Showing papers on "Norbornene published in 1995"

Ruthenium-based catalysts for the ring opening metathesis polymerisation of low-strain cyclic olefins and of functionalised derivatives of norbornene and cyclooctene

Abstract: New, readily available catalyst systems based on [(arene)RuCl2phosphine] complexes activated by addition of trimethylsilyldiazomethane are very active for promoting the ring opening metathesis polymerisation (ROMP) of functionalised norbornenes and cyclooctenes.

Synthesis of block copolymers of silicon-containing norbornene derivatives via living ring-opening metathesis polymerization catalyzed by a ruthenium carbene complex

Abstract: Block copolymers (5) of silicon-containing norbornene derivatives were prepared using living ring-opening metathesis polymerization (ROMP) with a well-defined ruthenium carbene complex [1, (R 3 P) 2 Cl 2 Ru=CHCH=CPh 2 ; 1a, R = phenyl ; 1b, R = cyclohexyl]. For example, the living polymerization of norbornene 2a (NBE) by 1a was carried out at room temperature in a mixture of methylene chloride and 1,2-dichloroethane. After 3 h, the polymer isolated had a narrow molecular weight distribution (MWD) (M n = 58 000, M w /M n = 1.20). On addition of a silicon-containing norbornene derivative (4), polymerization immediately ensued at 50 °C from the living ends of 3 and afforded a block copolymer 5a. The MWD curve of the resulting block polymer 5a shifted toward the higher molecular weight region, and the polydispersity remained narrow (M n = 129 000, M w /M n = 1.25). The segment ratio (m :n = 1.86) of 5a determined by 1 H NMR was in good agreement with the calculated value (m :n = 1.78). Silicon-containing block copolymers with polar functional groups were also synthesized by ROMP with 1b.

Hydrooligomerization of cycloolefins -a view of the microstructure of polynorbornene

Abstract: Hydrooligomerizations of norbornene were carried out using C 2 , C s and C 2 v symmetric zirconocenes with methylaluminoxane as catalysts. The structures of the hydrodimers and -trimers were investigated and correlated to the symmetry of the metallocene. The polymerization of norbornene is shown to proceed by cis-exo insertion. The mechanisms of polymerization and stereocontrol are closely related to the ones observed in the polymerization of α-olefins. Thus the C 2 symmetric metallocene features erythrodiisotactic structures, while erythrodisyndiotactic products are observed in case of the C s symmetric one. This is caused by enantiomorphic site control, while stereospecificity in the hydrooligomerization using Cp 2 ZrCl 2 MAO is determined by chain end control mechanism.

The Chemistry of Phenol-Formaldehyde Resin Vulcanization of EPDM: Part I. Evidence for Methylene Crosslinks

Abstract: The application of phenol-formaldehyde resins as crosslinking agents is increasing in importance due to the good high temperature properties of the corresponding vulcanizate and the use in thermoplastic vulcanizates. With respect to the chemistry of phenol-formaldehyde cure (reaction mechanism and structure of crosslink) there are still problems that have to be resolved. The reaction products of the phenol-formaldehyde resin curing of EPDM, contain 2-ethylidene norbornene (ENB) as the third monomer, have been studied. Since such an investigation is rather difficult to perform for the polymer system, a low molecular weight model for EPDM was used: 2-ethylidene norbornane (ENBH). Reaction of ENBH and a resole results in scission of the dimethylene ether bridges, i.e. in degradation of the resole into mono-, bis- and terisooctylphenol units. These are consequently converted into products, consisting of two ENBH molecules linked by mono-, bis- and terisooctylphenol units. The solid resole seems to be...

Pd(II) -catalyzed addition polymerizations of strained polycyclic olefins

Abstract: Cationic Pd(II) -complexes with weakly coordinating ligands were used for the olefin addition polymerization of strained polycyclic olefins. The cyclic structure of the monomers remained intact during the reaction which contrasts with products obtained from the olefin metathesis polymerization. The Pd(II) -catalyzed polymerizations showed the features of a “living” polymerization, when norbornene and selected exo-substituted norbornene derivatives were used as the monomers. Endo- and exo-dicyclopentadiene, exo-1,2-dihydrodicyclopentadiene, endo, exo-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene and endo, exo-1,4,5,8-dimethano-1,4,4,a,5,8,8a-hexahydronaphthalene were converted into the corresponding rigid polymers. The exo-substituted monomers were found to polymerize at a higher rate than the corresponding or similar endo-substituted monomers. The polymerization of norbornadiene and the subsequent thermal elimination of cyclopentadiene resulted in the formation of polyacetylene.

Olefin terpolymerizations. III. Symmetry, sterics, and monomer structure in ansa‐zirconocenium catalysis of EPDM synthesis

Abstract: Ethylenebis (η5-fluorenyl) zirconium dichloride (1) and rac-dimethylsilylene bis (1-η5-in-denyl) zirconium dichloride (2) were activated with methylaluminoxane (MAO) to catalyze ethylene (E) propylene (P) copolymerizations. The former produces high MW copolymer at 20°C rich in ethylene with reactivity ratio values of rE = 1.7 and rP <0.01, whereas the latter produces lower MW random copolymers with rE = 1.32 and rp = 0.36. Ethylidene norbornene (ENB) complexes with 1/MAO but does not undergo insertion in the presence of E and P. In contrast, 2/MAO catalyzes terpolymerization incorporating 9-15 mol % of ENB with slightly lower MW and activity than the corresponding copolymerizations. In comparison, 1,4–hexadiene was incorporated by 2/MAO with much lower A and MW. Terpolymerizations were also conducted with vinylcyclohexene using both catalyst systems. The steric and electronic effects in these processes were discussed. © 1995 John Wiley & Sons, Inc.

Metal catalyzed polycondensation reactions

Abstract: Metal catalyzed polymerizations are chain reactions necessitating a constant valence of the metal. In contrast to that metal catalyzed polycondensations are step growth reactions involving a change of the valence of the metal. Tuning of the reaction by structural variations of the metal catalyst are demonstrated with the Pd-catalyzed vinyl polymerization of norbornene, the alternating copolymerization of ethylene with carbon monoxide and the Heck reaction as examples. One and two electron processes can be involved in metal catalyzed polycondensations. The oxidative polymerization of 2,6-dimethylphenol, the Heck reactions as well the Ni-catalyzed synthesis of polyphenylenes are discussed.

Hydrogenated ring-opening polymer

Abstract: A thermoplastic norbornene resin having the number-average molecular weight (Mn) of at least 12,000 (in terms of polyisoprene) as measured by gel permeation chromatography and being lowly birefrigent and excellent in the resistance to oils and greases is obtained by subjecting polycyclic norbornene monomers containing at least 70 % by weight of a norbornene monomer represented by general formula (I) (for example, 1,4-methano-1,4,4a, 9a-tetrahydrofluorene) to ring-opening polymerization and then hydrogenating the obtained polymer in such a manner as to give the hydrogenation ratio of the double bond in the main chain of at least 98 % and the hydrogenation ratio of the six-membered ring structure of at least 90 %, wherein the lowermost 6-membered ring may have a double bond.

Preparation of 1-Propenyl Ether Functional Siloxanes by Chemoselective Hydrosilation and Their Cationic Photopolymerization

Abstract: Using model compounds, it was shown that the hydrosilation of (1-propenoxy)norborn-5-enes takes place chemoselectively only at the norbornene double bond. Accordingly, a variety of mono-, di-, and multifunctional 1-propenyl ether substituted siloxanes were readily prepared in high yields by the hydrosilation of (1-propenoxy)norborn-5-enes with various linear and cyclic hydrogen functional siloxanes. These new monomers and oligomers undergo rapid photoinduced cationic polymerization in the presence of onium salt photoinitiators. To study these very fast photopolymerizations, extensive use of Fourier transform real-time infrared spectroscopy was made. Employing this technique, the effects of monomer and photoinitiator structure on the rates of polymerization were studied.

Monomers and composition which can be crosslinked and crosslinked polymers

Abstract: The invention concerns compounds of formula (I) (A)n-B in which A is an extended cycloolefin group, B stands for a direct bond or an n-valent bridging group, and n is an integer from 2 to 8, with the exception of 1,2-bisnorbornenyl ethane and norbornene carboxylic acid norbornene methylester. The compounds of formula (I) can be polymerized with single-component catalysts (ring-opening metathesis polymerization).

Synthesis of Polynorbornene Containing Fluorescein Moiety

Abstract: A novel fluorescein-containing norbornene monomer was synthesized. This monomer copolymerized with norbornene via ring opening to give high molecular weight polymers. It gave a homopolymer with a Pd-containing catalyst opening of its double bond. All polymers exhibited absorption and emission spectra similar to those of fluorescein.

Structure-reactivity correlations in the reactions of hydrocarbons on transition metal surfaces. 2. Hydrogenation of norbornene and bicyclo[2.2.2]octene on platinum(111)

Abstract: The reactivity of two bicyclic alkenes, bicyclo(2.2.2)octene (BOE) and norbomene (NBE), has been studied on Pt(ll1) in both the absence and the presence of co-adsorbed hydrogen. The inability of these alkenes to rearrange to alkylidyne species on the surface considerably alters their reaction chemistry. At 130 K, the alkenes are bound molecularly to the surface via two interactions: (1) a z or di-a interaction with a C=C double bond, and (2) an apparent agostic interaction with a C-H bond. The geometries of these bicyclic alkenes strongly suggest that they are interacting with three mutually-adjacent surface Pt atoms, but it is not clear from the data whether the alkene group bridges between two Pt atoms and the agostic interaction involves one Pt atom or vice versa. Several reactions ensue upon thermolysis. At -250 K, the agostic C-H bond is cleaved and a surface-bound alkyl intermediate is formed. The resulting surface-bound hydrogen atoms do not immediately desorb, but some of them transfer to unreacted BOE and NBE molecules to form the alkanes bicyclo(2.2.2)octane (BOA) and norbomane (NBA), respectively. The rate-detennining step for this self-hydrogenation reaction is the dehydrogenation of BOE or NBE; these processes appear to follow first-order rate laws with activation energies of -16 kcdmol. If the FT( 11 1) surface is first treated with hydrogen and then dosed with the bicyclic alkene, alkane is formed at lower temperatures (as low as 190 K) and in significantly greater amounts. In the presence of co-adsorbed Dz, BOE and NBE are hydrogenated to a distribution of alkane isotopomers with up to four deuterium atoms per molecule; these observations suggest that the surface-bound alkyl intermediates can a-eliminate and reversibly form alkylidenes. Surface carbon atoms, when present at sufficiently high coverages, inhibit the hydrogenation and self-hydrogenation of these bicyclic alkenes due to the reduced ability of the carbonaceous Pt( 11 1) surface to activate H-H or C-H bonds. At higher temperatures (470-520 K), both BOE and NBE eventually decompose to give benzene (part of which desorbs) and surface C,H, fragments. The latter decompose by -620 K to give a partial carbonaceous overlayer and HZ gas.

Synthesis and Nonlinear Optical Characterization of Spin-Coated Films of Triblock Copolymers Containing Durham Polyacetylene

Abstract: Sequential ring-opening metathesis polymerization of either norbornene or 9-methyltetracyclo-[6.2.1,1 3.6 .0 2,7 ]dodec-4-ene (MTD) and 7,8-bis(trifluoromethyl)tricyclo[4.2.2.0 2,5 ]deca-3,7,9-triene (TCDT) with Mo(CHCMe 3 )(NAr)(OCMe 3 ) 2 (Ar = 2,6-diisopropylphenyl) followed by linking termination with a conjugated dialdehyde results in highly soluble A-B-A triblock copolymers containing a precursor to Durham polyacetylene as the central block. A series of copolymers that contained from 10 to 200 equiv of TCDT was synthesized. The precursor copolymers were spin coated to give submicron thin films. In the case of the copolymers made with norbornene, higher spin speeds resulted in a red shift of the UV/vis spectra of the final polyacetylene-containing copolymer, indicative of longer average conjugation lengths within the film. A red shift was also observed in the UV/vis spectra of copolymers made with more equivalents of TCDT. The nonlinear optical susceptibility (X (3) ) of the copolymers was probed with third harmonic generation and degenerate four-wave mixing. X (3) increased with increasing equivalents ofTCDT. In all cases, the copolymers made with norbornene had larger X (3) values than the copolymers made with MTD.

Azo bridges from azines, XIV. Rigid polycycles with NN and CC functionalities

Abstract: Bifunctional 9, 3, 17, and trifunctional 20 dienophiles have been subjected to Diels-Alder reactions with 4H-pyrazoles 8 or 14 with inverse electron demand to form monoadducts 13, 15, 18, and 21 and bisadducts 16, 19, and 26. Acid-catalyzed reactions at 20°C occur according to 14 + 3 15 + 16 and 14 + 17 18 + 19. By contrast, the solution of barrelene (20) and 8 has to be subjected to 10 kbar and 130°C to give monoadduct 21 and bisadduct 26, In daylight 21 undergoes [2 + 2] cycloaddition to 27. The norbornene derivative 10 reacts with cyclopentadiene to form 13 which is obtained in higher yield by reaction of 10 with hexachlorocyclopenta-diene and subsequent reductive dehalogenation of adduct 12. X-ray analyses of 11 and 13 reveal only small differences in the structural parameters.

Chain polyene group-containing norbornene compound and unsaturated ethylene copolymer using the same

Abstract: The chain polyene-group containing norbornene compound of the invention is represented by the formula [I]: ... [I]wherein n is an integer of 1 to 5, R1 is an alkyl group of 1 to 5 carbon atoms, and R2 and R3 are each independently a hydrogen atom or an alkyl group of 1 to 5 carbon atoms. The unsaturated ethylene copolymer of the invention is a random copolymer of 30 to 92 % by mol of (i) ethylene units, 6 to 70 % by mol of (ii) specific .alpha.-olefin units and 0.1 to 30 % by mol of (iii) units derived from the norbornene compound [I], where the molar ratio of (i)/(ii) is in the range of 40/60 to 92/8 and the unit (iii) is represented by the specific formula, and has an intrinsic viscosity [.pi.] of 0.05 to 10 dl/g. The novel unsaturated ethylene copolymer is excellent in weathering resistance, heat resistance and ozone resistance and has a high vulcanizing rate.

Copolymerization process for the preparation of crystalline copolymers of olefins and cyclic olefins

Abstract: A copolymerization process suitable for the preparation of high crystalline melting point cyclic olefin copolymers comprising contacting ethylene, and at least one cyclic olefin with an active polymerization catalyst comprising a Group 4 transition metal compound containing an asymmetrically substituted monocyclopentadienyl ancillary ligand, a bulky substituent-containing heteroatom ligand, the monocyclopentadienyl and heteroatom ligands being covalently bridged is disclosed. Ethylene/norbornene copolymers prepared in accordance with the invention exhibited crystalline melting points of about 250° C., and were prepared at high catalyst activity levels with feed ratios less than 6:1 of norbornene to ethylene.

Vehicle parts comprising ethylene/2-olefin/vinylnorbornene elastomeric polymers

Abstract: Motor vehicle brake parts based on an ethylene, alpha-olefin, vinyl norbornene elastomeric polymer are manufactured with more efficiency due to brake part compounds having lower viscosity, faster and fuller cures than ethylene, alpha-olefins, diene monomer compounds, where the diene monomer is other than vinyl norbornene Additionally, the brake parts based on the ethylene, alpha-olefin, vinyl norbornene elastomeric polymer have improved resistance to elevated temperature properties, and good heat aging characteristics, compared to for instance ethylene, alpha-olefin, non-conjugated diene elastomers (where the diene is other than vinyl norbornene) or styrene butadiene rubbers

Selective hydrogenations of dienes and oiefins by [W2(OCH2But)6(py)2]

Abstract: Hydrocarbon solutions of [W2(OCH2But)6(py)2] in the presence of H2(3 atm, 23 °C) hydrogenate linear 1,3-dienes to 3-enes, 1,3- and 1,5-cyclooctadiene to cyclooctene, 1,3-cyclohexadiene to cyclohexene, cyclopentene to cyclopentane, and norbornene to norbornane, but do not hydrogenate α- and internal olefins to alkanes, or internal conjugated or unconjugated dienes.