Well phase separated segmented copolymers via acyclic diene metathesis (ADMET) polymerization

Segmented oligomers consisting of polyoctenylene hard segments and unsaturated polytetrahydrofuran soft segments were prepared using acyclic diene metathesis (ADMET) copolymerization techniques. These are the first such segmented materials prepared via metathesis chemistry. Two different molecular weight α,ω-poly(tetrahydrofuran)diene soft segment monomers of the structure [CH₂CH(CH₂)₄[O(CH₂)₄]-_nO(CH₂)₄CHCH₂] (1) were synthesized by the cationic living polymerization of tetrahydrofuran (THF). Trifluoromethanesulfonic anhydride, (CF₃SO₂)₂O (triflic anhydride) (2), was employed as the initiator, followed by in situ bis-functionalization with 5-hexen-1-ol, [CH₂=CH(CH₂)₄OH] (3), to yield soft segment dienes with vinyl end groups. The functionality of these soft segment monomers was approximately 1.9. These telechelic monomers possessed sufficient functionality to be homopolymerized or copolymerized with 1,9-decadiene (4) to generate well phase separated, segmented oligomers exhibiting hard segment/soft segment thermal behavior. The segmented copolymers were characterized by ¹H-NMR, ¹³C-NMR, and IR spectroscopy, elemental analysis, and TGA and DSC analysis. Average molecular weights were determined by gel permeation chromatography (GPC) and end-group analysis. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3441–3449, 1997     

Triptycene‐containing polyetherolefins via acyclic diene metathesis polymerization

Several new triptycene‐containing polyetherolefins were synthesized via acyclic diene metathesis (ADMET) polymerization. The well‐established mechanism, high selectivity and specificity, mild reaction conditions, and well‐defined end‐groups make the ADMET polymerization a good choice for studying systematic variations in polymer structure. Two types of triptycene‐based monomer with varying connectivities were used in the synthesis of homopolymers, block copolymers, and random copolymers. In this way, the influence of the triptycene architecture and concentration in the polymer backbone on the thermal behavior of the polymers was studied. Inclusion of increasing amounts of triptycene were found to increase the glass transition temperature, from ?44 °C in polyoctenamer to 59 °C in one of the hydrogenated triptycene homopolymers ( H‐PT2 ). Varying the amounts and orientations of triptycene was found to increase the stiffness ( H‐PT1 ), toughness ( PT1₁‐b‐PO₁ ) and ductility ( PT1₁‐ran‐PO₃ ) of the polymer at room temperature. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Long‐chain branched random polyethylene via acyclic diene metathesis (ADMET) copolymerization

Five types of ethylene/α‐alkene model copolymers containing 21‐carbon alkyl branches have been synthesized via acyclic diene metathesis (ADMET) copolymerization. The overall branch content is controlled by varying the feedstock ratio of the long‐chain branched symmetrical α, ω‐diene and 1,9‐decadiene. Well‐defined melting transitions are present at low branch incorporation, followed by the broadening of the endotherms as the branch contents increase. However, instead of making the material amorphous, further increasing of the branch contents leads to the retrieval of the semi‐crystalline material creating a new crystalline domain, branches that co‐crystallize. Detailed IR spectra analyses suggest a crystal morphology transformation from orthorhombic to hexagonal phase as the branch content increases in these polymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018     

Ferrocene-containing polymers synthesized by acyclic diene metathesis (ADMET) polymerization

Herein we reported that ferrocene-containing polymers could be synthesized via acyclic diene metathesis(ADMET) polymerization of ferrocene-containing bis-styryl monomers. The all-trans-configured vinylene bonds of stilbene segment were proven by means of 13C-NMR, 1H-NMR, MALDI-TOF mass spectrometry and FTIR. Poly(1) showed maxima for absorption at 320 nm and emission at 430 nm which are structurally very similar to trans-stilbene, but 24 and 16 nm red shifted respectively. CIE chromaticity diagram shows that emission color could be adjusted by controlling the molecular weight. The polymer showed excellent solubility in common organic solvents and good thermal stability evidenced by TGA and DSC. The results of CV suggested the polymer possessed noninteracting metal centers which was confirmed by a reversible one-electron redox wave observed for the polymer.     

One-pot synthesis of polyrotaxanes via acyclic diene metathesis polymerization of supramolecular monomers

A one-pot synthesis of polyrotaxanes has been developed. The method employs a supramolecular monomer comprising a polymerizable ammonium salt and crown ether, in combination with dynamic ADMet polymerization. Ultimately, highly efficient complexation, polymerization, and end-capping were accomplished in a single operation to yield polyrotaxanes with M(w) up to 19.3 kDa and >80% of the repeat units being complexed.     

Regio-regular and cross-conjugated poly(thienylene vinylene)s through acyclic diene metathesis

Poly(thienylene vinylene)s (PTV's) are early examples of conjugated polymers but have not been extensively studied when compared with closely analogous polythiophenes. PTV's synthesized through previously reported techniques are similar in structures that contain various alkyl or alkoxy side-chains that exert limited impact on the polymer electronic properties. Herein, we report the preparation of a series of regio-regular PTV's (rr-PTV's) bearing cross-conjugated side-chains through ADMET polymerization of a common brominated di(thienylene vinylene) (DTV) monomer followed by PPM reactions on the resulting brominated PTV. These new polymers contain a bulky silyloxy alkyl side-chain and a functionalized thiophene moiety on every main-chain thiophene unit, and their regio-regular placement is confirmed by NMR spectroscopy. The thienyl based side-groups broaden polymer absorption ranges and at the same time lead to uncommon emission properties that are results of light-induced charge transfer events between the polymer main-chains and side-chains. Removal of the silyl groups on one of these rr-PTV's led to insoluble materials and x-ray diffraction experiments on the collected solids displayed distinct scattering peaks that are absent from similarly functionalized regio-random PTV's reported previously, thus suggesting better crystallinity originated from regio-regularity.     

Fatty acid derived phosphorus‐containing polyesters via acyclic diene metathesis polymerization

The acyclic diene metathesis (ADMET) polymerization of a phosphorus‐containing α,ω‐diene prepared from a plant oil derived building block is reported. Different ruthenium based metathesis catalysts and conditions were tested to optimize the ADMET polymerization of this monomer. Undecylenyl undecenoate was used as fully renewable comonomer to obtain polyesters with different phosphorus contents and to increase the renewable content of the final polymers. Copolymerization caused marked variations in the molecular weights leading to polyesters from 6 to 38 KDa. The effect of the ADMET polymerization temperature in the thermal properties of the copolymers was studied and their thermal degradation and flame retardant properties were evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5760–5771, 2009     

Ring-opening metathesis polymerization (ROMP) of isomerically pure functional monomers and acyclic diene metathesis depolymerization (retro-ADMET) of functionalized polyalkenamers

ROMP and retro-acyclic diene metathesis (ADMET) were used for the synthesis of new functional polymers and functional oligomers, respectively. Purely exo and enantiomerically pure norbornene and 7-oxanorbornene derivatives were prepared using stereospecific synthesis, effective fractionation and high yield condensation reactions. Successful ROMPs of those monomers were performed using either the new carbenic Schrock’s or Grubb’s catalysts or in some cases a classical bicomponent catalyst. New functional polymers such as optically active poly(norbornene-2-carboxylic acid), reactive poly(norbornene-2-azlactone), and side-chain liquid crystal polyoxanorbornenes were fully characterized. On the other hand, successful depolymerizations of 1,4-polyisoprene and of epoxidized 1,4-polybutadiene via cross-metathesis with 4-octene were performed using a stabilized bicomponent catalyst and the Grubb’s catalyst, respectively. Conditions for the controlled synthesis of epoxidized oligobutadienes and of epoxydienic monomers via retro-ADMET were clearly defined.     

Arylene ethynylene macrocycles prepared by precipitation-driven alkyne metathesis

A convenient, multigram-scale synthesis of arylene ethynylene macrocycles near room temperature is described. Driven by the precipitation of a diarylacetylene byproduct, alkyne metathesis produces the desired macrocycles in one step from monomers in high yields.     

Formation of macrocycles via ring-closing olefin metathesis

The enhanced metathesis activity of 1,3-dimesityl-4,5-dihydroimidazole-2-ylidene ruthenium carbene catalyst 3 significantly increases the feasibility of synthesizing macrocyclic compounds. Catalyst 3 exhibits sufficient activity in RCM to dimerize alpha,beta-unsaturated ester substrates and afford the corresponding head-to-tail (E,E)-dimeric (and trimeric) macrocycles. The dimerization appears to be under thermodynamic control with the product mixture dependent not only on the electronic and steric nature of the substrate but also on concentration.     

Rapid construction of shape-persistent H-bonded macrocycles via one-pot H-bonding-assisted macrocyclization

The study of macrocycles has crossed many traditional disciplines such as chemistry, physics, biology, medicine and engineering with many research areas concentrating on specific and selective molecular recognition, self-organisation and its already demonstrated and other promising applications. Compared to traditional strategies to synthesize macrocycles with widely ranging structures using such as templated cyclization or dynamic covalent bond formation, one-pot H-bonding-assisted macrocyclization has been shown to provide a simple, fast and cost-efficient method to synthesize shape-persistent H-bonded macrocycles of varying types containing an internal cavity of as large as 2.9 nm in diameter. This review will summarize the recent works on such “greener” syntheses of H-bonded macrocycles that help to create a whole new dimension of research and to offer a new bottom-up strategy for constructing functional architectures and materials.     

Graft copolymers by acyclic diene metathesis and atom transfer radical polymerization techniques

Precise graft copolymer architectures were achieved by combining the macromonomer technique with the acyclic diene metathesis (ADMET) reaction. These well‐defined copolymer structures were the result of proper monomer design before metathesis polymerization. Features such as length of the graft, nature, and concentration of the graft site along the backbone were manipulated via the combination of living atom transfer radical polymerization methods with ADMET chemistry. Furthermore, the physical behavior of these materials was altered such that they presented dissimilar thermal properties of either the homopolymers or random copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2816–2827, 2003     

Hyperbranched polyphosphoesters with reactive end groups synthesized via acyclic diene metathesis polymerization and their transformation to crosslinked nanoparticles

A novel hyperbranched polyphosphoester (HBPPE) was prepared by acyclic diene metathesis (ADMET) polymerization of an AB₂ monomer using the second‐generation Hoveyda–Grubbs catalyst. IR analysis, gel permeation chromatography with multiangle laser light scattering, and NMR spectroscopy confirmed their controlled synthesis. The effect of the ADMET polymerization time in the thermal properties of HBPPEs was studied and their thermal degradation and flame‐retardant properties were evaluated. These reactive HBPPEs were used to synthesize polyphosphoesters nanoparticles by intramolecular crosslinking of the end acrylate groups in dilute solution. The successful preparation of this new type of polymer nanoparticles was proven by NMR spectroscopy and gel permeation chromatography. The morphologies of nanostructures were investigated via dynamic light scattering, atom force microscopy, and transmission electron microscopy. The results revealed that the crosslinked nanoparticles, which have a comparatively uniform size, were stable and reproducible in organic solvents. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4331–4340     

Potent thrombin inhibitors via a 20-membered ring olefin metathesis macrocyclization

Twenty-membered ring pyrazinone derived macrocycles were prepared as a means to enhance the potency of existing thrombin inhibitors. Macrocyclization was accomplished via Grubbs olefin metathesis of a highly functionalized allyl-alloc scaffold, thus further confirming the power of such methodology.     

Post‐functionalization of perfluorophenyl ester‐functional acyclic diene metathesis polymer

The acyclic diene metathesis (ADMET) polymerization was utilized for the design of the ADMET polymer (M_n = 21,200 g/mol, M_w/M_n = 1.74) with pendant perfluorophenyl ester functionality using Grubbs first generation catalysis overnight in bulk at 80 °C. Next, a wide variety of functional groups, like benzyl, octyl, propargyl, allyl, and furfuryl was quantitatively incorporated to the ADMET polymer backbone through various amines using activated ester substitution reaction. The ADMET polymers studied in this work were characterized using ¹H, ¹³C, and ¹⁹F NMR, GPC and DSC and displayed a monomodal distribution and a rather broad polydispersity index in the range of ?1.33 to 1.90. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2593–2598     

Synthesis of resorcinylic macrocycles related to radicicol via ring-closing metathesis

Novel resorcinylic macrolides, for example, 17, 24, were prepared via ring-closing metathesis as analogues of the HSP90 inhibitor radicicol.     

Reaction pathways leading to arylene ethynylene macrocycles via alkyne metathesis

Mechanistic studies on the direct formation of arylene ethynylene macrocycles via alkyne metathesis catalyzed by a molybdenum complex are reported. Gel permeation chromatography (GPC) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry on the products from metathesis of monomer 1 show the initial formation of linear oligomers and large macrocycles (n > 6), followed by their transformation into the thermodynamically most stable product distribution-mainly the cyclic hexamer. Variable temperature and scrambling experiments reveal the reversibility of macrocycle formation. Nearly identical product distributions are observed from the cross metathesis of hexacycle 2 with diphenylacetylene and from the metathesis of bis(phenylethynyl) substituted monomer 4, demonstrating that macrocycle formation is thermodynamically rather than kinetically controlled. The metathesis byproduct, 3-hexyne, is shown to inhibit the catalyst. It is suggested that the relative metathesis rates of dialkylalkynes versus diarylalkynes trap the catalyst in a nonproductive manifold, rendering it unavailable for the productive metathesis of aryl alkylalkyne substrates. This finding indicates that dialkyl-substituted alkyne byproducts should be avoided (or efficiently removed) if the metatheses of aryl substrates, especially those with electron-withdrawing groups, are to proceed to high conversion.     

Acyclic diene metathesis (ADMET) depolymerization of functionalized furan-based polymers

Acyclic dience metathesis (ADMET) depolymerization of functionalized furan-based polymers prepared via aqueous ring-opening polymerization of 7-oxanobornenes has been investigated. Results indicate that while very high molecular weight poly [exo-N-methyl-7-oxabicyclo [2.2.1] hept-2,5-diene-2,3-dicarboximide] can be depolymerized to oligomers with ease, poly [2,3-dicarbomethoxy-7-oxabicyclo [2.2.1] hept-2,5-diene] is more resistant to depolymerization under similar conditions. This difference may be due to differential interaction of the carbonyls in the side chains with the metal atom of the catalyst in the proposed metallacyclobutane intermediate. ADMET depolymerization of poly [2,3-bis (trifluoromethyl)-7-oxabicyclo [2.2.1] hept-2,5-diene] was feasible, however, the extent of depolymerization was decreased due to the use of a coordinating solvent (THF) used during the depolymerization process. © 1994 John Wiley & Sons, Inc.