Rare-Earth Metallocenes for Polymerization of Olefins and Conjugated Dienes: from Fundamental Studies to Olefin Block Copolymers.

The various steps in the mechanism of olefin polymerizations mediated by neutral rare earth metallocene complexes are discussed. The complexes are either trivalent hydride and alkyl rare earth compounds or divalent metallocenes that are activated by the monomer via an oxidation step. The stereospecific polymerizations of conjugated dienes based on the association of a cationic metallocene complex and an alkylaluminum and the polymerization mechanism based on monomer insertion into an aluminum-carbon bond are also discussed. The exploitation of metallocene complexes for the copolymerization of olefins with conjugated dienes is the subject of a third part of this review. The synthesis of new elastomers called ethylene butadiene rubber (EBR) is highlighted. Finally, the use of rare-earth metallocenes in macromolecular engineering is detailed. This includes the synthesis of functional polyolefins and block copolymers including thermoplastic elastomers.

Nitriles as Functionalization and Coupling Agents for Polyolefins Obtained by Coordinative Chain Transfer Polymerization.

Coordinative chain transfer polymerization (CCTP) of ethylene and its copolymerization with 1,3-butadiene is conducted in toluene at 80 °C using a combination of {(Me2Si(C13H8)2)Nd(µ-BH4)[(µ-BH4)Li(THF)]}2 (1) metal complex and various organomagnesium compounds used as chain transfer agents including n-butyl-n-octyl-magnesium (BOMAG), n-butyl-mesityl-magnesium (n-BuMgMes), n-butyl-magnesium chloride (n-BuMgCl), n-pentyl-magnesium bromide (n-C5H11MgBr), pentanediyl-1,5-di(magnesium bromide) (PDMB) and isobutyl-magnesium chloride (i-BuMgCl). Kinetics and performance in terms of control of the (co)polymerization are comparatively discussed particularly considering the presence of ether and the nature of the organomagnesium compounds employed. Taking advantage of the well-known reactivity between nitrile and molecular organomagnesium compounds, the functionalization of the chains is further carried out by deactivation of the polymerization medium with benzonitrile or methoxybenzonitrile compounds leading to ketone ω-functionalized chains. The success of the functionalizations is extended to coupling strategies using dinitrile reagents and to the functionalization of high molar mass ethylene butadiene rubber (EBR).

Multiblock Copolymers Based on Highly Crystalline Polyethylene and Soft Poly(ethylene-co-butadiene) Segments: Towards Polyolefin Thermoplastic Elastomers.

Block copolymers based on polyethylene (PE) and ethylene butadiene rubber (EBR) were obtained by successive controlled coordinative chain transfer polymerization (CCTP) of a mixture of ethylene and butadiene (80/20) and pure ethylene. EBR-b-PE diblock copolymers were synthesized using the {Me2 Si(C13 H8 )2 Nd(BH4 )2 Li(THF)}2 complex in combination with n-butyl,n-octyl magnesium (BOMAG) used as both the alkylating and chain transfer agent (CTA). Triblock and multiblock copolymers featuring highly semi-crystalline PE hard segments and soft EBR segments were further obtained by the development of a bimetallic CTA, the pentanediyl-1,5-di(magnesium bromide) (PDMB). These new block copolymers undergo crystallization-driven organization into lamellar structures and exhibit a variety of mechanical properties, including excellent extensibility and elastic recovery in the case of triblock and multiblock copolymers.

Deciphering Siloxane Bond Exchanges: From a Molecular Study to Vitrimerization and Recycling of Silicone Elastomers.

The activity of various additives promoting siloxane equilibration reactions is examined and quantified on model compounds. We found in particular that the "superbase" phosphazene derivative P4 -t Bu can promote very fast exchanges (a few seconds at 90 °C) even at low concentration (<0.1 wt %). We demonstrate that permanent silicone networks can be transformed into reprocessable and recyclable dynamic networks by mere introduction of such additives. Annealing at high temperature degrades the additives and deactivates the dynamic features of the silicone networks, reverting them back into permanent networks. A simple rheological experiment and the corresponding model allow to extract the critical kinetic parameters to predict and control such deactivations.

Telemedicine for Preanesthesia Consultations During the First COVID-19 Lockdown.

Introduction: In an effort to avoid travel and interpersonal contact, the COVID-19 health crisis was an opportunity to offer preanesthesia teleconsultation (TCs) to patients scheduled for surgery. Materials and Methods: We studied the technical feasibility and patient experiences of these TCs using a 4-point Likert scale questionnaire. Results: Eighty-six patients out of 139 responded. Technical difficulties (no connection, picture, or sound) occurred in 24% of cases. The patient's experience was considered very positive both in terms of feelings and understanding instructions: 4 (4-4). No deprogramming was required. Conclusion: TCs were approved by patients despite technical problems. Further studies are required to ensure that this type of consultation is not inferior to face-to-face consultations. NCT04920604.

How traditional and digital analytics interventions can enhance lung-protective ventilation strategies during general anaesthesia: A two-year quality improvement project analysis.

PURPOSE: This quality improvement project evaluated interventions implemented to enhance individual adherence to a lung-protective ventilation strategy and its triad: low tidal volume, PEEP ≥ 5, recruitment manoeuvres. METHODS: For two years, nine anaesthesia workstations were connected to an automated cloud-based analytics software tool, which automatically recorded ventilation parameters as soon as a new patient case was opened. Four quality improvement periods were determined over the first year: baseline, intervention, no intervention, intervention + digital. In the second year, the digital strategy was continued for nine months, followed by a final "overtime" period. Baseline and no intervention periods included no training. The intervention period included both conventional and educational programs. The digital period included pop-up messages, which automatically appeared on the screen of the anaesthesia data management system when patients were intubated. The primary endpoint was provider adherence to the recommended triad. RESULTS: From October 2018 to December 2020, 12,883 procedures were performed. Data were available for 8968 procedures: baseline (n = 2361), intervention (n = 2423), no intervention (n = 1064), intervention + digital (n = 1862), overtime (n = 1258). Age, Predicted Body Weight, ASA score, type of surgery and airway management were similar between periods. At baseline, 75.2% of procedures reported low tidal volume but only 6.9% involved the complete triad. At over time, Triad was 22% (p < 0.001). Over study period, each parameter of the Triad (RM, Vt and Peep) increased (p < 0.001 vs. baseline), driving pressure decreased although EtCO2 and plateau pressure had not changed. CONCLUSION: Training with the help of digital apps improved LPV adherence over time.

Ethylene-Coordinative Chain-Transfer Polymerization-Induced Self-Assembly (CCTPISA).

Block copolymers based on ethylene (E) and butadiene (B) were prepared using the ansa-bis(fluorenyl) complex {Me2 Si(C13 H8 )2 Nd(BH4 )2 Li(THF)}2 in combination with (n-Bu)(n-Oct)Mg (BOMAG) as a chain-transfer agent. The diblock copolymers incorporating a soft poly(ethylene-co-butadiene) segment, called ethylene butadiene rubber (EBR), and a hard polyethylene (PE) one were obtained by simply adjusting the different feeds of monomers during the polymerization. The soluble EBR block was formed first by feeding the catalytic system dissolved in toluene at 70 °C with a mixture of ethylene and butadiene (E/B molar ratio 80 : 20). Then the feeding was stopped leading to the consumption of a large part of the residual monomers. The reactor was finally fed with ethylene to form the PE block. By varying the molar mass of the latter, it is shown that the resulting soft-b-hard block copolymers can self-assemble simultaneously to the growth of the PE block in agreement with a polymerization-induced self-assembly (PISA) mechanism. The self-assembly is discussed considering the reaction conditions, the crystallization of the PE block, and the polymerization mechanism involved.

Switch from Anionic Polymerization to Coordinative Chain Transfer Polymerization: A Valuable Strategy to Make Olefin Block Copolymers.

Anionic polymerization of butadiene or/and styrene is performed with lithium initiators, functional or not. The polymer chains are subsequently transferred to magnesium. The resulting polymeryl-magnesium compounds were combined with {(Me2 Si(C13 H8 )2 )Nd(µ-BH4 )[(µ-BH4 )Li(THF)]}2 metallocene complex to act as macromolecular chain transfer agents (macroCTAs) in coordinative chain transfer polymerization (CCTP) of ethylene (E) or its copolymerization (CCTcoP) with butadiene (B). Block copolymers were produced for the first time by this switch from anionic polymerization to CCTP. Hard and soft blocks such as PB, polystyrene (PS), poly(styrene-co-butadiene) (SBR) obtained by anionic polymerization and PE or poly(ethylene-co-butadiene) (EBR) produced by CCT(co)P were combined and the corresponding structures were characterized.

Feasibility of remote digital monitoring using wireless Bluetooth monitors, the Smart Angel™ app and an original web platform for patients following outpatient surgery: a prospective observational pilot study.

BACKGROUND: Remote monitoring of mean arterial blood pressure (MAP), heart rate (HR) or oxygen saturation (SpO2) remains a challenge in outpatient surgery. This study evaluates a new digital technology (Smart Angel™) for remotely monitoring hemodynamic data in real time: data transmitted from the patient's home to a central server, using a dedicated web-based software package. METHODS: Adults scheduled for elective outpatient surgery were prospectively enrolled. In the first 5 postoperative days, patients completed a self-report questionnaire (pain, comfort, nausea, vomiting) and recorded SpO2, HR and MAP via two wireless Bluetooth monitors connected to a 4G tablet to transmit the data to a website, in real time, using Smart Angel™ software. Before transmission to the website, these data were also self-reported by the patient on a paper form. The primary outcome was the proportion of variables (self-monitored physiological data + questionnaire scores) correctly transmitted to the hospital via the system compared with the paper version. On Day 5, a system usability scale survey (SUS score 1-100) was also attributed. RESULTS: From May 2018 to September 2018, data were available for 29 out of 30 patients enrolled (1 patient was not discharged from hospital after surgery). The remote monitoring technology recorded 2038 data items (62%) compared with 2656 (82%) items recorded on the paper form (p = 0.001). The most common errors with the remote technology were software malfunctioning when starting the MAP monitor and malfunctioning between the tablet and the Bluetooth monitor. No serious adverse events were noted. The SUS score for the system was 85 (68-93) for 26 patients. CONCLUSION: This work evaluates the ability of a pilot system for monitoring remote physiological data using digital technology after ambulatory surgery and highlights the digital limitations of this technology. Technological improvements are required to reduce malfunctioning (4G access, transmission between apps). TRIAL REGISTRATION: ClinicalTrials.gov ( NCT03464721 ) (March 8, 2018).

30 TW and 33 fs pulses delivered by a Ti:Sa amplifier system seeded with a frequency-doubled fiber laser.

We report a full experimental comparison study on the injection of a Ti:Sa multi-terawatt amplifier chain with a standard 15 fs Ti:Sa oscillator and 35 fs frequency-doubled fiber oscillator. The study highlights that the Ti:Sa oscillator, with high performance in terms of pulse duration and spectral width, can be replaced by the frequency-doubled fiber oscillator to seed Ti:Sa amplifier chains almost without any compromise on the output pulse duration and picosecond contrast. Finally, we demonstrate for the first time to our knowledge a 30 TW and 33 fs Ti:Sa amplifier injected by a fiber oscillator.

Impact of a preoperative pharmaceutical consultation in scheduled orthopedic surgery on admission: a prospective observational study.

BACKGROUND: Medication errors have a high prevalence in surgery and management of home medication is strongly involved in these errors. In scheduled surgery, the preoperative consultation is a privileged time to inform the patient about the management of her/his home medication before admission. This study assessed the impact of a pre-anesthesia best possible medication history (PA-BPMH) on admission. The PA-BPMH was performed by a clinical pharmacist prior to the anesthesia consultation for anesthesiologists to prescribe admission medical orders for scheduled orthopedic surgery patients. METHODS: This was a prospective observational study which was carried out in an orthopedic surgery department. All patients over 18 years old with an elective orthopedic surgery were eligible except ambulatory surgery patients. The pharmacist registered the PA-BPMH into the software making it available for anesthesiologists for the pre-admission medication order. Finally, a medication reconciliation was performed at admission. The main outcome was the percentage of patients with at least one unintended medication discrepancy (UMD) at admission. The nature, potential clinical impact and acceptance rate of each UMD detected were assessed. Also, the PA-BPMH process was described and patients and anesthesiologists satisfaction was evaluated. RESULTS: A total of 455 patients had a pharmaceutical consultation. Medication reconciliation was performed at admission for 360 patients. Overall, at least one UMD was observed in 13.0% of patients (n = 47). A total of 63 UMD were detected. The most common type of UMD was omission (25.4%) and incorrect drug (23.8%).Two UMD (3.2%) were evaluated as life threatening. All the UMD detected were corrected on the admission medication order. CONCLUSION: A preoperative pharmacist-anesthesiologist teamwork seems to improve the safety of perioperative management of home medication for scheduled orthopedic surgery patients. This process needs a randomized clinical trial across a wider range of surgeries before its implementation.

Polyethylene Aerogels with Combined Physical and Chemical Crosslinking: Improved Mechanical Resilience and Shape-Memory Properties.

While the introduction of polymers into aerogels strongly enhances their toughness, truly elastic monolithic aerogels which restore their dimensions upon extensive compression are still challenging to synthesize. In this context hydrophobic semi-crystalline polymers with low glass transition temperatures, and combined stiffness and flexibility, have only recently attracted attention. Shown here is that polyethylene aerogels with a low density, and combined chemical crosslinking and high crystallinity, display high moduli and excellent mechanical resilience. To maximize the crystallinity of these aerogels while maintaining a high crosslinking density, polyethylene networks with well-defined segments were synthesized by hydrosilylation crosslinking of telechelic, vinyl-functionalized oligomers obtained from catalyzed chain-growth polymerization. Recoverable deformations both above and below the melting temperature of polyethylene affords remarkable shape-memory properties.

Comparison of axillary nerve block duration using mepivacaine in non-insulin diabetic or renal insufficiency patients: a controlled observational matched multicenter trial.

BACKGROUND: Although studies in diabetic patients demonstrated delayed recovery after long-acting local anesthetic, its effects with short-acting LA remains to be determined. Using mepivacaine, the authors evaluated the duration of axillary nerve blocks in diabetic (DP), renal failure (creatinine clearance <30 mL.min-1) (RP) and healthy patients (HP). METHODS: We prospectively included consecutive patients aged 18-80 years, with DP (N.=37), RP (N.=32) and HP (N.=48) scheduled for distal upper limb surgery. Before surgery, an axillary nerve block (20 mL mepivacaine 15 mg.mL-1) was performed with an ultrasound approach combined with nerve stimulation. Five mL was injected for each nerve: median, ulnar, radial, musculocutaneous nerves. The primary endpoint measured was the duration of sensory block. For statistical analysis, each HP patient was matched with RP and DP patient (1:1), with regards to age (range±5 years) and sex. RESULTS: Patient characteristics were similar between groups. Creatinine clearance was 14±8 mL.min-1 in RP group and HbA1c (%) was 7.5±1.5 in DP group. Mean duration of diabetic or renal insufficiency illness were respectively eight and 12 years. Onset time for sensory and motor blocks were similar between groups. Average time for sensory block duration was similar between DP vs. HP (235±52 vs. 230±54 min, P=0.71); and between RP vs. HP (234±51 vs. 229±57 min, P=0.65). CONCLUSIONS: The short-acting LA (mepivacaine) are associated with similar pharmacodynamic effects in diabetic and renal failure patients as compared with healthy patients.

Monofunctional and Telechelic Polyethylenes Carrying Phosphonic Acid End Groups.

Monofunctional or telechelic polyethylenes (PEs) carrying phosphonic acid end groups are obtained from functional PE produced by catalyzed chain growth (CCG) on magnesium. CCG is first used to produce iodo-end-functionalized PE (PE-I) that is efficiently turned into phosphonate end-functionalized PE (PE-P(O)(OEt)2 ) in the presence of triethylphosphite through the Michaelis-Arbuzov reaction. A simple treatment of the resulting PE-P(O)(OEt)2 with bromotrimethylsilane leads to the targeted phosphonic acid end-functionalized PE (PE-P(O)(OH)2 ) for the first time. Vinyl-end-functionalized analogs (Vin-PE-P(O)(OEt)2 ) are produced using vinyl-end-functionalized PE-I (Vin-PE-I) recently obtained through CCG. A cross-metathesis reaction is then employed to couple Vin-PE-P(O)(OEt)2 and produce after treatment with bromotrimethylsilane the corresponding unprecedented α-ω-(diphosphonic acid) telechelic PE ((OH)2 (O)P-PE-P(O)(OH)2 ).

Coherent beam combining of seven fiber chirped-pulse amplifiers using an interferometric phase measurement.

Coherent beam combining in tiled-aperture configuration is demonstrated on seven femtosecond fiber amplifiers using an interferometric phase measurement technique. The residual phase error between two fibers is as low as λ/55 RMS and a combination efficiency of 48% has been achieved. The combined pulses are compressed to 216 fs, delivering 71 W average power at a repetition rate of 55 MHz. Operating the laser system in a nonlinear regime with an estimated B-integral of 5 rad yields a combining efficiency of 45% with the same phase stability. These results pave the way to very large high-power and high energy coherent beam combining systems.

Polyolefins, a Success Story.

This paper reports the principal discoveries which have played a major role in the polyolefin field and have positioned polyolefins as the most produced plastics. The early development of polyolefins covering the production of LDPE (Low density polyethylene) at ICI (Imperial Chemical Industries) and the discovery of Phillips or Ziegler-Natta catalysts are highlighted in the first section. In the second part, the impact of the implementation of molecular catalysts on the research in polyolefins is discussed together with the most recent advances leading to high-performance tailor-made resins.

The design of a bipodal bis(pentafluorophenoxy)aluminate supported on silica as an activator for ethylene polymerization using surface organometallic chemistry.

A new class of well-defined activating supports for olefin polymerization was obtained via the surface organometallic chemistry approach. High activities in slurry polymerization of ethylene along with industrial-grade physical properties of the resulting polyethylene were obtained when these activators were combined with metallocene complexes in the presence of triisobutylaluminium.

Polyboramines for Hydrogen Release: Polymers Containing Lewis Pairs in their Backbone.

The one-step polycondensation of diamines and diboranes triggered by the in situ deprotonation of the diammonium salts and concomitant reduction of bisboronic acids leads to the assembly of polymer chains through multiple Lewis pairing in their backbone. These new polyboramines are dihydrogen reservoirs that can be used for the hydrogenation of imines and carbonyl compounds. They also display a unique dihydrogen thermal release profile that is a direct consequence of the insertion of the amine-borane linkages in the polymeric backbone.

Toward Anisotropic Hybrid Materials: Directional Crystallization of Amphiphilic Polyoxazoline-Based Triblock Terpolymers.

We present the design and synthesis of a linear ABC triblock terpolymer for the bottom-up synthesis of anisotropic organic/inorganic hybrid materials: polyethylene-block-poly(2-(4-(tert-butoxycarbonyl)amino)butyl-2-oxazoline)-block-poly(2-iso-propyl-2-oxazoline) (PE-b-PBocAmOx-b-PiPrOx). The synthesis was realized via the covalent linkage of azide-functionalized polyethylene and alkyne functionalized poly(2-alkyl-2-oxazoline) (POx)-based diblock copolymers exploiting copper-catalyzed azide-alkyne cycloaddition (CuAAC) chemistry. After purification of the resulting triblock terpolymer, the middle block was deprotected, resulting in a primary amine in the side chain. In the next step, solution self-assembly into core-shell-corona micelles in aqueous solution was investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Subsequent directional crystallization of the corona-forming block, poly(2-iso-propyl-2-oxazoline), led to the formation of anisotropic superstructures as demonstrated by electron microscopy (SEM and TEM). We present hypotheses concerning the aggregation mechanism as well as first promising results regarding the selective loading of individual domains within such anisotropic nanostructures with metal nanoparticles (Au, Fe3O4).

Divinyl-end-functionalized polyethylenes: ready access to a range of telechelic polyethylenes through thiol-ene reactions.

Telechelic α,ω-iodo-vinyl-polyethylenes (Vin-PE-I) were obtained by catalytic ethylene polymerization in the presence of [(C5 Me5 )2 NdCl2 Li(OEt2 )2 ] in combination with a functionalized chain-transfer agent, namely, di(10-undecenyl)magnesium, followed by treatment of the resulting di(vinylpolyethylenyl)magnesium compounds ((vinyl-PE)2 Mg) with I2 . The iodo-functionalized vinylpolyethylenes (Vin-PE-I) were transformed into unique divinyl-functionalized polyethylenes (Vin-PE-Vin) by simple treatment with tBuOK in toluene at 95 °C. Thiol-ene reactions were then successfully performed on Vin-PE-Vin with functionalized thiols in the presence of AIBN. A range of homobifunctional telechelic polyethylenes were obtained on which a hydroxy, diol, carboxylic acid, amine, ammonium chloride, trimethoxysilyl, chloro, or fluoroalkyl group was installed quantitatively at each chain end.