Acyclic Diene Metathesis Polymerization Research Articles

Synthesis of precision polymers with regularly placed perfluoroalkyl segments and sulfonic acid groups via ADMET polymerization and internal alkene modification

We demonstrate the facile synthesis of a new type of precision polymers containing periodically placed perfluoroalkyl segments and sulfonic acid groups via acyclic diene metathesis (ADMET) polymerization of designed diene monomers and the subsequent postmodification of the internal CC bonds. Two diene monomers containing perfluoroalkyl segments [-(CF2)n-, n = 4 and 6] were synthesized through the atom transfer radical addition (ATRA) of dodecafluoro-1, 6-diiodohexane and octafluoro-1, 4-diiodobutane with 1,5-hexadiene and the subsequent deiodination. ADMET polymerization of these two monomers with Grubbs-I catalyst led to periodic polymers containing perfluoroalkyl segments and internal CC bonds. Subsequent postpolymerization modification with thiolacetic acid and the following oxidation with hydrogen peroxide afforded the final polymers. The polymers were characterized by NMR, GPC, and FTIR, and the thermal properties of the final copolymers were investigated by DSC and TGA. These polymers exhibited high thermal stability as compared to other precisely sulfonated polyethylene analogues; therefore, they may be potentially investigated as efficient proton transport membranes.

Synthesis and Catalytic Properties of Sulfur-Chelated Ruthenium Benzylidenes Bearing a Cyclic (Alkyl)(amino)carbene Ligand

Sulfur-chelated ruthenium olefin metathesis precatalysts that possess cyclic (alkyl)(amino)carbenes (CAAC) can benefit from the synergetic effect of both ligands. Changing the steric bulk of the CAAC ligand by using different substitution patterns was shown to affect the geometry of the complexes produced and determined whether the complexes could be catalytically dormant. The cis-dichloro latent catalysts could be activated both by heat or light, even in the visible region, for representative acyclic diene metathesis and ring-opening metathesis polymerization reactions, olefin cross-metathesis, and ring-closing metathesis without isomerization byproducts. Thus, these complexes were shown to combine the uniqueness of CAAC-containing Ru olefin metathesis catalysts with the advantage of the thermal and photolatency imposed by sulfur chelation of the benzylidene.

Functional Polyethylenes with Precisely Placed Thioethers and Sulfoniums through Thiol–Ene Polymerization

The precise functionalization of polyethylenes, often accomplished through acyclic diene metathesis polymerization (ADMET), is a significant area of research that has improved polyethylene properties and performance. Here, the synthesis of precisely functionalized polyethylenes was accomplished using the thiol–ene step-growth (TES) polymerization. The simplicity and versatility of this technique allowed for the synthesis of a variety of polymers and enabled the study of carbon spacer length between and repeat unit symmetry about the resulting backbone thioether moiety. In addition, the backbone thioethers of some samples were functionalized postpolymerization with methyl triflate to produce polyethylenes containing sulfonium cations. All polymers were then characterized for their thermal stability, crystallinity, and morphology using differential scanning calorimetry (DSC) and X-ray scattering. While the carbon spacer length and repeat unit symmetry had no effect on polymer thermal stability, the incorpor...

Noticeable Chiral Center Dependence of Signs and Magnitudes in Circular Dichroism (CD) and Circularly Polarized Luminescence (CPL) Spectra ofall-trans-Poly(9,9-dialkylfluorene-2,7-vinylene)s Bearing Chiral Alkyl Side Chains in Solution, Aggregates, and Thin Films

Effects of chiral alkyl side chains in poly(9,9-dialkyl-fluorene-2,7-vinylene)s [PFVs, (S)-3-methylpentyl (3mpe), (S)-4-methylhexyl (4mhex), (S)-5-methylheptyl (5mhep), (S)-6-methyloctyl (6moct), and (S)-3,7-dimethyloctyl (dmo)] toward aggregation-induced circular dichroism (AICD) and circularly polarized luminescence (AICPL) and CD/CPL spectra in solution and in thin film have been explored. The (all-trans) PFV samples with similar conjugation repeat units containing well-defined (vinyl) end groups were prepared by acyclic diene metathesis polymerization using Ru catalyst. The PFV aggregates, prepared in situ in a mixed solution of CHCl3/MeOH, showed clear CD signals ascribed to AICD, whereas these samples showed CD-silent in the CHCl3 solution. The absolute magnitude (gCD value) was affected by the chiral side chains (without obey the even–odd rule) and increased in the order 3mpe, 5mhep < 4mhex < dmo < 6mcot. Both the 6-moct and dmo aggregates showed clear CPL signals ascribed to AICPL, whereas signals...

Perylene Bisimide In-chain Polyethylene with Unique Self-assembly Nanostructure through Acyclic Diene Metathesis (ADMET) Polymerization

A novel perylene tetracarboxylic acid bisimide (PTCBI) in-chain polyethylene (PE) was first prepared via acyclic diene metathesis (ADMET) polymerization of PTCBI-functionalized α,ω-diene monomer. The polymers could spontaneously self-assemble into hollow cylindrical structures in which the π-π interaction between adjacent PTCBI moieties was enhanced and the electron mobility was possibly promoted. The hydrogenation of as-obtained polymer was readily accomplished, affording the desired precision PTCBI in-chain PE with a saturated backbone, which showed high glass transition temperature (Tg = 63 °C), relatively wide range of light absorption (λ = 200−575 nm), and higher LUMO level (−3.62 eV). It can therefore serve as a superior model for facile construction of functional polyolefin and soluble PTCBI polymer with ordered architecture.

Sequential Modification of ADMET Polyketone via Oxime Chemistry and Electrophilic Alkoxyetherification

Post-polymerization modification is a facile and efficient method for the generation of diverse functional polymers. Herein, polymer-based molecular arrays were obtained by using sequential modification. First, periodic polyketone P0 was synthesized via acyclic diene metathesis (ADMET) polymerization of α,ω-diene M0. Oxime chemistry was employed in the functionalization of the ketone moieties of P0 using three commercially available alkoxyamine hydrochlorides. Finally, electrophilic alkoxyetherification, a four-component reaction, was employed in the modification of alkene groups on polymer main chains using N-bromosuccinimide (NBS), tetrahydrofuran, and fluorinated carboxylic acid. Complete conversion of reactive sites was observed in both steps, and the two modification reactions exhibited excellent compatibility. The thermal properties of the polymers as thermal stability, and glass transition and melting behaviours were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).

Linear, Y-shaped, and H-shaped amphiphilic azobenzene copolymers: Facile synthesis and topological effect on self-assembly and photoresponsive property

Novel linear (AB-type), Y-shaped (AB2-type), and H-shaped (B2AB2-type) amphiphilic block copolymers of poly(ethylene glycol) (PEG) with polymer containing azobenzene chromophores (PAzo) were successfully synthesized by the head-to-tail acyclic diene metathesis (ADMET) polymerization. Three types of acrylate functional ADMET chain stoppers were first prepared through the Michael addition reaction and esterification. Then, a series of amphiphilic copolymers were obtained via through ADMET polymerization of azobenzene-functionalized asymmetric α,ω-diene monomer using the as-prepared PEGs with acrylate end groups as macromolecular chain stoppers. Finally, the amphiphilic copolymers could spontaneously self-assemble into spherical nanoparticles in an aqueous medium. In view of the photoresponsive blocks of PAzo, the solution photochemical properties of the solution and the sizes of these spherical aggregates can be manipulated by changing the parameters such as UV and visible lights. The differences in structure of the copolymers induced profound effects on photoresponsive performance.

Highly Selective Olefin Metathesis with CAAC-Containing Ruthenium Benzylidenes

Several olefin metathesis reactions are studied, namely, jojoba oil oligomerization, methyl oleate self-metathesis, ring-closing metathesis (RCM) to form a nitrogen heterocycle, and 1,5-hexadiene acyclic diene metathesis polymerization (ADMET). The catalyst containing the Bertrand–Grubbs cyclic alkyl amino carbene (CAAC) ligand showed high selectivity by diminishing isomerization reactions; this was especially clear at high temperatures where the more widely used nitrogen heterocyclic carbene (NHC)-based catalysts show side reactions. Experimental and computational studies determined that it is much more difficult to produce ruthenium hydrides with CAAC, a property that can explain the improved observed activity. This finding opens a pathway for the development of even more selective olefin metathesis catalysts for reactions that require harsh conditions.

Synthesis of supramolecular precision polymers: Crystallization under conformational constraints

ABSTRACTPlacing artificial folding elements into precision polymers is an important strategy to systematically study structure formation in self‐assembly, particularly in the semicrystalline state. To this purpose, a series of precision polymers bearing either a N‐protected or N‐unprotected diaminopyridine (DAP) unit after every 16th, 18th, and 20th carbon as well as a urea unit after every 20th carbon along a polyethylene‐like polymer were synthesized via acyclic diene metathesis polymerization and subsequent hydrogenation. The polymers thus contain either H‐bonds (urea/DAP), π–π‐elements (DAP), or no H‐bonds (respective Nprotected urea/DAP‐units) in their main chain, able to consequently study the crystallization behavior under influence of such supramolecular moieties. Therefore, the thermal properties and crystallization behavior were analyzed via differential scanning calorimetry (DSC) as well as wide angle X‐ray diffraction. The obtained crystalline polymer is influenced by the different supramolecular interactions existing between adjacent polymer chains and the varying defect size exerted by the incorporated functional groups. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3736–3748

Periodically Grafted Linear–Hyperbranched Copolymers Based on Polyethylene and Polyglycidol: Importance of the Architecture on Properties

AbstractHere, the periodically grafted linear–hyperbranched copolymers (LHGCs) based on polyethylene (PE) and hyperbranched polyglycidol is synthesized via acyclic diene metathesis polymerization and anionic ring‐opening multibranching polymerization. The chemical composition of LHGCs can be controlled by changing the amount of the initial monomer. For the first time this allows to control the architecture (composition and sequence distribution), in which the run length between adjacent hyperbranched pendants is exact along PE backbone. By comparing with aperiodically grafted analogues, the results clearly show the composition and the sequence distribution of LHGCs is identified as the major factor to influence the thermal stability, crystallinity as well as hydrophilicity.

Synthesis of isohexide-di(ether-ene)s and ADMET polymerization

As fossil fuel reserves deplete and greenhouse gases increase, the scientific community is challenged to provide sustainable solutions. Sugar-based isohexides can be modified to prepare a library of isohexide-diene monomers for polymerization. Such isohexide-diene monomers can be subjected to acyclic diene metathesis (ADMET) polymerization to obtain green materials. This paper reports a single-step synthetic protocol to access a small family of isohexide-di(ether-ene)s and the corresponding polymers. The isohexide di(ether-ene)s could be isolated in good to excellent yields under optimized conditions. The resultant isohexide-di(ether-ene)s are potential versatile building blocks for pharmaceuticals and materials science. The synthetic utility of isohexide-di(ether-ene)s was demonstrated by subjecting them to ADMET polymerization using Grubbs first- and second-generation catalysts. The resultant viscous material was evaluated using proton nuclear magnetic resonance and matrix-assisted laser desorption/ionization time of flight mass spectroscopy, which suggest the formation of anticipated ADMET polymers. End-group analysis of the polymers revealed molecular weights of 800–13 800 g/mol. Slight improvement in the molecular weight was observed when benzoquinone was added or when the catalyst was added in two stages. Thus, the analysis of the poly(ether-ene)s suggests that low-molecular-weight polymers were formed under the optimized experimental conditions, and the molecular weight could not be improved beyond a point.

Inside Back Cover: Synthesis of Poly(arylene vinylene)s with Different End Groups by Combining Acyclic Diene Metathesis Polymerization with Wittig‐type Couplings (Angew. Chem. Int. Ed. 19/2017)

Inside Back Cover: Synthesis of Poly(arylene vinylene)s with Different End Groups by Combining Acyclic Diene Metathesis Polymerization with Wittig‐type Couplings (Angew. Chem. Int. Ed. 19/2017)

Synthesis of Poly(arylene vinylene)s with Different End Groups by Combining Acyclic Diene Metathesis Polymerization with Wittig-type Couplings.

A series of end-functionalized poly(9,9'-di-n-octylfluorene vinylene)s (EF-PFVs) with different end groups were obtained by 1) synthesizing EF-PFV with vinyl end groups by acyclic diene metathesis (ADMET) polymerization with a molybdenum catalyst and termination with an aldehyde and 2) subsequent olefin metathesis of the vinyl group with the molybdenum catalyst followed by Wittig-type coupling with another aldehyde. The exclusive formation of EF-PFVs containing a vinyl end group by the ADMET polymerization was confirmed by grafting PEG, and by the synthesis of amphiphilic triblock copolymers by combining atom transfer radical polymerization from the PFV chain end with PEG grafting through a click reaction. Various EF-PFVs with different end groups, such as C6 F5 , pyridyl, ferrocenyl, and terthiophene, have thus been prepared. Their fluorescence spectra (e.g., intensities, emission wavelengths) were influenced by the end groups and the length of the conjugation.

Synthesis of Poly(arylene vinylene)s with Different End Groups by Combining Acyclic Diene Metathesis Polymerization with Wittig‐type Couplings

AbstractA series of end‐functionalized poly(9,9′‐di‐n‐octylfluorene vinylene)s (EF‐PFVs) with different end groups were obtained by 1) synthesizing EF‐PFV with vinyl end groups by acyclic diene metathesis (ADMET) polymerization with a molybdenum catalyst and termination with an aldehyde and 2) subsequent olefin metathesis of the vinyl group with the molybdenum catalyst followed by Wittig‐type coupling with another aldehyde. The exclusive formation of EF‐PFVs containing a vinyl end group by the ADMET polymerization was confirmed by grafting PEG, and by the synthesis of amphiphilic triblock copolymers by combining atom transfer radical polymerization from the PFV chain end with PEG grafting through a click reaction. Various EF‐PFVs with different end groups, such as C6F5, pyridyl, ferrocenyl, and terthiophene, have thus been prepared. Their fluorescence spectra (e.g., intensities, emission wavelengths) were influenced by the end groups and the length of the conjugation.

Effects of End-Groups on Photophysical Properties of Poly(9,9-di-n-octylfluorene-2,7-vinylene)s Linked with Metalloporphyrins: Synthesis and Time-Resolved Fluorescence Spectroscopy

A series of poly(9,9-di-n-octyl-fluorene-2,7-vinylene)s (PFVs) containing metalloporphyrins at the chain ends with different conjugation lengths (ca. average 8 or 24 FV repeat units), PFV-[Por(M)]2, have been prepared by olefin metathesis of the vinyl chain ends in PFVs (prepared by acyclic diene metathesis polymerization by ruthenium–carbene catalysts) using molybdenum–alkylidene catalyst (reagent) followed by Wittig-type cleavage with formyl porphyrin containing different metal ions [Zn(II), Cu(II), Ni(II), and Pt(II)]. Effects of the metalloporphyrins on photophysical properties of PFVs were studied by means of time-resolved fluorescence spectroscopy. The fluorescence spectral profile from PFV moiety in all the polymers with end-porphyrins was almost identical to that of the reference PFV. However, fluorescence quantum yields were remarkably lower, depending upon the central metal ion and the chain length. The observed reduction of the quantum yields is ascribed to intramolecular energy transfer to the...

Joining Two Natural Motifs: Catechol-Containing Poly(phosphoester)s.

Numerous catechol-containing polymers, including biodegradable polymers, are currently heavily discussed for modern biomaterials. However, there is no report combining poly(phosphoester)s (PPEs) with catechols. Adhesive PPEs have been prepared via acyclic diene metathesis polymerization. A novel acetal-protected catechol phosphate monomer was homo- and copolymerized with phosphoester comonomers with molecular weights up to 42000 g/mol. Quantitative release of the catechols was achieved by careful hydrolysis of the acetal groups without backbone degradation. Degradation of the PPEs under basic conditions revealed complete and statistical degradation of the phosphotri- to phosphodiesters. In addition, a phosphodiester monomer with an adhesive P-OH group and no protective group chemistry was used to compare the binding to metal oxides with the multicatechol-PPEs. All PPEs can stabilize magnetite particles (NPs) in polar solvents, for example, methanol, due to the binding of the phosphoester groups in the backbone to the particles. ITC measurements reveal that multicatechol PPEs exhibit a higher binding affinity to magnetite NPs compared to PPEs bearing phosphodi- or phosphotriesters as repeating units. In addition, the catechol-containing PPEs were used to generate organo- and hydrogels by oxidative cross-linking, due to cohesive properties of catechol groups. This unique combination of two natural adhesive motives, catechols and phosphates, will allow the design of novel future gels for tissue engineering applications or novel degradable adhesives.

ADMET Polymerization: Greener Method for Synthesis of End-Functionalized Poly(Arylene Vinylene)s

Recent results for synthesis of conjugated polymers, poly(arylene vinylene)s exemplified as poly(fluorene vinylene)s and poly(phenylene vinylene)s, by acyclic diene metathesis (ADMET) polymerization have been introduced. The methods using molybdenum and ruthenium catalysts afforded defect-free, high molecular weight polymers with all trans olefinic double bonds, and significant reduction of by-products (halogen, sulfur etc.) in addition of decrease of structurally defects have been attained. The methods also demonstrated precise synthesis of end-functionalized polymers that showed unique optical properties combined with the end groups. Catalytic one-pot syntheses of end-functionalized poly(9,9-dialkylfluorene-2,7-vinylene)s have been attained by both ruthenium (by chain-transfer) and molybdenum catalysts and the method should provide more green route for synthesis of conjugated materials with better device performance.

ADMET polymerization of α,ω-unsaturated glycolipids: synthesis and physico-chemical properties of the resulting polymers

Trehalose diesters exhibiting α,ω-unsaturation are glycolipids which can be easily polymerized by ADMET (acyclic diene metathesis) polymerization.

Macrocycle-based topological azo-polymers: facile synthesis and unusual photoresponsive properties

Macrocycle-based topological azo-polymers with unusual photosensitive properties were synthesized via a selective acyclic diene metathesis polymerization of different monomers using an acrylate-functionalized cyclic azo-polymer as a chain stopper prepared from a linear precursor by “click” cyclization reaction, which will open a new perspective in photoinduced materials.

Photoresponsive Polymeric Reversible Nanoparticles via Self-Assembly of Reactive ABA Triblock Copolymers and Their Transformation to Permanent Nanostructures.

Azobenzene-functionalized ABA triblock copolymers with controlled molecular weights are prepared first via a sequential ring-opening metathesis polymerization and acyclic diene metathesis polymerization in one-pot, which are readily converted, by a facile esterification, to the modified ABA triblock copolymers. Then, these reactive triblock copolymers can spontaneously self-assemble in a selective solvent to form reproducible and reversible polymeric core-shell nanoparticles. Finally, the stable and permanent shell-crosslinked nanoparticles are obtained by an intramolecular crosslinking reaction in dilute solution under UV light irradiation. These as-prepared polymeric nanoparticles and their precursor incorporating azobenzene chromophores exhibit distinct photoresponsive performance and morphological variation.