Ring-opening metathesis polymerization of 9-phenyl-1,5-cyclododecadiene

Synthesis of butadiene-based sequence-controlled copolymers that are composed of commercial monomers such as styrene, butadiene, and ethylene was investigated. New substituted cyclododecadiene derivatives, 9-phenyl-1,5-cyclododecadiene was synthesized by reductive-phenylation method from 1,5-cyclododecadiene-9-one and was polymerized with tungsten-based catalyst systems to obtain a microstructure-controlled terpolymer. A sequence-controlled 2 : 1 : 1 terpolymer of butadiene, styrene and ethylene was successfully synthesized. The glass transition of the terpolymer occurred at ?33.6°C. © 1995 John Wiley & Sons, Inc.     

Ring-opening metathesis polymerization (ROMP) of fullerene-containing monomers in the presence of a first-generation Grubbs catalyst

New norbornene-type monomers containing covalently bound C60 fullerene have been obtained. In the presence of the 1st generation Grubbs catalyst [(PCy₃)₂Cl₂RuCHPh] (Cy is cyclohexyl), these monomers smoothly undergo homopolymerization and copolymerization with parent fullerene-free monomers. The homopolymers are insoluble in common organic solvents, while the copolymers obtained at different molar ratios to their fullerene-free analogues are very soluble in organic solvents and can be suitable for the preparation of thin films.     

Ring-opening metathesis polymerization of cis-5-norbornene-endo-2,3-dicarboxylic anhydride derivatives using the grubbs third generation catalyst

A series of cis-5-norbornene-endo-2,3-dicarboxylic anhydride(NDCA,M1) derivatives(M2-M4) with different types of nonpolar substituted groups were synthesized and characterized by ~1H/~(13)C-NMR and mass spectrometry(MS). Ringopening metathesis polymerization(ROMP) of these monomers using the Grubbs third generation catalyst(G3) generated high molecular weight polymers with much improved solubility compared with the NDCA's homopolymer. It was found that the solubility of these polymers increased with increased substituent's steric hindrance. The living polymerization of NDCA derivative containing the bulkiest substituent(M4) catalyzed by G3 in tetrahydrofuran was confirmed by the kinetic studies with low polydispersity indices(PDI)( 1.30). By using sequential ROMP, well-defined diblock copolymers containing anhydride groups were synthesized.     

Ring-opening polymerization of cyclic carbonates by alcohol–acid catalyst

Ring-opening reactions of 1,3-dioxepan-2-one ( 1 ) and 1,3-dioxan- 2 -one (2) with several alcohols were examined. The reactions proceeded without trifluoroacetic acid (TFA) in low conversions, while they proceeded smoothly with TFA to afford the ring-opened adducts and oligomers. Ring-opening polymerizations of 1 and 2 were also carried out by alcohol–acid catalysts to afford the corresponding polycarbonates (M _n = 2500−6800). The molecular weights increased with increase of the conversions of 1 and 2. The observed polymerization rates of 1 and 2 were determined as 24.4 × 10⁻⁶ and 0.8 × 10⁻⁶ s⁻¹, respectively. Mechanistic aspects were studied by NMR spectroscopy. The methylene protons α and β to the carbonate moieties shifted to lower fields in 0.06–0.11 ppm in the ¹H-NMR spectra by the addition of TFA. Downfield shifts of the carbonyl carbon signals of 1 and 2 were observed in 3.94–4.15 ppm in the ¹³C-NMR spectra. These results strongly suggest that the cyclic carbonates are activated by TFA. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2463–2471, 1998     

Ring-opening metathesis polymerization for the preparation of norbornene-based weak cation-exchange monolithic capillary columns

Functionalized monolithic columns were prepared via ring-opening metathesis polymerization (ROMP) within silanized fused silica capillaries with an internal diameter of 200 μm by in situ grafting. This procedure is conducted in two steps, the first of which is the formation of the basic monolithic structure by polymerization of norborn-2-ene (NBE) and 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo,endo-dimethanonaphthalene (DMN-H6) in a porogenic system (toluene and 2-propanol) using RuCl₂(PCy₃)₂(CHPh) as ROMP initiator. In the second step the still active initiator sites located on the surface of the structure-forming microglobules were used as receptor groups for the attachment (“grafting”) of functional groups onto the monolithic backbone by flushing the monolith with 7-oxanorborn-2-ene-5,6-carboxylic anhydride (ONDCA). Functionalization conditions were first defined that did not damage the backbone of low polymer content (20%) monoliths allowing high-throughput chromatographic separations. Variation of the functionalization conditions was then shown to provide a means of controlling the degree of functionalization and resulting ion-exchange capacity. The maximum level of in situ ONDCA grafting was obtained by a 3 h polymerization in toluene at 40 °C. The weak cation-exchange monoliths obtained provided good separation of a standard peptide mixture comprising four synthetic peptides designed specifically for the evaluation of cation-exchange columns. An equivalent separation was also achieved using the lowest capacity column studied, indicative of a high degree of robustness of the functionalization procedure. As well as demonstrably bearing ionic functional groups enabling analyte separation in the cation-exchange mode, the columns exhibited additional hydrophobic characteristics which influenced the separation process. The functionalized monoliths thus represent useful tools for mixed-mode separations.     

In situ catalyst systems for ring-opening metathesis polymerization

Several new in situ tungsten catalyst systems for ring-opening metathesis polymerizations (ROMP) by reaction injection molding (RIM) have been developed by adding BF₃ promoter to binary catalyst systems, by using metal hydride cocatalysts, and by altering the ligands on the procatalyst metal center. BF₃ etherates improved catalyst efficiency and reduced induction times for formation of active catalysts from reaction of aryloxytungsten complexes [e.g., (ArO)_y(WX_x)] with organotin hydrides. Coordinatively unsaturated cationic intermediates, such as [(ArO)_yWX_x-1]⁺ BF₃X⁻, are proposed to facilitate formation of the active catalysts. Tougher poly(dicyclopentadiene) (polyDCPD) composites were produced using < 5 wt % of styrene-butadiene block copolymers due to formation of small “shell-core” rubber morphologies when BF₃ promoter was added to the catalyst system. Nonalkylating metal hydrides besides R₃SnH, including (PPh₃)₂CuBH₄, (PPh₃CuH)₆, and Cp₂ZrClH, were shown to be cocatalysts. The optimum 2 : 1 stoichiometric ratio of organotin hydride cocatalyst to tungsten, revealed by BF₃-promoted catalyst systems, and W^V EPR resonances (g ∼ 1.7) observed in the reaction of aryloxytungsten with organotin hydride are consistent with an overall reduction and reoxidation mechanism for formation of the active metathesis catalysts. Some tungsten complexes derived from 9-hydroxyfluorene, 2,2′-(and 4,4′)-biphenols, and 1,4-hydroquinones were found to be very reactive procatalysts, even in the absence of cocatalyst in some cases. These procatalysts also were paramagnetic, characterized by unusual EPR spectra consistent with W^V (g = 1.6–1.9) and “ligand-centered” (g = 2.003) resonances. Valence tautomeric species, analogous to catecholate-semiquinonate complexes, are proposed. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3027–3047, 1997     

Ring-opening metathesis polymerization (ROMP) of N-cycloalkyl-7-oxanorbornene dicarboximides by well-defined ruthenium initiators

Ring-opening metathesis polymerization (ROMP) of exo-N-(1-adamantyl)-7-oxanorbornene-5,6-dicarboximide (AdONDI) (3a), exo-N-cyclohexyl-7-oxanorbornene-5,6-dicarboximide (ChONDI) (3b) and exo-N-phenyl-7-oxanorbornene-5,6-dicarboximide (PhONDI) (3c) using well-defined alkylidene ruthenium catalysts (PCy₃)₂(CI)₂RuCHPh (I) and (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) (PCy₃)CI₂RuCHPh (II) was studied. The catalysts I and II gave polymers with around 70% and 50% trans vinylene content, respectively. The homopolymer of 3a had a T_g of 198 °C, while poly-3b showed a T_g of 122 °C. Copolymers of 3a, 3b and 3c with norbornene (NB) showed significant T_g increases over poly-NB.     

Ring-opening metathesis polymerization with [2+2]-crosslinking to create new materials

There are almost no examples of Grubbs’-type ring-opening metathesis polymers that have been [2+2]-crosslinked. Two new monomers, 6 and 10, were used to construct two novel linear soluble polymers 7 and 11, bearing photochemically labile moieties for [2+2]-cycloaddition reactions. These soft polymers were photocrosslinked into very hard polymers, 8 and 12. Potential advantages of these new bioinspired materials include: (1) ready processing into flat, round, and cylindrical shapes; (2) reasonably low toxicity due to trace amounts of catalyst needed; and (3) rapid rate of polymerization and crosslinking that avoids acids and bases.     

Ring-opening metathesis polymerization of norbornene and norbornadiene by tungsten(II) and molybdenum(II) complexes

The reaction of norbornene (NBE) and norbornadiene (NBD) in the presence of seven-coordinate tungsten(II) and molybdenum(II) complexes of the [(CO)₄M(μ-Cl)₃M(SnCl₃)(CO)₃] and [MCl(M′Cl₃)(CO)₃(NCMe)₂] (M=W, Mo; M′=Sn, Ge) types leads to ring-opening metathesis polymerization (ROMP) and to the formation of high molecular weight polymers. The geometric structure of these polymers was determined by means of ¹H- and ¹³C-NMR spectroscopy. The monitoring of the reaction between cyclic olefins and the metal complex by means of ¹H-NMR spectroscopy allowed us to observe the coordination of NBD to metal atoms in the initiation step of the polymerization process. Compounds of the [MCl(SnCl₃)(CO)₃(η⁴-NBD)] type prepared directly from [(CO)₄M(μ-Cl)₃M(SnCl₃)(CO)₃] or [MCl(M′Cl₃)(CO)₃(NCMe)₂] (M=W, Mo) in the presence of an excess of NBD initiate the ROMP reaction immediately. The detection of the first-formed products in the reaction between the metal complex and cyclic olefins provides valuable information concerning the nature of the initiating species.     

Covalent crosslinking of 1-D photonic crystals of microporous Si by hydrosilylation and ring-opening metathesis polymerization

Free-standing porous Si multilayer dielectric mirrors, prepared by electrochemical etching of crystalline Si, are treated with a ruthenium ring-opening metathesis polymerization (ROMP) catalyst followed by norbornene to produce flexible, stable composite materials in which poly(norbornene) is covalently attached to the porous Si matrix.     

Ring‐opening metathesis polymerization of a modified linseed oil with varying levels of crosslinking

A commercial norbornyl‐functionalized linseed oil, blended with a bicyclic norbornene‐based crosslinking agent (at loadings ranging from 0 to 50 wt %) undergoes ring‐opening metathesis polymerization with the 1st generation Grubbs' catalyst to form a biorenewable polymer network. Comonomers are characterized, the thermal and mechanical properties of the cured systems are investigated by dynamic mechanical analysis, and thermal decomposition is evaluated by thermogravimetric analysis. The resin is shown to consist of a modified linseed oil and small oligomers of cyclopentadiene. Broad tan δ peaks suggest inhomogeneous phase morphologies, which result in complex crosslinking behaviors. The thermal stability of the polymers increases with increasing crosslinker content. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6851–6860, 2008     

Methods for removal of residual catalyst from polymers prepared by ring opening metathesis polymerization

Methods for removing the residual Grubbs' third generation catalyst from polymers prepared by ring opening metathesis polymerization are reported. Two strategies were investigated for reduction of the residual catalyst in the final polymer product. The first strategy involved the use of heterogeneous functionalized particles to scavenge the catalyst from the solution. Filtration of the particles followed by precipitation produced polymers with 10–60 ppm residual catalyst, depending on the type of particle used, surface functional groups, and number of equivalents. The second strategy used small organic molecules that could coordinate to the metal species and modify the solubility of the catalyst, facilitating partitioning of the catalyst into the precipitation solvent. Several types of molecules with varied functionality reduced the residual catalyst level to 30–120 ppm, depending on the loading. Hydrogenation of the polymer backbone followed by precipitation lowered the residual Ru content from 195 ppm to 10 ppm, suggesting that the difficulty of completely removing the catalyst could be a result of coordination of the metal species to the double bonds in the polymer backbone. Reducing the amount of trace catalyst significantly improved the oxidative stability of the polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Ring-opening polymerization of 2-azabicyclo-[2,2,1]-hept-5-en-3-one using metathesis catalysts

The ring-opening polymerization of an unsaturated bicyclic lactam, 2-azabicyclo-[2,2,1]-hept-5-en-3-one (ABHEO), was carried out using metathesis catalysts under various reaction conditions. It is observed that the best results (34% conversion and η_inh: 0.18 dL/g) were obtained when the mole ratios of ABHEO to WCl₆ as a catalyst and WCl₆ to AlEt₃ as a cocatalyst were 200 and 4, respectively. The infrared (IR) and nuclear magnetic resonance (¹H- and ¹³C-NMR) spectra of the polymer obtained indicated that the ABHEO was transformed to the ring-opened polymer, poly(2-pyrrolidone-3,5-diylvinylene) [poly(ABHEO)]. The resulting polymer was amorphous as determined by DSC analysis, which showed only secondary transition at 100°C.     

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.