In situ generated half-lanthanidocene based catalysts for the controlled oligomerisation of styrene: Selectivity, block copolymerisation and chain transfer

International audienceThe Cp*Nd(BH4)2(THF)2/n-butylethylmagnesium combination affords a controlled and syndioselective oligomerisation of styrene. Living oligostyrenes can be used as macromonomers for block copolymerisation, leading to the unprecedented synthesis of a (polystyrene)-block- (1,4-trans polyisoprene) copolymer. Reversible transmetallation between the neodymium and the magnesium atom is further established with a transfer efficiency close to 100%

A New Family of Styrene/Diene Rubbers

International audienceThe insertion of single styrene units into polyisoprene is demonstrated using borohydrido rare earth/dialkylmagnesium systems. This yields a new family of styrene/diene copolymers (SBR rubbers). The resulting poly[(1,4-trans-isoprene)-co-styrene] exhibits quite narrow molecular weight distributions, up to 30% inserted styrene, and a 96–98% 1,4-trans-microstructure. The presence of a bulky and electron-rich ligand in the coordination sphere of the metal leads to an increase of the amount of styrene inserted and narrower chemical composition and molecular weight distributions. The presence of significant quantities of styrene in the medium does not alter the selectivity of the reaction, in contrast with cis-specific polymerizations

New ionic half-metallocenes of early lanthanides

International audienceWe present in this study a new and one-step method allowing the preparation of an unprecedented family of stable half-lanthanidocenes. X-ray analysis shows that the isolated compounds all display the same ionic Ln–Mg bimetallic structure consisting of two anionic (CpR)Ln(BH4)3 species and one cationic Mg(THF)6 (CpR =C5Me5, Ln = Nd, 1a, Ln = La, 1b; CpR =C5H5, Ln = Nd, 2a; CpR =C5H2Ph3, Ln = Nd, 3a). Such complexes display high stability with respect to disproportionation in solution. Combined with dialkylmagnesium, neodymium complexes provide powerful catalysts for stereospecific isoprene polymerisation

“Half-lanthanidocenes catalysts via the "borohydride/alkyl" route: A simple approach of ligand screening for the controlled polymerization of styrene.”

International audienceThe ‘‘borohydride/alkyl'' (B/A) route initially reported for isoprene has been applied successfully to the polymerization of styrene. This method provides via an in situ approach an interesting tool for the assessment of the influence of a ligand on the performance of half-lanthanidocene catalysts. All systems lead to well controlled oligomerization/polymerization processes. This method is thus a convenient tool for the controlled polymerization of styrene starting from a common trisborohydride precursor and commercial ligands. The influence of the nature of several ligands on the activity could be established, with trends corresponding to those obtained starting from the isolated precursors: HCp = HCpPh3 > HCp* (Cp = C5H5; CpPh3 = 1; 2; 4-Ph3C5H2; Cp* = C5Me5). These results suggest an influence of the electron donating ability of the ligand rather than steric requirements

Intelligent Machine Learning: Tailor-Making Macromolecules

Nowadays, polymer reaction engineers seek robust and effective tools to synthesize complex macromolecules with well-defined and desirable microstructural and architectural characteristics. Over the past few decades, several promising approaches, such as controlled living (co)polymerization systems and chain-shuttling reactions have been proposed and widely applied to synthesize rather complex macromolecules with controlled monomer sequences. Despite the unique potential of the newly developed techniques, tailor-making the microstructure of macromolecules by suggesting the most appropriate polymerization recipe still remains a very challenging task. In the current work, two versatile and powerful tools capable of effectively addressing the aforementioned questions have been proposed and successfully put into practice. The two tools are established through the amalgamation of the Kinetic Monte Carlo simulation approach and machine learning techniques. The former, an intelligent modeling tool, is able to model and visualize the intricate inter-relationships of polymerization recipes/conditions (as input variables) and microstructural features of the produced macromolecules (as responses). The latter is capable of precisely predicting optimal copolymerization conditions to simultaneously satisfy all predefined microstructural features. The effectiveness of the proposed intelligent modeling and optimization techniques for solving this extremely important ‘inverse’ engineering problem was successfully examined by investigating the possibility of tailor-making the microstructure of Olefin Block Copolymers via chain-shuttling coordination polymerization

Poly(L-lactide) Epimerization and Chain Scission in the Presence of Organic Bases

peer reviewedOrganocatalysis for polymer chemistry has become a subject of significant interest in the last two decades. In this contribution, we have studied the evolution of the microstructure of poly(L-lactide) in solution in toluene at 105 °C in the presence of various organocatalysts. Weak bases such as triethylamine and DMAP (4-dimethylaminopyridine) lead to a low extent of epimerization and a chain scission reaction. The DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) amidine induces in turn important extents of both epimerization (up to 37% D-stereoisomer formation) and chain scission. This has been tentatively attributed to a nucleophilic mechanism. Cinchona alkaloids lead to only a modest amount of epimerization. Phosphazene bases are in turn rather active, especially for high catalytic loadings (>1 mol %). The chain scission observed in this case is proposed to occur via a base-catalyzed hydrolysis mechanism. Finally, it is shown that combining an organic base with an acid can lead to a synergistic effect regarding notably the chain scission reaction

Towards Olefin Multi-block Copolymers with Tailored Properties: A Molecular Perspective

This is an Accepted Manuscript of an article published by Macromolecular Theory and Simulations (MTS), of Wiley. Mohammadi, Y., Saeb, M. R., Penlidis, A., Jabbari, E., Stadler, F. J., Zinck, P., & Vivaldo‐Lima, E. (2021). Toward olefin multiblock copolymers with tailored properties: A molecular perspective. Macromolecular Theory and Simulations, 30(3), 2100003. https://doi.org/10.1002/mats.202100003Recent progress in macromolecular reaction engineering has enabled the synthesis of sequence-controlled polymers. The advent of Olefin Block Copolymers (OBCs) via chain shuttling polymerization of ethylene with α-olefins has opened new horizons for the synthesis of polyolefins having a dual character of thermoplastics and elastomers. Nevertheless, the use of two catalysts with different comonomer selectivities and a chain shuttling agent, dragging and dropping live chains between active catalyst centers, made precise tailoring of OBCs microstructure containing hard and soft units a feasible challenge. This work discusses the possibility of predicting properties of OBCs from its simulated molecular patterns. The microstructural characteristics of OBCs are discussed in terms of topology-related and property-related features. An intelligent tool, which combines the benefits of Kinetic Monte Carlo simulation and Artificial Neural Network modeling, was used to explore the connection between polymerization recipe (catalyst composition, ethylene to 1-octene monomer ratio, and chain shuttling agent level) and topology-related as well as property-related microstructural features. The properties of target OBCs are reflected in the hard block percent, the number of 1-octene units in the copolymer chains, and the longest ethylene sequence length of the hard and soft segments

Polymer "ruthenium-cyclopentadienyl" conjugates - New emerging anti-cancer drugs

In this work, we aimed to understand the biological activity and the mechanism of action of three polymer-'ruthenium-cyclopentadienyl' conjugates (RuPMC) and a low molecular weight parental compound (Ru1) in cancer cells. Several biological assays were performed in ovarian (A2780) and breast (MCF7, MDA-MB-231) human cancer derived cell lines as well as in A2780cis, a cisplatin resistant cancer cell line. Our results show that all compounds have high activity towards cancer cells with low IC50 values in the micromolar range. We observed that all Ru-PMC compounds are mainly found inside the cells, in contrast with the parental low molecular weight compound Ru1 that was mainly found at the membrane. All compounds induced mitochondrial alterations. PMC3 and Ru1 caused F-actin cytoskeleton morphology changes and reduced the clonogenic ability of the cells. The conjugate PMC3 induced apoptosis at low concentrations comparing to cisplatin and could overcame the platinum resistance of A2780cis cancer cells. A proteomic analysis showed that these compounds induce alterations in several cellular proteins which are related to the phenotypic disorders induced by them.Our results suggest that PMC3 is foreseen as a lead candidate to future studies and acting through a different mechanism of action than cisplatin. Here we established the potential of these Ru compounds as new metallodrugs for cancer chemotherapy.This work was financed by the Portuguese Foundation for Science and Technology (Fundacao para a Ciencia e a Tecnologia, FCT) within the scope of projects UID/QUI/00100/2013 and PTDC/QUI-QIN/28662/2017. This work was supported by the strategic program UID/BIA/04050/2013 (POCI-01-0145-FEDER-007569) funded by national funds through the FCT I.P. and by the ERDF through the COMPETE2020 - Programa Operacional Competitividade e Internacionalizacao (POCI). Andreia Valente acknowledges the COST action CM1302 (SIPs), the Investigator FCT2013 Initiative for the project IF/01302/2013 (acknowledging FCT, as well as POPH and FSE - European Social Fund) and the Royal Society of Chemistry's Research Fund. Pierre Falson and Elisabeta Comsa warmly acknowledge Thibault Andrieu from the cytometry plateau of SFR bioscience -UMS 3444- at Lyon-Gerland, France for assistance on CytoF. This work was also supported by the Marie Curie Initial Training Network: FP7-PEOPLE-2012-ITN proposal no 317297 - acronym GLYCOPHARM and PITN-GA-2012-317297. The high resolution mass spectrometer at CIRE-PAIB was financed (SMHART project no3069) by the European Regional Development Fund (ERDF), the Conseil Regional du Centre, the French National Institute for Agricultural Research (INRA) and the French National Institute of Health and Medical Research (Inserm)