Acyclic Diene Research Articles

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.

Tailoring Pore Size and Chemical Interior of near 1 nm Sized Pores in a Nanoporous Polymer Based on a Discotic Liquid Crystal.

A triazine based disc shaped molecule with two hydrolyzable units, imine and ester groups, was polymerized via acyclic diene metathesis in the columnar hexagonal (Colhex) LC phase. Fabrication of a cationic nanoporous polymer (pore diameter ∼1.3 nm) lined with ammonium groups at the pore surface was achieved by hydrolysis of the imine linkage. Size selective aldehyde uptake by the cationic porous polymer was demonstrated. The anilinium groups in the pores were converted to azide as well as phenyl groups by further chemical treatment, leading to porous polymers with neutral functional groups in the pores. The pores were enlarged by further hydrolysis of the ester groups to create ∼2.6 nm pores lined with −COONa surface groups. The same pores could be obtained in a single step without first hydrolyzing the imine linkage. XRD studies demonstrated that the Colhex order of the monomer was preserved after polymerization as well as in both the nanoporous polymers. The porous anionic polymer lined with −COOH groups was further converted to the −COOLi, −COONa, −COOK, −COOCs, and −COONH4 salts. The porous polymer lined with −COONa groups selectively adsorbs a cationic dye, methylene blue, over an anionic dye.

Synthesis of Poly(vitamin C) through ADMET.

l-Ascorbic acid, commonly known as vitamin C and one of the most important biological compounds, is converted to a α,ω-diene monomer and subsequently polymerized for the first time by acyclic diene metathesis. Various experimental conditions such as polymerization medium, catalyst type, temperature, and monomer/catalyst ratio are studied. The moderate molecular weight polymers are achieved when the polymerizations are conducted under bulk conditions employing the Grubbs first generation (G1) or Hoveyda-Grubbs second generation catalyst (HG-2). In the solution case, on the other hand, low molecular weight polymers are obtained regardless of the catalyst type. Moreover, when the catalyst performances are compared, it is found that G1 produces the higher molecular weight as well as higher yield polymers with respect to the HG-2.

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.

Formation of TbPc2 Single-Molecule Magnets' Covalent 1D Structures via Acyclic Diene Metathesis.

We present here a reaction scheme to connect TbPc2 single-molecule magnets into 1D architectures using acyclic diene metathesis. To investigate the impact of the bonding through aliphatic chains on the magnetic properties of TbPc2, we isolate and characterize the dimeric species obtained as one of the products of the reaction. Remarkably, the magnetic properties are only slightly modified after the formation of the bond between molecules, enlightening the great potential of this reaction scheme.

Degradable fluorescent single-chain nanoparticles based on metathesis polymers.

We introduce the facile synthesis of fluorescent single-chain nanoparticles (SCNPs) based on chain-shattering acyclic diene metathesis (ADMET) polymers featuring self-immolative azobenzene motifs. An electrophilic alkoxyetherification is utilized to introduce the photoreactive moieties required for the subsequent chain collapse via UV-induced nitrile imine-mediated tetrazole-ene cycloaddition (NITEC).

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.

Triazolinedione-“clicked” poly(phosphoester)s: systematic adjustment of thermal properties

The thermal properties of halogen-free flame retardant poly(phosphoester)s from acyclic diene metathesis polycondensation have been optimized by a systematic post-modification using 1,2,4-triazoline-3,5-dione derivatives.

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.

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.

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.

Thermally Degradable Polyesters with Tunable Degradation Temperatures via Postpolymerization Modification and Intramolecular Cyclization

We report the novel synthesis of thermally degradable polyesters through the postpolymerization modification of an unsaturated aliphatic polyester from maleic acid via Michael addition reaction with β-amino mercaptans. A high molecular weight polyester (P0) was synthesized by the acyclic diene metathesis (ADMET) polymerization of a diene monomer, di(10-undecenyl) maleate. Postpolymerization modification of P0 with three β-amino mercaptans (2-aminoethanethiol, l-cysteine methyl ester, and 2-(butylamino)ethanethiol) and 2-mercaptoethanol via the selective and quantitative thiol–Michael addition reaction with the maleate vinylic double bonds afforded four polyesters (P1–P4). All the polyesters were characterized by 1H NMR, GPC, and MALDI-TOF-MS, and their thermal properties were studied by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The three polymers with pendant amino groups (P1–P3) subjected to thermal-induced degradation in the solid state, the driving force of which i...

Polyethylene containing aliphatic ring and aromatic ring defects in the main chain: Synthesis via ADMET and comparisons of thermal properties and crystalline structure

Three polyethylene containing different non-planar aliphatic ring ether units (1,4-cyclohexylenedioxy, 4,4′-bicyclohexylenedioxy and 4,4′-isopropylidenedicyclohexylenedioxy) were synthesized via acyclic diene metathesis polymerization (ADMET) and subsequent hydrogenation. They were compared with their counterpart polymers containing aromatic ring defects in aspects of chain structural, thermal properties and crystalline structure by investigations with 1H NMR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). Regardless of the trans/cis isomers of cyclohexane moieties in these polymers, the results demonstrated that polyethylene containing non-planar aliphatic ring units showed decreased thermal stability as compared with the corresponding PE containing aromatic ring defects. Moreover, study on crystallization behaviors indicated that in contrast to their aromatic counterparts, introduction of the non-planar aliphatic defects perturbed the corresponding crystal structure more intensively, and larger space is needed to include these defects in the solid phase. As a result, their WAXD reflections shifted to lower scattering angles that correspond to increased d-spacing, and the polymers exhibited lower melting points. SAXS results proved that non-planar aliphatic ring defects result in increased dimension of amorphous region. Calculated by melting points and enthalpy, these polymers had smaller crystalline lamella thickness and lower crystallinity than their aromatic counterparts.

Electron Transfer Studies on Conjugated Ferrocenyl-Containing Oligomers

1,2-Divinylferrocene (1) and 1,2-diformylferrocene (3) have been converted to ferrocenyl-containing oligomers in good yields using ADMET (acyclic diene metathesis) and HWE (Horner–Wadsworth–Emmons) reaction protocols. The resulting oligomers showed a high uniformity (low dispersity values); however, the poor solubility limits the chain growth and led to low average molecular weights. Within electrochemical measurements (CV) the conjugated materials showed reversible behavior that was stable during multicyclic experiments. Coupled electrochemical and spectroscopic studies confirmed electron transfer interactions between the ferrocenyl units through the oligomeric chains.

Poly(phosphorodiamidate)s by Olefin Metathesis Polymerization with Precise Degradation.

Degradable polymers are a currently growing field of research for biomedical and materials science applications. The majority of such compounds are based on polyesters and polyamides. In contrast, their phosphorus-containing counterparts are much less studied, in spite of their potential precise degradation profile and biocompatibility. Herein, the first library of poly(phosphorodiamidate)s (PPDAs) with two P-N bonds forming the polymer backbone and a pendant P-OR group is prepared through acyclic diene metathesis polymerization. They are designed to vary in their hydrophilicity and are compared with the structural analogues poly(phosphoester)s (PPEs) with respect to their thermal properties and degradation profiles. The degradation of PPDAs can be controlled precisely by the pH: under acidic conditions the P-N linkages in the polymer backbone are cleaved, whereas under basic conditions the pendant ester is cleaved selectively and almost no backbone degradation occurs. The PPDAs exhibit distinctively higher thermal stability (from thermogravimetric analysis (TGA)) and higher glass transition and/or melting temperatures (from differential scanning calorimetry (DSC)) compared with analogous PPEs. This renders this exotic class of phosphorus-containing polymers as highly promising for the development of future drug carriers or tissue engineering scaffolds.

Synthesis of Unsaturated Nonionic Poly(ester‐sulfones) via Acyclic Diene Metathesis (ADMET) Polymerization and Anode‐Selective Electrophoretic Deposition

Nonionic aliphatic polymers containing ester and sulfonyl moieties, [poly(ester‐sulfones)s] were found to undergo anode‐selective electrophoresis under electrophoretic deposition conditions. Herein are reported the syntheses of unsaturated nonionic polyesters containing sulfide linkages and double bonds on the polymer backbone via acyclic diene metathesis polymerization using a Grubbs' catalyst. Subsequent oxone oxidation was carried out, affording the corresponding poly(ester‐sulfone), followed by electrophoretic deposition of the unsaturated poly(ester‐sulfone) onto stainless steel. Subsequent UV‐irradiation cured the deposited film, improving the peeling strength of the coating. image