Polymer-supported heterogeneous titanium-based Ziegler-Natta catalyst for ethylene polymerization

Reported here in, is the synthesis of polystyrene (PS)-supported Ziegler–Natta catalyst (PS-TiCl₄) by the reaction of PS and titanium tetrachloride (TiCl₄). PS was synthesized by emulsion polymerization using super critical CO₂ (sc-CO₂) as a medium. Three catalysts were synthesized by varying the TiCl₄/PS weight ratio in hexane medium. The resulting catalysts were characterized by Fourier transformed-infrared spectroscopy, UV–visible spectroscopy, scanning electron microscope and energy dispersive X-ray detector, X-ray diffraction analysis. The acidity of the catalysts in an acetone/water solution was measured by pH meter. The thermogravimetric analysis reveals that catalysts are stable upto 150–180°C. Due to their higher degree of thermal stability these catalysts may potentially be used as a support in conventional Ziegler–Natta catalyst for ethylene polymerization. These catalysts also showed good storability and its overall catalytic productivity are found to be 3720 g PE/g Ti. The productivity of the catalysts also depended on the titanium concentration in the polymer matrix. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ethylene polymerization on polymer supported Ziegler-Natta catalyst

Poly(styrene-co-methyl methacrylate) has been used as a support for titanium based Ziegler?CNatta catalyst. We have prepared three polymer supported catalysts by varying the weight ratio of TiCl₄ and polymer to perform the ethylene polymerization. Triethylaluminium (TEA) is used as cocatalyst. Catalysts have been characterized by XPS, FT-IR, UV-visible spectroscopy, XRD, pH meter, TGA and SEM-EDX. The catalysts are found to be stable upto 100?°C. Density functional theory (DFT) has been used to elucidate the structure of TiCl₄ and the polymer supported complex. All these spectroscopic analysis and density functional study confirm the incorporation of titanium into the polymer matrix. The catalytic activity is found to be in the range of 0.6?C1.01?kg of polyethylene (PE)/g Ti/h and the catalytic activity depends on the optimum level of Ti content. The molecular weight ( $ \overline {{M_w}} $ ) of PE is in the range of 237,300?C275,600?g/mol. Present study also reports the stability and storability of the catalysts.

Immobilization of Titanium Tetrachloride on Mixed Support of MgCl2 · xEB/Poly(methyl acrylate-co-1-octene): Catalyst for Synthesis of Broad MWD Polyethylene

TiCl₄ immobilization on different compositions of mixed support of MgCl₂ · xEB and poly(methyl acrylate-co-1-octene) (PMO; synthesized through ARGET ATRP) resulted in the formation of solid catalysts having variation in incorporation of titanium. The effect of mixed support composition onto the titanium immobilization, catalyst morphology and performance for ethylene polymerizations has been evaluated. The polyethylenes synthesized showed broad to bimodal MWD in GPC and DSC where the broadness was found to be dependent upon the ratio of mixed support MgCl₂ · xEB/PMO. The morphological features of PE as elucidated using SEM lead to postulation of polymer formation mechanism.     

The influence of cocatalysts on 1-hexene polymerization with various supported magnesium – titanium catalysts

Summary The influence of various cocatalysts on the activity and stereospecificity of a supported magnesium–titanium catalyst, generated by in situ reduction of titanium (IV) chloride using a Grignard reagent (MgCl₂/TiCl₃) or prepared by the recrystallization method (MgCl₂/2M2P/ED/TiCl₄, 2M2P= 2-methyl-2-pentanol, ED= dibutyl phthalate or ethyl benzoate), in the 1-hexene polymerization was investigated. The MgCl₂/TiCl₃ catalyst showed the highest activity but the lowest stereospecificity in the 1-hexene polymerization with all investigated cocatalysts. The MgCl₂/2M2P/ED/TiCl₄ catalyst with dibutyl phthalate as an internal electron donor was characterized by the highest stereospecificity and led to the polymers with high molecular weight. All catalysts showed the highest activity and stereospecificity when triisobutylaluminium was used as a cocatalyst. The addition of a small amount of ethyl benzoate as an external electron donor ([Al]/[ED] 10:1) led to considerable improvement of the stereospecificity of the MgCl₂/TiCl₃ catalyst in comparison with the catalysts prepared by the recrystallization method.     

Modification of Ziegler-Natta catalysts by cyclopentiadienyl-type ligands: Activation of titanium-based catalysts

Conventional Ziegler-Natta catalysts, based on TiCl₄ supported on MgCl₂, were modified by substituting a part of the chlorides by cyclopentadienyl (and derivatives) ligands. Although these catalysts are very active (activities up to 10⁵ g PE/g catalyst/h) they exhibit a conventional Ziegler-Natta behavior (methylaluminoxane is not necessary, polyethylene produced with a rather broad molar weight distribution, low sensitivity to hydrogen). It was attributed to cluster effects: an increase of the number of conventional TiCl₄ active sites by adding cyclopentadienyl ligands on titanium neighbors. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2281–2288, 1997     

Isospecific polymerization of vinyl ethers with titanium catalysts containing modified tridentate anionic donor ligands

BACKGROUND: Stereo‐regulated polymerization of vinyl ethers (VEs) assumes significance because of its elegance and the resultant unique polymer properties. Although several Lewis acid catalysts polymerize VEs with good control of molecular weight, achieving stereo‐regularity is quite challenging. There are literature reports of a few catalyst systems capable of producing highly isotactic poly(vinyl ether) (PVE) only at lower temperatures with the polymer becoming atactic with an increase in reaction temperature. Hence innovating new catalyst systems which can produce highly stereo‐regular PVEs with high molecular weight at ambient temperature is quite challenging. RESULTS: We used two different titanium pre‐catalysts (1‐TiCl₂ and 2‐TiCl₂) for the polymerization of VEs. These pre‐catalysts in combination with methylaluminoxane (MAO)/borate polymerized VEs in higher conversions. Highly isotactic poly(n‐butylvinyl ether) (PBVE; 75% dyad isotactic ratio) was obtained with 1‐TiCl₂/MAO at ambient temperature. CONCLUSION: We synthesized unimodal and highly isotactic PBVE with molecular weights of the order of 10⁵ g mol^?1 using the non‐metallocene‐type single‐site catalyst system 1‐TiCl₂/MAO even at ambient temperature. The symmetry around the metal centre in the pre‐catalyst and the polymerization temperature played a major role in controlling the stereo‐regularization of the olefin inserted. Copyright © 2009 Society of Chemical Industry     

Preparation and Characterization of Pt/C and Pt/TiO2 Electrocatalysts by Liquid Phase Photodeposition

The preparation of carbon and titanium dioxide supported Pt catalysts through a photochemical and photocatalytic routes were investigated. The catalysts were prepared by irradiation with UV-light (365 nm) at room temperature using H₂PtCl₆ and C₁₀H₁₄O₄Pt (Pt(acac)₂) as platinum precursors. The kinetic studies revealed that H₂PtCl₆ produced metallic platinum faster than Pt(acac)₂ and also showed that the amount of platinum deposited on TiO₂ was higher than on carbon. The samples were characterized by X-ray diffraction, SEM/EDS and cyclic voltammetry. X-ray diffraction permitted to identify the crystallographic (111) and (200) planes from platinum metal on the catalysts synthesized, the intensity of peaks depends of the amount of platinum deposited. SEM/EDS test confirmed what it was found by the kinetics studies. The electrocatalytic activity was compared with a commercial Pt E-Tek catalyst (10 wt%). The electrochemical results showed that Pt/C-AA catalyst synthesized by liquid phase photo-deposition method has stability in acid media and high distribution of the actives sites on the electrode surfaces. It could be considered as a candidate for electro-catalyst for polymer electrolyte fuel cell. The Pt/TiO₂ catalysts did not present electrochemical activity.     

Hydrogenation of CO<Subscript>2</Subscript> to methanol over Au–CuO/SBA-15 catalysts

A series of Au–CuO/SBA-15 catalysts with 1–3 wt% Au and 30 wt% CuO were successfully prepared for CO₂ hydrogenation to methanol by chemical reduction and the following impregnation. The influence of Au content on the physicochemical properties of Au–CuO/SBA-15 catalysts was investigated in terms of ICP-AES, N₂ physisorption, XRD, TEM, N₂O titration, XPS and H₂–TPR technique. The results showed that the as-prepared Au–CuO/SBA-15 catalysts exhibited higher catalytic activity than CuO/SBA-15 catalyst. 2 % Au–CuO/SBA-15 catalyst showed the best catalytic activity with 13.5 % methanol selectivity and 24.2 % CO₂ conversion for CO₂ hydrogenation to methanol. The addition of Au NPs played an important role in improving the catalytic activity for CO₂ hydrogenation to methanol, which may be attributed to the interaction between Au and CuO.     

ZrO2/TiO2 nanofiber catalyst for effective liquefaction of agricultural wastes in subcritical methanol

ABSTRACT

Lignin liquefaction could be achieved under subcritical methanol; instead, the reported supercritical status using ZrO₂/TiO₂ nanofibers prepared by calcination of poly(vinyl-acetate)/titanium isopropoxide/zirconium isopropoxide electrospun mats. ZrO₂ content in the final nanofibers has been adjusted at 0, 25, 50, 75 and 100 wt%. The nanofibers having 75 wt% ZrO₂ showed the best catalytic activity toward lignin liquefaction, 57.1 wt% weight losses at 180°C. The results indicated that 2 h and 15 wt% are the optimum holding time and catalyst content, respectively. Liquefaction of sawdust was performed; more than 60 wt% of the solid waste was converted to simple alcohols at 300°C (supercritical conditions).     

Comparison of ethylene-propylene copolymers obtained with Ti,V and Zr catalyst systems

Summary Ethylene and propylene were copolymerized in n-heptane in the presence of high activity heterogeneous MgCl₂/TiCl₄ catalyst and homogeneous VOCl₃ and Cp₂ZrCl₂ catalysts to study the effect on the catalyst to the microstructure and molecular weight distribution of the copolymer. The copolymer obtained with the zirconium catalyst was much more random in structure than that obtained with the vanadium and titanium catalysts and the molecular weight distribution was very narrow. Ethylene and propylene were also copolymerized in liquid propylene with MgCl₂/TiCl₄ and VOCl₃ catalyst systems. These copolymers were column fractionated and the fractions were analysed by NMR spectroscopy and DSC. The fractions of the copolymer obtained with the titanium catalyst was found to have broader distribution in composition than the copolymer obtained with the vanadium catalyst. This probably explains the traces of crystallinity in the copolymer prepared with the titanium catalyst. However, no effect was seen on the glass transition temperature.     

Comparative study of propylene polymerization using monosupported and bisupported titanium‐based Ziegler–Natta catalysts

Heterogeneous Ziegler–Natta systems—MgCl₂ (ethoxide type)/TiCl₄/di‐n‐butyl phthalate (DNBP)/triethylaluminum (TEA)/dimethoxymethylcyclohexylsilane (DMMCHS) and SiO₂/MgCl₂ (ethoxide type)/TiCl₄/DNBP/TEA/DMMCHS—were studied for the polymerization of propylene. The slurry polymerization of propylene was carried out with the catalyst systems in n‐heptane. Both systems performed with optimum activity at a particular [Al]/[DMMCHS]/[Ti] molar ratio. The ratio to reach the highest activity was much lower for the bisupported catalyst system. The productivity of the bisupported catalyst was higher than that of the monosupported one. Polypropylene of a high isotacticity index (II; >96%) was obtained with both systems and did not significantly change with an increasing [Al]/[DMMCHS]/[Ti] molar ratio. The addition of hydrogen as a chain‐transfer agent reduced II of the polymers obtained with both systems. The effect of the polymerization temperature (40–75°C) on the viscosity‐average molecular weight (M_v) and II showed a decrease in both cases. The bisupported catalyst system produced a polymer with higher M_v. The effect of temperature on II was similar for both the monosupported and bisupported systems. A monomer pressure of 2.02 × 10⁵ to 0.8 × 10⁶ Pa increased M_v of the obtained polymer. II of the polymer slightly decreased with increasing monomer pressure. The titanium content of the catalyst was 1.70 and 3.55% for the monosupported and bisupported systems, respectively. The surface area of the bisupported catalyst was higher than that of the monosupported catalyst. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2220–2226, 2006     

Hybrid titanium catalyst supported on core‐shell silica/poly(styrene‐co‐acrylic acid) carrier

Hybrid titanium catalysts supported on silica/poly(styrene‐co‐acrylic acid) (SiO₂/PSA) core‐shell carrier were prepared and studied. The resulting catalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, laser scattering particle analyzer and scanning electronic microscope (SEM). The hybrid catalyst (TiCl₃/MgCl₂/THF/SiO₂·TiCl₄/MgCl₂/PSA) showed core‐shell structure and the thickness of the PSA layer in the two different hybrid catalysts was 2.0 μm and 5.0 μm, respectively. The activities of the hybrid catalysts were comparable to the conventional titanium‐based Ziegler‐Natta catalyst (TiCl₃/MgCl₂/THF/SiO₂). The hybrid catalysts showed lower initial polymerization rate and longer polymerization life time compared with TiCl₃/MgCl₂/THF/SiO₂. The activities of the hybrid catalysts were enhanced firstly and then decreased with increasing P/P. Higher molecular weight and broader molecular weight distribution (MWD) of polyethylene produced by the core‐shell hybrid catalysts were obtained. Particularly, the hybrid catalyst with a PSA layer of 5.0 μm obtained the longest polymerization life time with the highest activity (2071 kg PE mol^?1 Ti h^?1) and the resulting polyethylene had the broadest MWD (polydispersity index = 11.5) under our experimental conditions. The morphology of the polyethylene particles produced by the hybrid catalysts was spherical, but with irregular subparticles due to the influence of PSA layer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Catalytic activity and control of the nascent morphology of polyethylenes obtained with first and second generation of Ziegler–Natta catalysts

The morphologies of the as-produced polyethylenes obtained by slurry polymerization process of ethylene in n-heptane, using heterogeneous conventional and supported Ziegler–Natta catalysts, were investigated. The ability of four different catalytic systems in controlling the size and shape of the nascent polymer particles were tested. The catalytic systems employed were: the original Ziegler type catalyst produced by reduction of TiCl₄ with Et₂AlCl, the Natta type catalyst TiCl₃–AA, the reduced TiCl₄ with the metal carbonyls [Mo(CO)₆ and Mn₂(CO)₁₀], and the supported TiCl₄ on three commercial silicas having different surface areas: Davison 951, 952, and also the Dart 1000. It was found that the carriers affect the catalytic activity of the final catalyst and also its kinetic behavior. The supported Ziegler–Natta catalysts control more easily the nascent polymer particles (size, shape, and porosity) than the conventional ones. In addition the morphology of the catalysts and the subsequent polymer particles are closely related to the parent morphology of the silicas used as carriers. Furthermore, the nascent morphology of the polyethylenes obtained with the conventional TiCl₄–Et₂AlCl catalytic system can be modified by using different |Al|/|Ti| ratios, resulting in more dense, spherical, and bigger polymer particles by increasing this ratio. On the other hand, detailed studies on the texture or arrangement of the polymer particles reveal the existence of mainly two fine morphologies (globular and wormlike), which are the result of the order of the primary or elementary catalyst particles (microspheres and platelets), the force linking them together, and the activity of the polymerization centers placed on their surface.     

Synthesis mechanisms of poly[styrene‐co‐(acrylic acid)]‐supported TiCl4 catalysts modified by magnesium compounds

Soluble poly[styrene‐co‐(acrylic acid)] (PSA) modified by magnesium compounds was used to support TiCl₄. For ethylene polymerization, four catalysts were synthesized, namely PSA/TiCl₄, PSA/MgCl₂/TiCl₄, PSA/(n‐Bu)MgCl/TiCl₄, and PSA/(n‐Bu)₂Mg/TiCl₄. The catalysts were characterized by a set of complementary techniques including X‐ray photoelectron spectroscopy, Fourier‐transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, and element analysis. Synthesis mechanisms of polymer‐supported TiCl₄ catalysts were proposed according to their chemical environments and physical structures. The binding energy of Ti 2p in PSA/TiCl₄ was extremely low as TiCl₄ attracted excessive electrons from ? COOH groups. Furthermore, the chain structure of PSA was destroyed because of intensive reactions taking place in PSA/TiCl₄. With addition of (n‐Bu)MgCl or (n‐Bu)₂Mg, ? COOH became ? COOMg‐ which then reacted with TiCl₄ in synthesis of PSA/(n‐Bu)MgCl/TiCl₄ and PSA/(n‐Bu)₂Mg/TiCl₄. Although MgCl₂ coordinated with ? COOH first, TiCl₄ would substitute MgCl₂ to coordinate with ? COOH in PSA/MgCl₂/TiCl₄. Due to the different synthesis mechanisms, the four polymer‐supported catalysts correspondingly showed various particle morphologies. Furthermore, the polymer‐supported catalyst activity was enhanced by magnesium compounds in the following order: MgCl₂ > (n‐Bu)MgCl > (n‐Bu)₂Mg > no modifier. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Catalytic activity of mesoporous V/SBA-15 in the transesterification and esterification of fatty acids

Mesoporous V/SBA-15 with different weight percentages (1, 2.5 and 5 wt%) of vanadia was prepared via the wet impregnation method. The mesoporous nature of the catalysts were investigated, using the X-ray diffraction analysis, N₂ adsorption–desorption isotherm and scanning electron microscope. All the catalysts showed the highly dispersed vanadia was confirmed by the result of the diffuse reflectance UV vis technique. From the NH₃-temperature programmed desorption, it is observed that, the acidity values of the prepared catalysts are in the range 72–102 µmol/g. 5 % V/SBA-15, possesses Bronsted and Lewis acid sites ensured by pyridine-adsorbed Fourier-transform infrared method. The acidity of the catalyst was experimented in the transesterification of sunflower oil. The reaction conditions were optimized with maximum conversion (100 %) of sunflower oil into biodiesel and the activity of the catalyst was found to be more in 5 wt% V/SBA-15 at 140 °C. Different fatty acids like butyric, valeric, caprylic and oleic acid were also studied under optimized conditions, and the isolated product was confirmed from the H¹ NMR spectroscopy.     

Heterogeneity of active sites of Ziegler‐Natta catalysts: The effect of catalyst composition on the MWD of polyethylene

Experimental data on the molecular weight distribution (MWD) of polyethylene (PE) produced over a broad number of Ziegler‐Natta catalysts differing in composition and preparation procedure are presented. These catalysts include nonsupported TiCl₃ catalyst, four types of supported titanium‐magnesium catalysts (TMC) differing in the content of titanium and the presence of various modifiers in the composition of the support, and a supported catalyst containing VCl₄ as an active component instead of TiCl₄. The studied catalysts produce PE with different molecular weights within a broad range of polydispersity (M_w/M_n = 2.8–16) under the same polymerization conditions. The heterogeneity of active sites of these catalysts was studied by deconvolution of experimental MWD curves into Flory components assuming a correlation between the number of Flory components and the number of active site types. Five Flory components were found for PE produced over nonsupported TiCl₃ catalysts (M_w/M_n = 6.8), and three–four Flory components were found for PE produced over TMC of different composition. A minimal number of Flory components (three) was found for PE samples (M_w/M_n values from 2.8 to 3.3) produced over TMC with a very low titanium content (0.07 wt %) and TMC modified with dibutylphtalate. It was shown that five Flory components are sufficient to fit the experimental MWD curve for bimodal PE (M_w/M_n = 16) produced over VMC. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface science studies of Ziegler-Natta olefin polymerization system: Correlations between polymerization kinetics, polymer structures, and active site structures on model catalysts

The surface composition and structure of model Ziegler-Natta catalysts, polymerizing α-olefins to produce polyolefins, have been studied using modern surface science techniques and compared with their polymerization behaviors. Two types of thin films — TiCl_x/MgCl₂ and TiCl_y/Au — were fabricated on an inert gold substrate, using chemical vapor deposition methods, to model the high-yield catalysts of MgCl₂-supported TiCl₄ and TiCl₃-based catalysts, respectively. The model catalysts could be activated by exposure to triethylaluminum (AlFt₃) vapor. Once activated, both catalysts were active for polymerization of ethylene and propylene in the absence of excess AlEt₃ during polymerization. The model catalysts had polymerization activities comparable to the high-surface-area industrial catalysts. Though both catalysts were terminated with chlorine at the surface, each catalyst assumed different surface structures. The TiCl_x/MgCl₂ film surface was composed of two structures: the (001) basal plane of these halide crystallites and a non-basal plane structure. The TiCl_y/Au film surface assumed only the non-basal plane structure. These structural differences resulted in different tacticity of the polypropylene produced with these catalysts. The TiCl_x/MgCl₂ catalyst produced both atactic and isotactic polypropylene, while the TiCl_y/Au catalyst without the MgCl₂ support produced exclusively isotactic polypropylene. The titanium oxidation state distribution did not have a critical role in determining the tacticity of the polypropylene.     

Effect of Raw Multi-Wall Carbon Nanotubes on Morphology and Separation Properties of Polyimide Membranes

Raw multi wall carbon nanotubes (r-MWCNTs) were embedded as fillers inside the polyimide (PI) matrix and PI/r-MWCNTs mixed matrix membranes were fabricated by the phase inversion method. The TEM images and permeation results using helium as test gas showed that r-MWCNTs were generally closed ended and acted as impermeable nano particles. Gas permeation tests using CO₂ and CH₄ showed that the addition of r-MWCNTs into the dope solution increased the CO₂/CH₄ separation factor while decreasing the carbon dioxide and methane permeances. When the r-MWCNTs content was increased from 0% to 6 wt.%, permeance of CO₂ in the flat sheet mixed matrix membranes decreased from 9.15 GPU to 5.49 GPU and CO₂/CH₄ separation factor increased from 19.05 to 45.75. Identical to flat sheet mixed matrix membranes, the addition of 2 wt.% r-MWCNTs into a spinning dope increased the CO₂/CH₄ separation factor from 46.61 to 72.20. The glass transition temperature of the mixed matrix flat sheet membranes increased with an increase in the r-MWCNTs content. This implies a good segmental-level attachment between the two phases that forms a rigidified polymer region at the polymer/r–MWCNTs interface. FESEM images showed well dispersed r-MWCNTs in the polymer matrix at a loading of 2 wt% r-MWCNTs.     

Preparation and characterization of novel polyethylene/carbon nanotubes nanocomposites with core–shell structure

Preparation of novel polyethylene/carbon nanotubes (CNTs) nanocomposites with core–shell structure was presented. The method involved in situ ethylene polymerization in which nanotube surface was treated with Grignard Agent, followed by reacting with active transition metal compound, TiCl₄. The multiwalled carbon nanotubes (MWCNTs) supported catalysts polymerize ethylene to form polymer nanocomposite. MWCNTs were homogeneously dispersed within polymer matrix, and as expected, the resultant nanocomposites featured core–shell structure which was confirmed by HRTEM. For the nanocomposite, the microscopic examination of the cryogenically fractured surface not only ensured a good distribution of carbon nano-particles in the PE matrix but also revealed the ductile-like fracture. The Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed for the study of covalent sidewall functionalization and chemical bonding environment of MWCNTs, also indicated effective immobilization of titanium catalyst on the MWCNTs surface. The crystalline properties, dielectric property and thermal stability of the nanocomposites were determined by WAXD, impedance analyzer and TGA. The dielectric result showed a slight decline of the dielectric constant of the nanocomposites with increase of the polymerization time, and lower dielectric loss was also observed.     

Ring opening metathesis polymerization of dicyclopentadiene catalyzed by titanium tetrachloride adduct complexes with nitrogen‐containing ligands

Ring opening metathesis polymerization (ROMP) of dicyclopentadiene (DCPD) catalyzed by titanium tetrachloride adduct complexes such as TiCl₄ · 2L [L = pyridine (1), 2‐methylpyridine (2), 2,4,6‐trimethylpyridine (3), 3‐aminopyridine (4), 2‐hyroxypyridine (5)] and CH₃Li as cocatalyst was reported. The polymer was characterized by IR and ¹H‐NMR methods. Five influencing factors were also discussed. The catalyst systems TiCl₄ · 2L/CH₃Li (L = 2‐methylpyridine, 2,4,6‐trimethylpyridine) appeared to be very active for the ROMP of DCPD. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3247–3251, 2000