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Shigetaka Hayano - One of the best experts on this subject based on the ideXlab platform.
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hydrogenated ring opened poly endo Dicyclopentadiene s made via stereoselective romp catalyzed by tungsten complexes crystalline tactic polymers and amorphous atactic polymer
Macromolecules, 2006Co-Authors: Shigetaka Hayano, Yoshihisa Takeyama, Yasuo Tsunogae, Ichiro IgarashiAbstract:Properties of the tactic and atactic hydrogenated ring-opened poly(endo-Dicyclopentadiene)s and features of the tungsten imido/phenolate-catalyzed stereoselective ring-opening metathesis polymerizations (ROMP) were studied. Several tungsten(VI) imido phenolate complexes were synthesized and exhibited moderate ROMP activity in the presence of n-BuLi. W(NPh)((R)-(+)-5,5‘,6,6‘-Me4-3,3‘-t-Bu2-biphenolate)2 was found to be effective for cis-, isoselective ROMP of endo-Dicyclopentadiene (DCPD), while W(NPh)Cl4·Et2O promoted cis-, syndioselective ROMP. On the other hand, W(NPh)(2,6-Me2-phenolate)4 provided atactic poly(DCPD). Isotactic, atactic, and syndiotactic hydrogenated ring-opened poly(DCPD)s were characterized well by various methods for the first time. Both tactic polymers were shown to be crystalline polymers by means of DSC, WAXD, and TEM measurements. In contrast, atactic poly(DCPD) was an amorphous polymer. The crystallization rate of the syndiotactic hydrogenated poly(DCPD) was significantly higher ...
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stereospecific ring opening metathesis polymerization of cycloolefins using novel molybdenum and tungsten complexes having biphenolate ligands development of crystalline hydrogenated poly endo Dicyclopentadiene and poly norbornene
Macromolecules, 2003Co-Authors: Shigetaka Hayano, Yasuo Tsunogae, Hiroshi Kurakata, Yuushou Nakayama, Yoshinori Sato, Hajime YasudaAbstract:Novel molybdenum- and tungsten-based catalysts induced stereospecific ring-opening metathesis polymerization (ROMP) of cycloolefins to produce a new class of crystalline polymers. Various monomeric molybdenum(VI) and tungsten(VI) complexes of the general formula M(=O)(O−Ar)4 (M = Mo or W; (O−Ar)4 is two biphenolate or four phenolate ligands) were prepared. These catalysts exhibited moderate ROMP activity in the presence of cocatalyst such as n-BuLi and Et3Al. The molybdenum and tungsten complexes bearing substituted biphenolate ligands such as oxomolybdenum(VI) bis(racemic-5,5‘,6,6‘-tertamethyl-3,3‘-di-tert-butyl-1,1‘-biphenyl-2,2‘-diolate) promoted cis and isospecific ROMP of endo-Dicyclopentadiene (cis > 90% and meso > 95%). The novel ternary and quarternary catalysts such as MoOCl4−biphenolate−n-BuLi (1:2:2) were developed as a new useful methodology to control the stereoselectivity of the ROMP. Hydrogenation of the cis-isotactic poly(endo-Dicyclopentadiene)s and poly(norbornene)s provided novel crysta...
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stereospecific ring opening metathesis polymerization of endo Dicyclopentadiene by schrock hoveyda catalyst and novel mo and w based complexes development of crystalline hydrogenated poly endo Dicyclopentadiene
Chemistry Letters, 2003Co-Authors: Shigetaka Hayano, Yasuo Tsunogae, Hiroshi Kurakata, Daisuke Uchida, Masato Sakamoto, Naoya Kishi, Hirokazu Matsumoto, Ichiro IgarashiAbstract:Novel crystalline polymer, crystalline hydrogenated poly(endo-Dicyclopentadiene), was developed on the basis of the development of new cis- and iso-specific ROMP catalysts such as MoO(rac-5,5′,6,6′...
Chunshan Wang - One of the best experts on this subject based on the ideXlab platform.
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flame retardancy and dielectric properties of Dicyclopentadiene based benzoxazine cured with a phosphorus containing phenolic resin
Journal of Applied Polymer Science, 2008Co-Authors: Hannjang Hwang, Chunshan WangAbstract:A Dicyclopentadiene-based benzoxazine (DCPDBZ) was prepared and separately copolymerized with melamine–phenol formaldehyde novolac or phosphorus-containing phenolic resin (phosphorus-containing diphenol) at various molar ratios. Their curing behaviors were characterized by differential scanning calorimetry. The electrical properties of the cured resins were studied with a dielectric analyzer. The glass-transition temperatures were measured by dynamic mechanical analysis. The thermal stability and flame retardancy were determined by thermogravimetric analysis and a UL-94 vertical test. These data were compared with those of bisphenol A benzoxazine and 4,4′-biphenol benzoxazine systems. The effects of the diphenol structure and cured composition on the dielectric properties, moisture resistance, glass-transition temperature, thermal stability, and flame retardancy are discussed. The DCPDBZ copolymerized with phosphorus-containing novolac exhibited better dielectric properties, moisture resistance, and flame retardancy than those of the melamine-modified system. The flame retardancy of the cured benzoxazine/phosphorus-containing phenolic resins increased with increasing phosphorus content. The results indicate that the bisphenol A and 4,4′-biphenol systems with a phosphorus content of about 0.6% and the Dicyclopentadiene system with a phosphorus content of about 0.8% could achieve a flame-retardancy rating of UL-94 V-0. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
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low dielectric epoxy resins from Dicyclopentadiene containing poly phenylene oxide novolac cured with Dicyclopentadiene containing epoxy
Reactive & Functional Polymers, 2008Co-Authors: Hannjang Hwang, Chia Lung Chung, Chunshan WangAbstract:Abstract Dicyclopentadiene-containing low molecular weight poly(phenylene oxide) (PPO) novolac (DCPD-PPO) was prepared by redistributing regular PPO with Dicyclopentadiene phenol novolac (DCPDNO), using benzoyl peroxide (BPO) as an initiator in toluene. The synthesized Dicyclopentadiene-containing redistributed-PPO novolac (DCPD-PPO) with terminal phenolic hydroxyl group and low molecular weight was used in the modification of Dicyclopentadiene containing epoxy (DCPD-epoxy)/4,4′-diamino-diphenylmethane (DDM) network system. The thermal and dielectric properties of the cured DCPD-PPO/DCPD-epoxy system were compared with those of bisphenol A containing DCPD-PPO/BPA-epoxy or BPA-PPO/DCPD-epoxy systems. In addition to, a higher glass transition temperature and thermal stability, the cured DCPD-PPO/DCPD-epoxy resins exhibit lower dielectric constant, dissipation factor, coefficient of thermal expansion and moisture absorption than those of bisphenol A based redistributed-PPO/epoxy.
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dielectric and thermal properties of Dicyclopentadiene containing bismaleimide and cyanate ester part iv
Polymer, 2006Co-Authors: Hannjang Hwang, Chunshan WangAbstract:A novel bismaleimide (BMI), bis(4-maleimidophenoxy-3,5-dimethylphenyl)Dicyclopentadiene (DCPDBMI), containing a large Dicyclopentadiene (DCPD) and aryl ether linkage, was synthesized from bis(4-aminophenoxy-3,5-dimethylphenyl)Dicyclopentadiene and maleic anhydride by the usual two-step procedure that included ring-opening addition to give bismaleamic acid, followed by cyclodehydration to bismaleimide. The monomers were characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (NMR), elemental analyses (EA), and mass spectra (MS). A series of bismaleimide-triazine (BT) resins were prepared from synthesized bismaleimide (DCPDBMI) and then cured with 2,6-dimethyl phenol-Dicyclopentadiene dicyanate ester (DCPDCY) at various molar ratios. Thermal properties of cured BT resins (DCPDBMI/DCPDCY) were studied using dielectric analyzer (DEA), dynamic mechanical analyzer (DMA) and thermalgravimetric analyzer (TGA). These data were compared with that of commercial bismaleimide (DDMBMI) cured with bisphenol A dicyanate ester (BADCY). The cured DCPDBMI/DCPDCY exhibits lower dielectric constant, dissipation factor and moisture absorption than those of DDMBMI/BADCY. The effects of blend composition on the glass transition temperatures and thermal stability are discussed.
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low dielectric thermoset i synthesis and properties of novel 2 6 dimethyl phenol Dicyclopentadiene epoxy
Journal of Applied Polymer Science, 2003Co-Authors: Ching-hsuan Lin, Jung Chung Chiang, Chunshan WangAbstract:A 2,6-dimethyl phenol-Dicyclopentadiene novolac was synthesized from Dicyclopentadiene and 2,6-dimethyl phenol, and the resultant 2,6-dimethyl phenol-Dicyclopentadiene novolac was epoxidized to 2,6-dimethyl phenol-Dicyclopentadiene epoxy. The structures of novolac and epoxy were confirmed by Fourier transform infrared spectroscopy (FTIR), elemental analysis, mass spectroscopy (MS), nuclear magnetic resonance spectroscopy (NMR), and epoxy equivalent weight titration. The synthesized 2,6-dimethyl phenol-Dicyclopentadiene epoxy was then cured with 4,4-diaminodiphenyl methane (DDM), phenol novolac (PN), 4,4-diaminodiphenyl sulfone (DDS), and 4,4-diaminodiphenyl ether (DDE). Thermal properties of cured epoxy resins were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), dielectric analysis (DEA), and thermal gravimetric analysis (TGA). These data were compared with those of the commercial bisphenol A epoxy system. Compared with the bisphenol A epoxy system, the cured 2,6-dimethyl phenol- Dicyclopentadiene epoxy resins exhibited lower dielectric constants (∼3.0 at 1 MHz and 2.8 at 1 GHz), dissipation factors (∼0.007 at 1 MHz and 0.004 at 1 GHz), glass transition temperatures (140–188°C), thermal stability (5% degradation temperature at 382–404°C), thermal expansion coefficients [50–60 ppm/°C before glass-transition temperature (Tg)], and moisture absorption (0.9–1.1%), but higher modulus (∼2 Gpa at 60°C). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2607–2613, 2003
Scott R. White - One of the best experts on this subject based on the ideXlab platform.
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Fracture and fatigue response of a self-healing epoxy adhesive
Polymer, 2011Co-Authors: G M Miller, Nancy R. Sottos, Scott R. WhiteAbstract:A self-healing epoxy adhesive for bonding steel substrates is demonstrated using encapsulated Dicyclopentadiene (DCPD) monomer and bis(tricyclohexylphosphine)benzylidine ruthenium (IV) dichloride (Grubbs’ first generation) catalyst particles dispersed in a thin epoxy matrix. Both quasi-static fracture and fatigue performance are evaluated using the width-tapered-double-cantilever-beam specimen geometry. Recovery of 56% of the original fracture toughness under quasi-static fracture conditions occurs after 24 h healing at room temperature conditions. Complete crack arrest is demonstrated for fatigue test conditions that render neat resin and control samples failed. Inspection of fracture surfaces by electron microscopy reveals evidence of polymerized DCPD after healing. These results are the first mechanical assessment of self-healing for thin (ca. 360 mm) films typical of adhesives applications.
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Life extension of self-healing polymers with rapidly growing fatigue cracks
Journal of the Royal Society Interface, 2007Co-Authors: A. S. Jones, Joseph D. Rule, Jeffrey S. Moore, Nancy R. Sottos, Scott R. WhiteAbstract:Self-healing polymers, based on microencapsulated Dicyclopentadiene and Grubbs' catalyst embedded in the polymer matrix, are capable of responding to propagating fatigue cracks by autonomic processes that lead to higher endurance limits and life extension, or even the complete arrest of the crack growth. The amount of fatigue-life extension depends on the relative magnitude of the mechanical kinetics of crack propagation and the chemical kinetics of healing. As the healing kinetics are accelerated, greater fatigue life extension is achieved. The use of wax-protected, recrystallized Grubbs' catalyst leads to a fourfold increase in the rate of polymerization of bulk Dicyclopentadiene and extends the fatigue life of a polymer specimen over 30 times longer than a comparable non-healing specimen. The fatigue life of polymers under extremely fast fatigue crack growth can be extended through the incorporation of periodic rest periods, effectively training the self-healing polymeric material to achieve higher endurance limits.
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catalyst morphology and dissolution kinetics of self healing polymers
Chemistry of Materials, 2006Co-Authors: A. S. Jones, Joseph D. Rule, Scott R. White, Jeffrey S. Moore, Nancy R. SottosAbstract:The role of the crystal morphology and dissolution kinetics of Grubbs' catalyst on self-healing capability is examined. Self-healing polymers require complete coverage of the crack plane with polymerized healing agent for optimal recovery of mechanical integrity. Lack of catalyst leads to incomplete coverage, partial polymerization, and poor mechanical recovery. Catalyst availability is determined by the competing rates of dissolution of the catalyst and polymerization of the healing agent. First-generation Grubbs' catalyst exists in at least two crystal polymorphs, each with a distinct crystal shape, thermal stability, and dissolution kinetics. The more rapidly dissolving polymorph shows superior healing efficiency when used as the initiator in a self-healing epoxy material based on ring-opening metathesis polymerization of Dicyclopentadiene.
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in situ poly urea formaldehyde microencapsulation of Dicyclopentadiene
Journal of Microencapsulation, 2003Co-Authors: E N Brown, Nancy R. Sottos, Michael R Kessler, Scott R. WhiteAbstract:Microencapsulated healing agents that possess adequate strength, long shelf-life and excellent bonding to the host material are required for self-healing materials. Urea-formaldehyde microcapsules containing Dicyclopentadiene were prepared by in situ polymerization in an oil-in-water emulsion that meet these requirements for self-healing epoxy. Microcapsules of 10–1000 μm in diameter were produced by appropriate selection of agitation rate in the range of 200–2000 rpm. A linear relation exists between log(mean diameter) and log(agitation rate). Surface morphology and shell wall thickness were investigated by optical and electron microscopy. Microcapsules are composed of a smooth 160–220 nm inner membrane and a rough, porous outer surface of agglomerated urea-formaldehyde nanoparticles. Surface morphology is influenced by pH of the reacting emulsion and interfacial surface area at the core-water interface. High yields (80–90%) of a free flowing powder of spherical microcapsules were produced with a fill co...
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cure kinetics of the ring opening metathesis polymerization of Dicyclopentadiene
Journal of Polymer Science Part A, 2002Co-Authors: Michael R Kessler, Scott R. WhiteAbstract:The cure kinetics of polyDicyclopentadiene prepared by ring-opening metathesis polymerization with three different concentrations of Grubbs' catalyst were examined with differential scanning calorimetry. The experimental data were used to test several different phenomenological kinetic models. The data were best modeled with a model-free isoconversional method. This analysis revealed that the activation energy increased significantly for degrees of cure greater than 60%. The catalyst concentration had a large effect on the cure kinetics. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2373–2383, 2002
Ichiro Igarashi - One of the best experts on this subject based on the ideXlab platform.
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hydrogenated ring opened poly endo Dicyclopentadiene s made via stereoselective romp catalyzed by tungsten complexes crystalline tactic polymers and amorphous atactic polymer
Macromolecules, 2006Co-Authors: Shigetaka Hayano, Yoshihisa Takeyama, Yasuo Tsunogae, Ichiro IgarashiAbstract:Properties of the tactic and atactic hydrogenated ring-opened poly(endo-Dicyclopentadiene)s and features of the tungsten imido/phenolate-catalyzed stereoselective ring-opening metathesis polymerizations (ROMP) were studied. Several tungsten(VI) imido phenolate complexes were synthesized and exhibited moderate ROMP activity in the presence of n-BuLi. W(NPh)((R)-(+)-5,5‘,6,6‘-Me4-3,3‘-t-Bu2-biphenolate)2 was found to be effective for cis-, isoselective ROMP of endo-Dicyclopentadiene (DCPD), while W(NPh)Cl4·Et2O promoted cis-, syndioselective ROMP. On the other hand, W(NPh)(2,6-Me2-phenolate)4 provided atactic poly(DCPD). Isotactic, atactic, and syndiotactic hydrogenated ring-opened poly(DCPD)s were characterized well by various methods for the first time. Both tactic polymers were shown to be crystalline polymers by means of DSC, WAXD, and TEM measurements. In contrast, atactic poly(DCPD) was an amorphous polymer. The crystallization rate of the syndiotactic hydrogenated poly(DCPD) was significantly higher ...
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stereospecific ring opening metathesis polymerization of endo Dicyclopentadiene by schrock hoveyda catalyst and novel mo and w based complexes development of crystalline hydrogenated poly endo Dicyclopentadiene
Chemistry Letters, 2003Co-Authors: Shigetaka Hayano, Yasuo Tsunogae, Hiroshi Kurakata, Daisuke Uchida, Masato Sakamoto, Naoya Kishi, Hirokazu Matsumoto, Ichiro IgarashiAbstract:Novel crystalline polymer, crystalline hydrogenated poly(endo-Dicyclopentadiene), was developed on the basis of the development of new cis- and iso-specific ROMP catalysts such as MoO(rac-5,5′,6,6′...
Christian Slugovc - One of the best experts on this subject based on the ideXlab platform.
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Variation of the Sterical Properties of the N‑Heterocyclic Carbene Coligand in Thermally Triggerable Ruthenium-Based Olefin Metathesis Precatalysts/Initiators
2015Co-Authors: Eva Pump, Karol Grela, Anita Leitgeb, Anna Kozłowska, Ana Torvisco, Laura Falivene, Luigi Cavallo, Christian SlugovcAbstract:A series of ruthenium complexes based on the κ2(C,N)-(2-(benzo[h]quinolin-10-yl)methylidene ruthenium dichloride fragment featuring different neutral coligands L (L = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene (SIPr), 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene (SIMes), 1,3-bis(2,4-dimethylphenyl)-4,5-dihydroimidazol-2-ylidene (SIXyl), and 1,3-bis(2-methylphenyl)-4,5-dihydroimidazol-2-ylidene (SITol)) was prepared, characterized, and tested in the thermally induced ring-opening metathesis polymerization of Dicyclopentadiene. In addition, the corresponding tricyclohexylphosphine derivative was investigated for comparison. All compounds were isolated as their trans-dichloro isomers. NMR spectroscopic features as well as structural features are, particularly within the NHC-bearing complexes, very similar, but their polymerization activity at elevated temperatures is distinctly different. While the SIMes derivative shows the desired properties, i.e., latency at room temperature and pronounced polymerization activity at elevated temperature, all other preinitiators do not. The preinitiator featuring the SIPr coligand is the most latent one, needing temperatures > 140 °C to show moderate activity in the polymerization of Dicyclopentadiene. Compounds bearing the smaller N-heterocyclic carbene congeners are stable and latent at room temperature, but decompose upon heating, diminishing the polymerization activity at elevated temperatures. Density functional calculations show that the SIMes derivative is the easiest to activate and yields the most stable 14-electron intermediate. Finally calculations reveal a distinct influence of the nature of the N-heterocyclic carbene ligand on the position of the equilibrium of cis- and trans-dichloro isomers of the complexes. While the SIPr and the SIMes derivatives prefer the cis-configuration, all other derivatives favor, at least in solvents with low dielectric constants, the trans-configuration. These computational findings were supported by the isolation and full characterization of the cis-dichloro isomer of the SIMes-bearing preinitiator obtained upon heating of its trans-isomer at 140 °C
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chelating ruthenium phenolate complexes synthesis general catalytic activity and applications in olefin metathesis polymerization
Chemistry: A European Journal, 2014Co-Authors: Anna Kozlowska, Christian Slugovc, Maciej Dranka, Janusz Zachara, Eva Pump, Krzysztof Skowerski, Karol GrelaAbstract:Cyclic Ru-phenolates were synthesized, and these compounds were used as olefin metathesis catalysts. Investigation of their catalytic activity pointed out that, after activation with chemical agents, these catalysts promote ring-closing metathesis (RCM), enyne and cross-metathesis (CM) reactions, including butenolysis, with good results. Importantly, these latent catalysts are soluble in neat Dicyclopentadiene (DCPD) and show good applicability in ring-opening metathesis polymeriyation (ROMP) of this monomer.
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ring opening metathesis polymerisation of emulsion templated Dicyclopentadiene giving open porous materials with excellent mechanical properties
Polymer Chemistry, 2012Co-Authors: Sebastijan Kovacic, Karel Jeřabek, Peter Krajnc, Christian SlugovcAbstract:Surfactant stabilized emulsions of Dicyclopentadiene and 50%, 60%, 70% or 80% of water were cured using ring opening metathesis polymerisation. All formulations gave open porous architectures featuring excellent mechanical properties which change upon oxidation.
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inherently reactive polyhipe material from Dicyclopentadiene
Chemical Communications, 2010Co-Authors: Sebastijan Kovacic, Peter Krajnc, Christian SlugovcAbstract:A simple formulation of a stable high internal phase emulsion of Dicyclopentadiene which is cured by using properly selected ring opening metathesis polymerization initiators yields highly porous monolithic materials with paramount mechanical properties and the possibility of easy functionalisation.