Grubbs' and schrock's catalysts, ring opening metathesis polymerization and molecular brushes-synthesis, characterization, properties and applications

In this review, molecular brushes and other macromolecular architectures bearing a bottlebrush segment where the main chain is synthesized by ring opening metathesis polymerization (ROMP) mediated by Mo or Ru metal complexes are considered. A brief review of metathesis and ROMP is presented in order to understand the problems and the solutions provided through the years. The synthetic strategies towards bottlebrush copolymers are demonstrated and each one discussed separately. The initiators/catalysts for the synthesis of the backbone with ROMP are discussed. Syntheses of molecular brushes are presented. The most interesting properties of the bottlebrushes are detailed. Finally, the applications studied by different groups are presented. © 2019 by the authors

Grubbs’ and Schrock’s Catalysts, Ring Opening Metathesis Polymerization and Molecular Brushes—Synthesis, Characterization, Properties and Applications

In this review, molecular brushes and other macromolecular architectures bearing a bottlebrush segment where the main chain is synthesized by ring opening metathesis polymerization (ROMP) mediated by Mo or Ru metal complexes are considered. A brief review of metathesis and ROMP is presented in order to understand the problems and the solutions provided through the years. The synthetic strategies towards bottlebrush copolymers are demonstrated and each one discussed separately. The initiators/catalysts for the synthesis of the backbone with ROMP are discussed. Syntheses of molecular brushes are presented. The most interesting properties of the bottlebrushes are detailed. Finally, the applications studied by different groups are presented

Rhodium complexes with mixed trivalent phosphorus ligands: applications in homogenous catalysis

The synthesis of ten new rhodium complexes with trivalent phosphorus ligands has beenachieved :a) [RhCl(PPh3)2(P(OZ)3)], Z=Me (1), Et (2), nBu (3), Ph (4)b) [RhCl(P(OR)3)3], R=Me (5), Et (6), iPr (7), nBu (8)c) [RhCl(cod)(P(O-di-t-butylphenyl)3] (9) andd) [RhCl(CO)(P(O-di-t-butylphenyl)3)2] (10)The structure of the complexes has been characterized using analytic and NMR spectroscopicdata. Complexes (4) and (10) have been characterised with Χ ray crystallography. Complex (4)crystallizes in the orthorombic system Pca2(1) having elementary cell dimensions α=25,318(8)Å,β=19,138(6)Å and γ=19,097(6)Å, and complex (10) crystallizes in the monoclinic system C2/chaving elementary cell dimensions α=41,277(3) Å, β=9,0829(7)Å and γ=27,231(2)Å.Complexes (1), (4), (7), (10) are active catalysts. Complex (4) is a catalyst precursor for thehydrogenation of unsaturated organic substrates, alkene hydroformylation, allylic alkylation,decarbonylation of aldehydes, polymerization of 1,3-cyclohexadiene, norbornene and phenylacetylene,alkene isomerization. Complex (1) is a catalyst precursor for the hydrogenation of unsaturated organicsubstrates. Complex (7) is a catalyst precursor for allylic alkylation and the polymerization of 1,3-cyclohexadiene. Complex (10) is a catalyst precursor for alkene hydroformylation.Application of the QALE method shows that the chemical shifts δ(31Ρ PPh3) of the complexes(1)-(4) correlate linearly with respect to the parameters χd and πp of P(OΖ)3. From this correlation it isconcluded that the effect of the reduction of the σ donating ability of P(OΖ)3 relative to PPh3 results inshifting towards lower frequencies, whether the increasing of the π acceptor ability acts in theopposite direction.Επετεύχθη η σύνθεση δέκα νέων συμπλόκων ενώσεων του ροδίου με υποκαταστάτεςτρισθενούς φωσφόρου των τύπων :α) [RhCl(PPh3)2(P(OZ)3)], Z=Me (1), Et (2), nBu (3), Ph (4)β) [RhCl(P(OR)3)3], R=Me (5), Et (6), iPr (7), nBu (8)γ) [RhCl(cod)(P(O-di-t-butylphenyl)3] (9) καιδ) [RhCl(CO)(P(O-di-t-butylphenyl)3)2] (10)Ο χαρακτηρισμός της δομής τους έγινε βάσει αναλυτικών και NMR φασματοσκοπικώνδεδομένων. Τα σύμπλοκα (4) και (10) χαρακτηρίστηκαν με κρυσταλλογραφία ακτίνων Χ. Τοσύμπλοκο (4) κρυσταλλώνεται στο ορθορομβικό κρυσταλλικό σύστημα Pca2(1) με διαστάσειςστοιχειώδους κυψελίδας α=25,318(8)Å, β=19,138(6)Å και γ=19,097(6)Å και το σύμπλοκο (10)κρυσταλλώνεται στο μονοκλινές σύστημα C2/c με διαστάσεις στοιχειώδους κυψελίδας α=41,277(3)Å, β=9,0829(7)Å και γ=27,231(2)ÅΤα σύμπλοκα (1), (4), (7), (10) επιδεικνύουν καταλυτική δραστικότητα. Το (4) είναιπρόδρομος καταλύτης για την υδρογόνωση ακόρεστων οργανικών υποστρωμάτων, τηνυδροφορμυλίωση αλκενίων, την αλλυλική αλκυλίωση, την αποκαρβονυλίωση αλδεϋδών, τονπολυμερισμό του 1,3-κυκλοεξαδιενίου, του νορβορνενίου και του φαινυλακετυλενίου, τηνισομερείωση αλκενίων. Το (1) είναι πρόδρομος καταλύτης για την υδρογόνωση ακόρεστωνοργανικών υποστρωμάτων. Το (7) είναι πρόδρομος καταλύτης για την αλλυλική αλκυλίωση και τονπολυμερισμό του 1,3-κυκλοεξαδιενίου. Το (10) είναι πρόδρομος καταλύτης για την υδροφορμυλίωσηαλκενίων.H ανάλυση QALE των χημικών μετατοπίσεων δ(31Ρ PPh3) των συμπλόκων (1)-(4) συναρτήσειτων παραμέτρων χd και πp του P(OΖ)3, δείχνει ότι η μείωση της σ δοτικής ικανότητας του P(OΖ)3 ωςπρος την PPh3 προκαλεί μετατόπιση προς χαμηλότερες συχνότητες, ενώ, αντιστοίχως, η αύξηση της πδεκτικής ικανότητας προκαλεί μετατόπιση προς υψηλότερες συχνότητες

Synthesis and characterization of chiral poly(alkyl isocyanates) by coordination polymerization using a chiral half-titanocene complex

A new chiral half-titanocene complex, [CpTiCl2(O-(S)-2-Bu)], is synthesized and characterized by 1H and 13C NMR spectroscopy. This complex is employed for the coordination polymerization of n-butyl and n-hexyl- isocyanate leading to chiral polymers, as revealed by their CD spectra. Only the left-handed helix is produced, due to the chiral (S)-2-butoxy group, which is bound to the polymer chain end. The polymerization of 3-(triethoxysilyl)propyl isocyanate produces less soluble polymers. On the other hand, phenyl isocyanate reacts slowly with the complex leading quantitatively and selectively to triphenyl isocyanurate. 2-Ethylhexyl isocyanate is slowly and selectively cyclotrimerized in the presence of the half-titanocene complex. However, a statistical copolymer of 2-ethylhexyl isocyanate and hexyl isocyanate is produced. The reaction of benzyl isocyanate with the complex leads to a mixture of low molecular weight polymer and cyclotrimer. The polymers are characterized using SEC, NMR, and CD spectroscopy and their thermal properties are investigated by TGA/DSC analysis. © 2015 Wiley Periodicals, Inc

Polydl-lactide-b-[oligo(ethylene glycol) methyl ether (meth)acrylate)] block copolymers. Synthesis, characterization, micellization behavior in aqueous solutions and encapsulation of model hydrophobic compounds

A series of well-defined polydl -lactide-b-[oligo(ethylene glycol) methyl ether (meth)acrylate)] (PDLLA-b-POEG[M]A) functional amphiphilic diblock copolymers was synthesized by employing a multistep procedure involving: (a) ring-opening polymerization of dl -lactide using n-decanol and stannous octoate as the initiating system, (b) esterification reaction of the PDLLA hydroxyl end groups with 2-bromoisobutyryl bromide, (c) atom transfer radical polymerization of OEG(M)A with the newly created bromoisobutyryl initiating site, and (d) incorporation of biotin or folic acid at the POEGA chain ends using click chemistry. The products were characterized by NMR spectroscopy and SEC analysis. The aggregation behavior of the synthesized block copolymers was investigated by dynamic light scattering at 25°C in aqueous solutions. The hydrophobic model compounds Nile red and pyrene were efficiently incorporated into the copolymer aggregates in aqueous solutions. High partition coefficient values were determined by fluorescence spectroscopy. © 2020 Wiley Periodicals, Inc

Synthesis and characterization of chiral poly(l-lactide-b-hexyl isocyanate) macromonomers with norbornenyl end groups and their homopolymerization through ring opening metathesis polymerization to afford polymer brushes

We report the synthesis of the novel half-titanocene alkoxide complex bischloro-η5-cyclopentadienyl(bicyclo[2.2.1]-hept-5-en-2-oxy) titanium (IV), [CpTiCl2(O-NBE)]. This complex was employed for the synthesis of chiral poly(l-lactide-b-hexyl isocyanate) diblock copolymer bearing a norbornene end group with sequential addition of monomers. The poly(hexyl isocyanate) block is chiral due to the last l-lactide unit of the poly(l-lactide) block. This macromonomer was polymerized towards a chiral polymer brush structure with polynorbornene backbone and chiral poly(l-lactide-b-hexyl isocyanate) side chains using Grubbs first-generation catalyst. The polymers were characterized using size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), and circular dichroism (CD) spectroscopy and their thermal properties were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1102–1112. © 2017 Wiley Periodicals, Inc

Statistical copolymers of n-butyl vinyl ether and 2-chloroethyl vinyl ether via metallocene-mediated cationic polymerization. A scaffold for the synthesis of graft copolymers

The cationic statistical copolymerization of n-butyl (be) and 2-chloroethyl vinyl ether (CEVE), is efficiently conducted using bis(η5-cyclopentadienyl)dimethyl zirconium (Cp2ZrMe2) in combination with tetrakis(pentafluorophenyl)borate dimethylanilinum salt [B(C6F5)4]-[Me2NHPh]+, as an initiation system. The reactivity ratios are calculated using both linear graphical and non-linear methods. Structural parameters of the copolymers are obtained by calculating the dyad sequence fractions and the mean sequence length, which are derived using the monomer reactivity ratios. The glass transition temperatures (Tg) of the copolymers are measured by Differential Scanning Calorimetry (DSC), and the results are compared with predictions based on several theoretical models. The statistical copolymers are further employed as scaffolds for the synthesis of graft copolymers having poly(vinyl ether)s as a backbone and either poly(ε-caprolactone) (PCL) or poly(l-lactide) (PLLA) as side chains. Both the grafting "onto" and the grafting "from" methodologies are employed. The reaction sequence is monitored by Size Exclusion Chromatography (SEC), NMR and IR spectroscopies. The advantages and limitations of each approach are thoroughly examined. © 2019 by the authors

Polylactide-Grafted Metal-Alginate Aerogels

This work describes the synthesis of PLA-grafted M-alginate (g-M-alginate; M: Ca2+, Co2+, Ni2+, Cu2+) aerogels. DL-lactide (LA) was attached on the surface of preformed M-alginate beads and was polymerized, using stannous octoate as catalyst and the –OH groups of the alginate backbone as initiators/points of attachment. The material properties of g-M-alginate aerogels were not affected much by grafting, because the linear PLA chains grew on the M-alginate framework like a brush and did not bridge their points of attachment as in polyurea-crosslinked M-alginate aerogels. Thus, all g-M-alginate aerogels retained the fibrous morphology of their parent M-alginate aerogels, and they were lightweight (bulk densities up to 0.24 g cm−3), macroporous/mesoporous materials with high porosities (up to 96% v/v). The BET surface areas were in the range of 154–542 m2 g−1, depending on the metal, the nature of the alginate framework and the PLA content. The latter was found at about 15% w/w for Ca-and Ni-based materials and at about 29% w/w for Co-and Cu-based materials. Overall, we have demonstrated a new methodology for the functionalization of alginate aerogels that opens the way to the synthesis of polylactide-crosslinked alginate aerogels with the use of multifunctional monomers. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Synthesis and characterization of brush diblock and triblock copolymers bearing polynorbornene backbone and poly(l-lactide) and/or poly(hexyl isocyanate) side chains by a combination of coordination and ring opening metathesis polymerization

We report the synthesis of poly(l-lactide) and poly(hexyl isocyanate) macromonomers using bischloro-η5-cyclopentadienyl(bicyclo[2.2.1]-hept-5-en-2-oxy) Titanium (IV), [CpTiCl2(O-NBE)]. These macromonomers bearing a norbornene end group were polymerized towards brush copolymers employing Grubbs' first generation catalyst. Brush copolymers consisting of blocks with different side chains were synthesized. The polymers were characterized by Size Exclusion Chromatography, Nuclear Magnetic Resonance, and their thermal properties were investigated by Thermogravimetric Analysis, and Differential Scanning Calorimetry analysis. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3455–3465. © 2017 Wiley Periodicals, Inc