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We report an examination of the ring-opening metathesis polymerization (ROMP) of endo-dicyclopentadiene (DCPD) by 10 well-defined molybdenum-based and 16 tungsten-based alkylidene initiators. Five tungsten-based MAP (monoaryloxide pyrrolide) initiators with the general formula W(X)(CHCMe2Ph)(Me2Pyr)(OAr) (X = arylimido, alkylimido, or oxo; Me2Pyr =2,5-dimethylpyrrolide; OAr = an aryloxide) were found to yield >98% cis, >98% syndiotactic poly(DCPD); they are W(N-t-Bu)(CHCMe3)(pyr)(OHMT) (2, OHMT = O-2,6-(2,4,6-Me3C6H2)2C6H3, pyr = pyrrolide), W(N-2,6-i-Pr2C6H3)(CHCMe2Ph)(pyr)(OHMT) (3), W(O)(CHCMe2Ph)(Me2Pyr)(OHMT)(PPh2Me) (7, Me2Pyr =2,5-dimethylpyrrolide), W(O)(CHCMe2Ph)(Me2Pyr)(ODFT)(PPh2Me) (9, ODFT = O-2,6-(C6F5)2C6H3), and W(O)(CHCMe2Ph)(Me2Pyr)(OTPP)(PMePh2) (10, OTPP = O-2,3,5,6-Ph4C6H). Two biphenolate alkylidene complexes, Mo(N-2,6-Me2C6H3)(CHCMe2Ph)(rac-biphen) (17) and W(N-2,6-Me2C6H3)(CHCMe2Ph)(rac-biphen) (22, biphen =3,3′-(t-Bu)2-5,5′-6,6′-(CH3)4-1,1′-biphenyl-2,2′-diolate), were found to yi...

We report the synthesis of >98% cis,isotactic and cis,syndiotactic polynorbornene (poly(NBE)) and poly(endo,anti-tetracyclododecene) (poly(TCD)). Cis,isotactic poly(NBE) and poly(TCD) were prepared employing Mo-based biphenolate imido alkylidene initiators, Mo(NR)(CHCMe2Ph)(Biphen) (Biphen = e.g., 3,3′-(t-Bu)2-5,5′-6,6′-(CH3)4-1,1′-biphenyl-2,2′-diolate), while cis,syndiotactic poly(NBE) and poly(TCD) were prepared employing W-based imido or oxo monoaryloxide pyrrolide (MAP) initiators, W(X)(CHR′)(Pyrrolide)(OTer) (X = NR or O; OTer = a 2,6-terphenoxide). Addition of 1-hexene or coordinating solvents such as THF do not decrease the stereospecificity of the polymerization. Cis,iso and cis,syndio dyads can be distinguished through examination of 1H and 13C NMR spectra of the two polymers in a mixture. The polymers were hydrogenated to give isotactic and syndiotactic H-poly(NBE) and H-poly(TCD).

Ring-opening metathesis polymerization (ROMP) of methyl-N-(1-phenylethyl)-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylate (PhEtNNBE; (S) and racemic) was investigated employing six molybdenum and tungsten imido alkylidene initiators and two tungsten oxo alkylidene initiators. Of the six initiators that we proposed should yield cis,syndiotactic-poly[(S)-PhEtNNBE], two molybdenum OHMT alkylidene initiators, Mo(NR)(CHMe2Ph)(pyr)(OHMT) (R = 1-adamantyl (Ad) or 2,6-Me2C6H3 (Ar′); OHMT = O-2,6-mesityl2C6H3; pyr = pyrrolide), and two tungsten oxo alkylidene initiators, W(O)(CHMe2Ph)(2,5-dimethylpyrrolide)(PMe2Ph)(OR) (OR = OHMT or (R)-OBr2Bitet where (R)-Br2BitetOH = (R)-3,3′-dibromo-2′-(tert-butyldimethylsilyloxy)-5,5′,6,6′,7,7′,8,8′-octahydro-1,1′-binaphthyl-2-ol), produced essentially pure cis,syndiotactic-poly[(S)-PhEtNNBE]. Essentially pure cis,isotactic-poly[(S)-PhEtNNBE] was formed when (S)-PhEtNNBE was polymerized by Mo(NAr′)(CHCMe2Ph)(OBiphenCF3)(thf) or W(NAr′)(CHCMe2Ph)((S)-OBiphenMe) (OBiphenCF3 = 3,3′-d...

Upon treatment with a molybdenum-carbene with bidentate substituted biaryl-o,o′-diphenoxide ligand 12, norbornene fused with N-aryl-endo-pyrrolidine 9a undergoes ROMP to give exclusively polynorbornene with cis, isotactic-selectivity. Bis(norbornenes) connected with ferrocene 18 or benzene 20 linkers yield the corresponding double-stranded ladderphanes 19 and 21, respectively with isotactic stereochemistry having all double bonds in Z-configuration. Like the corresponding ladderphanes with E-double bonds, ladderphane 19 also assembles on HOPG to give a highly ordered two-dimensional array as revealed by STM images.

We report the Z-selective and syndioselective polymerization of 2,3-bis(trifluoromethyl)bicyclo[2.2.1]hepta-2,5-diene (NBDF6) and 3-methyl-3-phenylcyclopropene (MPCP) by monoaryloxide monopyrrolide imido alkylidene (MAP) catalysts of Mo. The mechanism of polymerization with syn-Mo(NAd)(CHCMe(2)Ph)(Pyr)(OHIPT) (1; Ad = 1-adamantyl, OHIPT = O-2,6-(2,4,6-i-Pr(3)C(6)H(2))(2)C(6)H(3)) as the initiator is proposed to consist of addition of monomer to the syn initiator to yield a syn first insertion product and propagation via syn insertion products. In contrast, the mechanism of polymerization with syn-Mo(NAr)(CHCMe(2)Ph)(Pyr)(OTPP) (4; Ar = 2,6-i-Pr(2)C(6)H(3), OTPP = 2,3,5,6-Ph(4)C(6)H) as the initiator at -78 °C consists of addition of monomer to the syn initiator to yield an anti first insertion product and propagation via anti insertion products. Polymerizations of NBDF6 and MPCP at room temperature initiated by 4 led to polymers without a regular structure. We propose that the syndiotacticity of cis polymers is the consequence of the required inversion at the metal center with each insertion of monomer, i.e., stereogenic metal control of the polymer structure. We also propose that the two mechanisms for forming cis,syndiotactic polymers arise as a consequence of the relative steric bulk of the imido and phenoxide ligands.

A series of monomers with side chain liquid crystals (SCLCs) were synthesized for ring opening metathesis polymerization (ROMP). The liquid crystals (LCs) used were 4-hydroxybenzoic acid 4-methoxyphenyl ester (MPOB-H), which is known to exhibit a nematic liquid crystalline phase, and biphenyl-4-carboxylic acid 4-(1-butoxycarbonylethoxy)phenyl ester (BPP4-H), which is known to exhibit a smectic phase. The side chains differed in spacer length, spacer type, and the nature of the LC. Monomers were polymerized using a bimetallic ROMP initiator [Mo(NAr)(OCMe3)2CH]2C6H4 (where Ar = 2,6-diisopropyl phenyl); both homopolymers and ABA type triblock copolymers, where the B block is the LC functional monomer, and A is methyltetracyclodocene (MTD) were prepared. The polymers gave unimodal peak distributions with polydispersities

A series of monomers suitable for ring-opening metathesis polymerization (ROMP) containing a side chain liquid crystal mesogen have been synthesized, where the mesogen is biphenyl-4-carboxylic acid 4-(1-butoxycarbonyl-ethoxy)phenyl ester (abbreviated as BPP4). Two of the monomers have BPP4 attached to norbornene with a 6- or 10-carbon spacer ((R)-4‘-(5-bicyclo[2.2.1]hept-5-en-2-yl-pentyloxy)-BPP4, NB6wBPP4, and (R)-4‘-(10-bicyclo[2.2.1]hept-5-en-2-yl-decyloxy)-BPP4, NB10wBPP4, respectively), and the third monomer has BPP4 attached to norbornadiene via a 10-carbon spacer ((R)-4‘-(10-bicyclo[2.2.1]hepta-2,5-dien-2-yl-decyloxy)-BPP4, NBD10wBPP4). The monomers were polymerized by ROMP using the bimetallic initiator, {Mo(NAr)(ORF6)2[=CHC5H4]}2Fe (Ar = 2,6-diisopropylphenyl, ORF6 = OCMe(CF3)2). ABA triblock copolymers were also synthesized where the B = NBD10wBPP4 or NBnwBPP4 (n = 6, 10) and A = methyltetracyclododecene (MTD). All polymerizations are living with isolated yields greater than 90% and polydispersi...

Efficient routes to sulfonation and epoxidation of the double bonds in a polynorbornene backbone have been found that do not interfere with side chain functional groups of interest for making light-emitting devices. Substituted norbornene monomers were prepared with ether or thioether linkages, which were stable to sulfonation. Oligomers (25mers or 50mers) of homo- and copolymers containing diphenylanthracene (for blue-light emission), oxadiazole (for electron transport), and p-triphenylene (for hole transport) side chains were prepared via ring-opening metathesis polymerization (ROMP) of the corresponding norbornene monomers. Sulfonation of the polynorbornene backbone yielded a polyanionic material that was suitable for creating films via sequential adsorption with the polycation, poly(allylamine HCl) (PAH). Devices with an indium tin oxide (ITO) anode and an aluminum cathode were constructed. A two-layer device comprised of a layer of diphenylanthracene/oxadiazole copolymer and a layer of p-triphenylene...

A blue-light-emitting electroluminescent polymer was prepared by ring-opening metathesis polymerization (ROMP) of norbornene monomer that contains a diphenylanthracene chromophore as a side chain (λ max.em = 450 nm). Norbornene monomers also were synthesized that contain an oxadiazole (for electron transport) or a tertiary arylamine (for hole transport). Oligomers (25mers or 50mers) of homo- and copolymers (M w /M n = 1.02-1.08) were prepared in toluene in 95-98% yield, employing Mo(N-2,6-C 6 H 3 -i-Pr 2 )(CHMe 2 Ph)(O-t-Bu) 2 as the initiator. Electroluminescent devices made with a single layer of substituted polynorbornene, an ITO anode, and an Al cathode were prepared first. Two-layer devices were then constructed in which the substituted polynorbornene was spin cast onto a 25-bilayer poly(phenylenevinylene)(PPV) heterostructure. The two-layer device performed best in terms of efficiency, light output, and threshold voltage.

Nearly monodisperse CdSe nanoclusters, surface-passivated with a layer of trioctylphosphine and trioctylphosphine oxide, have been sequestered within phosphine-containing domains in a diblock copolymer. A convergent approach to fabrication of these composites was adopted via independent synthesis of nanoclusters and polymer. Diblock copolymers of phosphine- or phosphine oxide-functionalized monomers and methyltetracyclododecene (MTD) were prepared by ring opening metathesis polymerization using Mo alkylidene initiators. Nanoclusters were prepared by pyrolysis of CdMe2 and SeP(octyl)3 in the presence of P(octyl)3 and OP(octyl)3. An immediate and sustained increase in electronic passivation is found for nanoclusters incorporated into octylphosphine-containing polymers. In contrast, nanoclusters in pure hydrocarbon or phosphine oxide-containing polymers rapidly lose passivation. Films of nanoclusters in a phosphine-containing polymer matrix were static cast from dilute solution. Under suitable conditions, th...

Ring-opened homopolymers of 5-norbornene-2-carboxylates or 5-norbornene-2,3-dicarboxylates that contain acetal-protected sugars (1: 1,2:3,4-di-O-isopropylidene-α-d-galactopyranos-6-O-yl 5-norbornene-2-carboxylate; 2: bis(1,2:3,4-di-O-isopropylidene-α-d-galactopyranos-6-O-yl) 5-norbornene-trans-2,3-dicarboxylate; 3: 5-norbornene-2-carboxylic acid ester containing 2,3-O-isopropylidene-d-ribonic γ-lactone; 4: 3,4:5,6-di-O-isopropylidene-α-d-mannofuranos-1-O-yl 5-norbornene-2-carboxylate) were prepared in toluene using Mo(CHCMe2Ph)(N-2,6-i-Pr2C6H3)(O-t-Bu)2 as the initiator. These homopolymers showed narrow molecular weight distributions (PDI = 1.02−1.25) and a molecular weight dependent on the number of monomers added. Di-, tri-, and tetrablock copolymers containing 1−4, methyltetracyclododecene (MTD, 5), or trans-2,3-bis(((trimethylsilyl)oxy)methyl)-norborn-5-ene (6) were also prepared and found to have low polydispersities (Mw/Mn = 1.03−1.25). The cyclic acetal in polymers containing 1 or 2 could be re...

Several racemic or enantiomerically pure complexes of the general type Mo(CHR)(NR‘)(O2R‘‘) that contain binaphtholate or biphenolate (O2R‘‘) ligands have been prepared and employed to ring open several achiral, racemic, or enantiomerically pure norbornenes and norbornadienes. A bimodal molecular weight distribution sometimes results from polymerization of an enantiomerically pure monomer with a racemic initiator as a consequence of a different rate of chain growth from enantiomeric metal centers. The analogous polymerization of an enantiomerically pure monomer with an enantiomerically pure initiator yields only a single polymer chain, as expected. Evaluation of the cis content of the resulting polymers suggests that cis polymer results from polymerization via syn alkylidene propagating species and that accessibility of the anti rotamer on the polymerization time scale is determined by a subtle combination of steric bulk in the biphenoxide and imido ligands. All cis polymers were found to be highly isotact...

We describe the living polymerization of ethynylferrocene and ethynylruthenocene and the copolymerization of ethynylferrocene and TCDTF6 (TCDTF6 = 7,8-bis(trifluoromethyl)tricyclo[4.2.2.0 2,5 ]-deca-3,7,9-triene). In all cases Mo(N-2,6-Me 2 C 6 H 3 )(CHCMe 2 Ph)[OCMe(CF 3 ) 2 ] 2 was the initiator that was employed. Charged systems were generated by terminating the living polymer with pyridinecarboxaldehyde followed by quaternizing the tertiary nitrogen with methyl iodide. Polyenes and copolyenes that contain up to ∼50 double bonds are soluble. Charged polymers exhibit a more intense and red-shifted absorption. NMR studies suggest that ethynylferrocene adds to the initiator to give an unobservable intermediate α-substituted metallacyclobutene that opens to give the disubstituted (ferrocenyl/vinyl) propagating alkylidene. The structures of the first and second insertion products obtained by capping the chain with ferrocenecarboxaldehyde or pyridinecarboxaldehyde confirm that α addition takes place, a trans double bond is formed, and polymerization is virtually exclusively head-to-tail. Ethynylferrocene reacts extremely slowly with Mo(N-2,6-Me 2 C 6 H 3 )(CHCMe 2 Ph)(O-t-Bu) 2 via α addition and with Mo(NAr)-(CHCMe 2 Ph)(OC 6 F 5 ) 2 (quinuclidine) and Mo(NAd)(CHCMe 2 Ph)[OCH(CF 3 ) 2 ] 2 (2,4-lutidine) via β-addition.

The factors that determine the structure (cis/trans and tacticity) of polymers prepared by ring-opening metathesis polymerization (ROMP) from 2,3-bis(trifluoromethyl)norbornadiene (NBDF6) and several bis(carboalkoxy)norbornadienes using well-defined initiators of the type Mo(NAryl)(CHCMe 2 -Ph)(OR) 2 (Aryl = a substituted aryl group and OR = a variety of alkoxides) have been explored. The main finding is a dependence of cis/trans structure on temperature ; at low temperatures (-35 °C) all-cis polymer is formed and at high temperatures (65 °C) up to 90% trans polymers are formed. These results are consistent with formation of cis polymer from syn alkylidene rotamers and trans polymer from anti alkylidene rotamers in circumstances where syn and anti rotamers can interconvert. Several all-cis polymers prepared from achiral initiators that contain various fluorinated alkoxides were found to be biased toward isotacticity. In one case, however, the polymer was biased toward syndiotacticity.

A blue-light-emitting electroluminescent polymer was prepared by the ring-opening metathesis polymerization (ROMP) method from a norbornene monomer (NBTPV-C5) that contains a phenylenevinylene oligomer unit as a side chain. A 50mer of NBTPV-C5 (M w /M n =1.10) was prepared in THF in 95% yield by employing Mo(NAr)(CHCMe 3 Ph)(O-t-Bu) 2 as the initiator. Electroluminescent devices were made with single layers of polyNBTPV-C5 with ITO as the anode and Ca as the cathode, both by itself and in blends containing the electron transport material, biphenyl-tert-butylphenyloxadiazole. Two layer devices using PPV as a hole transport layer also were prepared. Electroluminescent quantum yields of up to 0.55% have been obtained

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.

Ring-opened polymers of (+)- and (-)-endo,exo-5,6-dimethylbicyclo2.2. 1hept-2-ene (1) having cis double bond contents between 5 and 85% were prepared using Mo(CH-t-Bu)(NAr)(OR)2 (Ar = 2,6-C6H3-i-Pr2; OR = OCMe3, OCMe2(CF3), OCMe(CF3)2) complexes as initiators. The cis content of the polymers increased in proportion to the electron-withdrawing power of the alkoxide ligands. 13C NMR spectra (125 MHz) of these polymers were interpreted in terms of the various possible types of dyad structure: XX, XN (NX), NN, where X and N refer to substituents derived from exo and endo methyl groups, m and r refer to the meso (isotactic) or racemic (syndiotactic) configuration of adjacent cyclopentane rings in the chain, and tt, tc, (ct), and cc refer to the cis/trans double bond sequences. High cis polymer made from 98% (+)-l contained 78% m dyads and had more than twice the optical rotatory power and a higher Tg (85 deg C) compared to a high trans polymer (48% m dyads; Tg = 55 deg C).

Polymers were prepared by living ring-opening metathesis polymerization employing Mo(CH-t-Bu)(NAr)(O-t-Bu) 2 (Ar=2,6-C 6 H 3 -i-Pr 2 ) as the initiator. Norbornene, 5-cyano-2-norbornene, and methyltetracyclododecene were used for the amorphous polymer block and n-[((4'-methoxy-4-biphenyl)yl)oxy]alkyl bicyclo[2.2.1]hept-2-ene-5-carborylates (1-n, n=3, 6) were used for the side-chain liquid crystal (SCLC) block. Block copolymers with monomer ratios from 75/25 to 20/80 (amorphous/SCLCP) and narrow molecular weight distributions were obtained in high yield.

Norbornene derivatives containing 4'-cyano-4-biphenyloxy mesogens linked to the norbornene through methylene groups (n = 3-7, 9-12) and an ester were polymerized by Mo(CHR)(NAr)(O-t-Bu)2 (Ar = 2,6-C6H3-i-Pr2, R = t-Bu) in a living manner. Polymers in which n = 3 were amorphous, whereas all other polymers (n = 4-7, 9-12) displayed enantiotropic nematic mesophases that were independent of the molecular weight. Polymers having 9-12 methylene spacers did not undergo side chain crystallization and did not show an odd-even effect, in contrast to analogous polymers containing 4'-methoxy-4-biphenyloxy mesogens, which exhibited side chain crystallization when n > 8 and an odd-even effect when n < 7. The lower tendency to form a more ordered phase and the absence of an odd-even effect are attributed to dipole-dipole repulsions between 4'-cyano- 4-biphenyloxy mesogens. Polymers containing 4'methoxy-4-biphenyloxy mesogens attached through ether linkages gave highly crystalline SCLPCs, even with relatively few spacers (n = 4-6 ). polymers, SCLPCs (side chain liquid crystalline polymers), block copolymers, mesogens.

The living ring opening metathesis polymerization of 5-carbo(n-(4'- methoxy-4-biphenylyl)oxy)alkyl)bicyclo(2.2.1)hept-2-ene (1-n, n=2-8) by Mo(CH-t- Bu)(NAr) (0-t-Bu)2(Ar=2,6-C6H3-t-Pr2) is described. Polymers with degrees of polymerization from 5 to 100 and narrow molecular weight distributions (Mw/Mn=1. 05-1.24) were obtained in high yield. All polymers exhibit an enantiomorphic nematic mesophase. Glass transition and isotropization temperatures increase with increasing molecular weight and become independent at approximately 30-50 repeat units. The change in enthalpy of isotropization is relatively independent of molecular weight. Using polymer blends, it was shown that polydispersity has no effect on either the transition temperatures or the temperature range of isotropization. Isotropization alternates in an odd-even manner up to spacer lengths of n=6, and then levels off. Living ring opening metathesis polymerization, Side chain liquid crystalline polymers (SCLCPs).

Norbornene derivatives containing laterally attached 2,5-bis(4'-n- alkoxybenzoyl OXY) mesogens were polymerized by controlled ring opening metathesis polymerization to provide polymers in high yield with 5-100 repeat units and narrow molecular weight distributions. Monomers with n>l displayed monotropic or enantiotropic nematic mesophases. All polymers displayed enantiotropic nematic mesophases regardless of the spacer, molecular weight or length or the n-alkoxy substituent. Constitutional isomers of poly(5-carbo(2', 5'-bis-4( methoxybenzoyloxy)benzyloxy)bicyclo(2.2.1)hep t-2-ene)s containing laterally attached mixed phenylester/benzylester units are amorphous. Side chain liquid crystal polymers (SCLCPs), living ring opening metathesis polymerization.

Diblock copolymers of norbornene and Sn[2,3-trans-bis-([tert-butylamido]methyl)norborn-5-ene]Cl 2 were prepared by ring opening metathesis polymerization using a tungstene alkylidene catalyst. TEM and SAXS data showed that these copolymers exhibited spherical, cylindrical or lamellar morphology depending on their composition and molecular weight. The phase diagram compared well with the predictions of the Helfand and Wasserman theory.

Norbornenes containing esters, cyano, acetate, and related functionalities can be polymerized in a living manner employing Mo(CH-t-Bu)(NAr) (O-t-Bu)2 as the initiator, especially in THF, to give polymers with polydispersities as low as 1.04. Living polymers containing Mo-alkylidene end groups have been characterized by proton NMR methods.

L'addition du dimere du norbornadiene ou polynorbornene obtenu par polymerisation par metathese amorcee par (CHR) (NR) (O-t-Bu) 2 (M=Mo, W) donne des polymeres en etoile. Des copolymeres en etoile sont prepares par reaction du 2,3-bis (trifluoromethyl)- ou du 2,3-bis(methoxycarbonyl)-norbornadiene avec le poly(5-cyanonorbornene) vivant en etoile obtenu par cette methode

The synthesis of amphiphilic star block copolymers by ring opening metathesis polymerization using a new cross-linking agent and appropriately functionalized norbornene-type monomers is reported

Preparation des polymeres tBu-CH(=CH-(C 5 H 8 )-CH) n =CH-PhX (X=OMe, NMe 2 , CN, NO 2 , CHO, CO 2 MC, NH 2 , CF 3 -Cl) par reaction du polymere vivant avec le benzaldehyde substitue correspondant

Addition de cyclooctyne a W 2 (O-t-Bu) 6 dans le toluene ou le dichloromethane. Temperatures de fusion (62±4 o C), de transition vitreuse (65 o C) et de degradation thermique (390 o C)

Polymerisation avec le systeme W(CH t Bu)(N Ar) [OCMe(CF 3 ) 2 ] 2 , dans le toluene entre −40 et −20 o C

Utilisation d'alkenyl-3 cyclopentenes comme agents de transfert de chaines pour separer le polymere en formation de l'amorceur de polymerisation vivante ROMP du type M(CH-P)(NAr)(O-t-Bu) 2 (M=Mo ou W, P=polymere, Ar=diisopropyl-2,6 phenyl) et regenerer le complexe alkylidene amorceur, en se basant sur le principe qu'un cyclopentene s'ouvrira par reaction avec la double liaison du complexe W=CHP et qu'un cyclohexene sera reforme par reaction avec la double liaison de la chaine alkenyl

Polymerisation en presence des complexes Ta(CHt-Bu)(OR) 3 (THF) avec OR=diisopropyl-2,6 phenylate ou dimethyl-2,6 phenylate

Addition of 50-200 eq of norbornene to Mo(CH Superscript t Bu) (NAr) (O Superscript t Bu)2 yields living polymers, Mo?CH(C5H8)CHxCH Superscript t Bu (NAr)(O Superscript t Bu)2 (55% trans), that are stable for days in the absence of water and oxygen with essentially no isomerization of the double bonds in the chain. Addition of benzaldehyde cleaves off the polymer in a Wittig-like reaction to yield polynorbornenens with polydispersities in the range 1.04-1.11. Analogous reactions involving 50-200 eq of endo, endo-5,6-dicarbomethoxynorbornene yields homopolymers with polydispersities in the range 1.11-1.22. Block copolymers containing 50 eq of endo,endo-5,6-dicarbomethoxynorbornene and 200 eq of norbornene prepared by adding one or the other monomer first are virtually identical (polydispersities 1.06 and 1.09 with M sub n 57200 and 59900, respectively). These results suggest that the molybdenum catalyst will not react significantly with up to 100 eq of ester functionality during the time of a typical polymerization reaction (approx. 15 m at 25 degs.).