethylene) containing segment via filtration of the poly(ethylene)-containing block copolymer. However, the reaction temperatures need to be judiciously selected. Characterization of the generated block copolymers at elevated temperatures can lead - depending on the block copolymer type - to the occurrence of retro Diels-Alder processes. The present study thus demonstrates that RAFT-HDA ligation can be effectively employed for the generation of block copolymers containing poly(ethylene) segments.

Polyethylene (PE), alkoxyamine- and thiol-terminated PEs (PE-TEMPO and PE-SH, respectively) can be converted to macroradicals using a peroxide, a thermal cleavage of the alkoxyamine and a hydrogen transfer reaction of the thiol, respectively. The addition of these macroradicals to multiwalled carbon nanotubes (MWCNTs) were compared by performing grafting reactions at 160 degrees C in 1,3-dichlorobenzene as solvent. Raman spectroscopy was utilized to follow the introduction of PE on the MWCNTs' surface while thermogravimetric and elemental analysis indicated the extent of this grafting. The grafting ratio was found to be in the range of 19-36 wt %. PE-functionalized MWCNTs were imaged by transmission elec-tronic microscopy showing a PE layer with various thicknesses covering the surface of nanotubes. It was found that higher levels of grafting were obtained using PE-2,2,6,6-tetramethyl-piperidinyl-1-oxy and PE-SH rather than a radical grafting reaction in which dicumyl peroxide, PE, and MWCNTs were reacted. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 957-965, 2011

Resume Objectif Le but de cette etude etait d’evaluer l’interet et les effets adverses d’un triple bloc (femoral, sciatique, obturateur) pour la realisation d’arthroscopie de genou (meniscectomie) en ambulatoire. Patients et methodes Cette etude prospective monocentrique descriptive incluait, apres consentement eclaire, des patients adultes (ASA 1–3) operes sous tribloc. Les blocs etaient realises au creux inguinal pour les nerfs femoral et obturateur et a la fesse (nerf sciatique), avec de la lidocaine ou de la mepivacaine 1,5 % (30–40 ml) selon une technique classique de neurostimulation. En cas de bloc incomplet a 40 minutes ou la survenue d’une douleur peroperatoire, une conversion en anesthesie generale (AG) etait realisee. Un observateur independant colligeait les delais de prise en charge, les evenements per et postoperatoires (en salle post-interventionnelle, au centre ambulatoire, et a distance par appels a j1, j3, j7 et visite chirurgicale a un mois). Resultats Trois cent douze patients ont ete selectionnes pour 115 triblocs realises, car 157 patients ont choisi l’AG, 19 la rachianesthesie et 21 presentes une contre-indication a l’ALR. Sur les 115 triblocs, 12 (10 %) patients ont necessite une AG avant incision (echecs d’installation/realisation). Le delai entre le debut du bloc et l’installation chirurgicale etait de 40 (10–60) minutes. En peroperatoire, 12 echecs (12 %) etaient lies a une douleur chirurgicale ( n = 7, 7 %) ou au garrot ( n = 5, 5 %). L’equipe chirurgicale donnait une note globale de confort chirurgical de 90 (60–100). La duree de sejour en SSPI etait de 15 (5–60) minutes et les scores de douleur inferieurs a 30/100 pour tous les patients jusqu’a la sixieme heure (aucun recours morphinique). A j0, 2 echecs de sortie d’ambulatoire sont notes (sans rapport avec le bloc). Le taux de NVPO est de 3,5 % a j0 et 8 % a j1. Le taux de paresthesie residuel est 1,7 % a j1 et 0,8 % a J3. Aucun effet adverse a j7 et un mois n’etait signale. La satisfaction des patients etait elevee, car 91 % « souhaitent la meme anesthesie ». Conclusion Le tribloc est une technique adaptee a l’anesthesie ambulatoire pour meniscectomie de genou : passage rapide en SSPI, NVPO limitees, analgesie efficace, retour rapide au domicile. La principale cause d’echec est liee a l’installation incomplete du bloc (10 % des cas) necessitant une sedation complementaire ou une conversion en AG. Compte tenu du long delai de preparation, une salle de preinduction est souhaitable pour faciliter l’organisation du programme operatoire.

A factorial design was used to understand how reaction parameters such as the monomer concentration, temperature, alkyl aluminium concentration, etc. influence the reaction rate and the polymer properties on two types of metallocene catalyst systems. The polymerisation kinetics and molecular weight distribution (MWD) obtained using a novel system (catalyst supported on an activated silica) were to those obtained with the reference system (same catalyst and silica but activated with MAO). As expected, the reaction temperature and the monomer concentration are the most important factors influencing the polymerisation rate, and this is independent of the catalytic system. Otherwise, the statistical approach allowed us to identify useful levels of MAO and comonomer at which to run in order to maximise the reaction rate.

Metallocene borohydride complexes {(Me2Si(C13H8)2)Nd(μ-BH4)[(μ-BH4)Li(THF)]}2 (1) and (Me2Si(2,7-tBu2C13H6)2)Nd(BH4)(μ-BH4)Li(ether)3 (2) were prepared by reaction of the dilithium salts of silylene-bridged bis(fluorenyl) ligands with the borohydride precursor Nd(BH4)3(THF)3. The solid state structures of dimeric 1 and monomeric 2 ate complexes were established by X-ray diffraction studies. We showed that these complexes used in combination with (nBu)(nOct)Mg are highly efficient for cyclocopolymerization of ethylene with butadiene leading to a new class of elastomers. Catalyst 1/(nBu)(nOct)Mg provided elastomers with a polyethylene skeleton incorporating unsaturated groups (trans double bond and pendant vinyl units) and 1,2-cyclohexane rings. These rings are formed via an intramolecular cyclization which occurs with a high trans selectivity. The investigation of catalyst 2/(nBu)(nOct)Mg has revealed that the tertio-butyl substitution in positions 2 and 7 of fluorenyl ligands influenced the microstructure...

Resume Apres une forte diminution des transfusions, la tendance depuis le debut des annees 2000 est a la remontee du nombre de transfusions. L’epargne transfusionnelle est limitee par des seuils transfusionnels qui ne doivent pas etre sous-evalues. Nous devons donc etre tres vigilants sur la strategie transfusionnelle perioperatoire qui doit etre encadree par les recommandations des societes savantes. Cette strategie comprend l’amelioration des techniques chirurgicales, l’utilisation optimale de la transfusion autologue perioperatoire et des medicaments et techniques favorisant l’epargne sanguine. Il s’agit donc d’une veritable strategie multimodale qui necessite en permanence l’evaluation des rapports benefices-risques de la reduction transfusionnelle en regard des indications de transfusion des produits sanguins labiles qu’il ne faut pas remettre en cause etant donne la grande securisation de la transfusion homologue.

Polyolefins account for more than half of worldwide production of thermoplastics. The majority is used as commodity polymers but they may also provide the starting backbones for original architectures. Most polyolefins are obtained by catalytic polymerization and this powerful technique may be used to produce polyolefins incorporating interesting functional groups that can serve as initiating sites for other successively applied polymerization techniques. This review describes the state of the art in strategies employing catalytic olefin polymerization followed by a living or controlled polymerization. The latter methodologies are classified according to the living/controlled polymerization technique used including anionic polymerization, nitroxide-mediated radical polymerization (NMRP), atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT).

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In slurry and gas phase catalytic ethylene polymerization processes, aluminum alkyl (AlR3) compounds are usually present inside the reactor and their role either as co-catalyst or scavenger is of considerable importance. Silica supported metallocene/methyl aluminoxane (MAO) catalysts show specific interactions with AlR3 compounds. Therefore, this study shows an attempt to analyze and compare the effect of concentration as well as type of commonly used AlR3 on slurry phase ethylene homopolymerization kinetics of silica supported (n-BuCp)2ZrCl2/MAO catalyst. The obtained results indicate that the lower the concentration of smaller AlR3 compounds, the higher the instantaneous catalytic activity. Concerning the polymer particle size distributions, a rise in fines generation has been observed with increasing AlR3 content inside the reactor. Finally, it has been shown that the addition of 2,6-di-tert-butyl-4-methylphenol (a substituted phenol) into the reactor containing AlR3 reduces the influence of AlR3 compounds on the reaction kinetics of silica supported metallocene/MAO catalysts. Polyethylene properties remain similar in all the studied scenarios. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45670.

We report a case of delayed rocuronium-induced deep block antagonization with sugammadex, thus requiring a total of three injections and a cumulative dose of 12 mg/kg over a 30 min period. The patient was an emergency case with full stomach that had required a rapid sequence induction. Because of hyperkaliemia due to an acute renal failure, rocuronium was preferred to succinylcholine. Use of sugammadex in the acute renal failure context is discussed.

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The synthesis of lanthanide(III) alkoxides has been described as a series of reactions for which the control of product purity is difficult. The possibility of using amide complexes, in the presence of alcohol, to produce alkoxides was investigated in homogeneous and heterogeneous media. The polymerization of e-caprolactone with alkoxides formed in situ was performed with and without excess alcohol. The latter system was efficient since the polymers were obtained in a short time period, with a well-controlled molecular weight and low polydispersity. The alcohol functionalized all the polymer chains.

In the current contribution it is demonstrated - for the first time - that poly(ethylene) (M(n) = 1,400 as well as 2,800 g · mol(-1) , PDI = 1.2) can be readily equipped with highly reactive cyclopentadienyl (Cp) end groups. The Cp terminal poly(ethylene) can subsequently be reacted in an efficient hetero Diels-Alder (HDA) reaction with macromolecules (poly(isobornyl acrylate) (M(n) = 4,600 g · mol(-1) , PDI = 1.10) and poly(styrene) (M(n) = 6,300 g · mol(-1) , PDI = 1.13) featuring strongly electron withdrawing thiocarbonyl thio end groups, prepared via reversible addition fragmentation chain transfer (RAFT) polymerization employing benzylpyridin-2-yldithioformate (BPDF) as transfer agent. The resulting block copolymers have been analyzed via high-temperature size exclusion chromatography (SEC) as well as nuclear magnetic resonance (NMR) spectroscopy. The current system allows for the removal of the excess of the non-poly(ethylene) containing segment via filtration of the poly(ethylene)-containing block copolymer. However, the reaction temperatures need to be judiciously selected. Characterization of the generated block copolymers at elevated temperatures can lead - depending on the block copolymer type - to the occurrence of retro Diels-Alder processes. The present study thus demonstrates that RAFT-HDA ligation can be effectively employed for the generation of block copolymers containing poly(ethylene) segments.

Background The purpose of this study was to compare parasacral and Winnie's single- or double-injection approaches for sciatic nerve block. Methods One hundred fifty adults scheduled to undergo lower limb surgery were randomized to receive on the sciatic nerve 20 ml ropivacaine, 0.75%: single bolus for parasacral and Winnie's single injection. For Winnie's double injection, the peroneal and tibial nerves received separately 10 ml plus 10 ml. Blocks were performed with the use of nerve stimulator (intensity < 0.5 mA, 1 Hz). For the parasacral method, a line was drawn between the posterior superior iliac spine and the ischial tuberosity; needle entry was at 6 cm inferior to the posterior superior iliac spine. Results The groups were similar. Time to perform the block was 2 (1-5) min for the parasacral method, with no difference from Winnie's single injection (3 [1-10] min), but was shorter with double injection (5.5 [2-15] min) (P = 0.0001). Onset of sensory block was similar in the parasacral (25 [7.5-50] min) and Winnie single-injection groups (25 [5-50] min) but significantly longer in the double-injection group (15 [5-50] min). Success rates for complete block were similar in the parasacral (66%) and Winnie's double-injection groups (68%) after 30 min but higher in the Winnie's single-injection group for tibial sensory and motor block (48%) (P < 0.017). Conclusion Time to perform a parasacral block was short, and the parasacral approach had a high success rate and a short onset time. Therefore, this block might be a useful alternative to Winnie's modification for sciatic nerve block.

Introduction En France, depuis quelques annees, le developpement de la chirurgie ambulatoire est devenu un objectif prioritaire de sante publique. La chirurgie orthopedique et traumatologique travaille aujourd’hui a elargir les indications de prise en charge ambulatoire. Une filiere de chirurgie traumatologique realisee de facon differee en ambulatoire apres retour a domicile a ete mise en place. L’objectif principal de cette etude etait d’evaluer le taux d’echec de la modalite ambulatoire, avec admission hospitaliere le soir de l’intervention, dans ce parcours. Materiel et methodes Une etude observationnelle, monocentrique, retrospective a ete realisee incluant tous les patients admis aux urgences pour un traumatisme orthopedique avec retour immediat a domicile et une prise en charge chirurgicale differee (IRB 13/12-02). La description de la filiere reposait sur une base de donnees colligeant les caracteristiques des patients, le type d’intervention et d’anesthesie, les complications immediates et l’evaluation a J1 apres retour a domicile. Une enquete de satisfaction a ete menee sur un echantillon de patients a l’aide d’un questionnaire cree pour l’etude. Resultats De septembre 2010 a novembre 2013, 98 patients ont ete inclus et analyses. Ils sont âges de 34 ans [24-46]. Quatre-vingt douze patients subissent une intervention du membre superieur. L’anesthesie locoregionale est utilisee pour 81 % d’entre eux. Au total, 3 patients ont ete hospitalises le soir de l’intervention. Aucun patient n’a ete admis a l’hopital avant la date operatoire, ni readmis apres le retour a domicile post interventionnel pour complication. La presence d’une douleur moderee a severe est retrouvee pour 25 % des patients a J1 post operatoire. Le delai moyen de prise en charge entre l’admission aux urgences et le jour operatoire est de 4 jours. L’enquete de satisfaction montrait une satisfaction globale pour plus de 90 % des patients. Discussion La filiere de traumatologie en ambulatoire represente une prise en charge moderne et efficace avec un niveau important de satisfaction des patients. Les actes de chirurgie traumatologique en urgence peuvent s’integrer dans un parcours de soin ambulatoire permettant la liberation de lits d’hospitalisation dans les services de chirurgie traumatologique et orthopedique.

Understanding the kinetics of olefin polymerization with Ziegler-Natta and related catalysts means identifying the main kinetic parameters such as k(p) and concentration of active sites. The high-pressure quenched-flow technique could be an absolute method for counting active sites and for activation studies of molecular catalysts. A kinetic study of metallocene catalysts and a phenoxy-imine titanium catalyst in the first instants of polymerization is presented in this paper.

The incorporation of functional groups at the end of polyolefin chains offers an opportunity to prepare polyolefin building blocks. The latter can be used to construct polymer architectures based on polyolefins with many desirable properties. For this purpose, the reactivity of the carbon-metal bond formed during a catalytic olefin polymerization process is particularly appealing. The possibility of taking advantage of this reactivity has indeed been enhanced by the discovery of systems in which fast and reversible chain transfer reactions between the active metal center and a main group metal centre are occurring. The recent developments of this catalyzed chain growth (CCG) concept are briefly reviewed. A specific system using a (C5Me5)2NdCl2Li(OEt2)2 complex in conjunction with n-butyloctylmagnesium is then employed to synthesize an array of end functional polyethylene chains. The potential of these building blocks to build up new macromolecular architectures is discussed.

The present paper highlights analogies between one of the most efficient control radical polymerization techniques namely the reversible addition–fragmentation chain transfer process, and the catalyzed polyethylene chain growth, the only technique that can controlled olefins polymerization through coordination chemistry under catalytic conditions.

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