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Shigetaka Hayano - One of the best experts on this subject based on the ideXlab platform.
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Iso- and Syndio-Selective ROMP of Norbornene and Tetracyclododecene: Effects of Tacticity Control on the Hydrogenated Ring-Opened Poly(cycloolefin)s
2014Co-Authors: Shigetaka Hayano, Yuki NakamaAbstract:Isospecific and syndioselective ring-opening metathesis Polymerizations (ROMP) of norbornene (NB) and tetracyclododecene (TCD), as well as their tactic (and Atactic) hydrogenated ring-opened Polymer products have been thoroughly investigated for the first time. In the case of NB Polymerization, cis-isospecific ROMPs of NB were achieved with Mo(O)(rac-5,5′,6,6′-Me4-3,3′-t-Bu2-biphenolate)2-based catalyst (cis = 100%, isotacticity =100%). Cis-syndioselective ROMPs of NB proceeded in the presence of W(NPh)Cl4·Et2O- and W(N-2,6Me2Ph)Cl4·Et2O-based catalysts (cis = 90%, syndiotacticity =90%). Hydrogenated poly(NB)s exhibited high crystallinity irrespective of their stereostructures. The crystalline nature of syndiotactic hydrogenated poly(NB) (syndiotacticity = 90%: Tm = 130–136 °C, ΔH = 60–75 J/g, wc = 0.55–0.70) was close to that of conventional Atactic one (meso/racemo = 50/50: Tm = 145–150 °C, ΔH = 65–70 J/g, wc = 0.65). On the contrary, isotactic hydrogenated poly(NB) was characterized by a remarkably unique crystalline nature such as high melting points (isotacticity > 90%: Tm = 160–180 °C, ΔH = 50–90 J/g, wc = 0.50–0.65). In the case of TCD Polymerization, W(NPh)Cl4·Et2O-based catalyst introduced cis-syndioselective ROMP of TCD (cis = 90%, syndiotacticity = 86%). Syndiotactic hydrogenated poly(TCD) obtaining from W(NPh)Cl4·Et2O-based catalyst was entirely amorphous and soluble in ordinary organic solvents. On the other hand, Atactic hydrogenated poly(TCD) showed poor solubility and semicrystallinity (Tm = 290 °C, ΔH < 10 J/g). In addition, Mo(O)(rac-5,5′,6,6′-Me4-3,3′-t-Bu2-biphenolate)2-based catalyst provided all-cis poly(TCD), of which hydrogenated product was completely insoluble and highly crystalline (Tm > 350 °C, wc = 0.65). These tendencies are in significant contrast to those of the hydrogenated poly(endo-dicyclopentadiene)s, wherein Atactic Polymer is amorphous and both tactic Polymers are crystalline (syndiotacticity = 90%; Tm = 270 °C and isotacticity > 95%; Tm = 295 °C, respectively)
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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 ...
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 ...
Yoshio Okamoto - One of the best experts on this subject based on the ideXlab platform.
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stereospecific radical Polymerization of α alkoxymethyl acrylates controlled by lewis acid catalysts mechanistic study and effect of amino alcohols as ligand for zinc bromide
Macromolecules, 2001Co-Authors: Hideo Baraki, Shigeki Habaue, Yoshio OkamotoAbstract:The stereospecific radical Polymerization of methyl and benzyl α-(methoxymethyl)acrylates was performed in the presence of Lewis acids, such as ZnBr2 and Sc(OTf)3. The stereochemistry of the Polymerization was significantly affected by the coordination of the Lewis acids to the polar groups of the monomer and Polymer. The Polymerization systems in the presence of ZnBr2 and Sc(OTf)3 produced syndiotactic- and isotactic-rich Polymers, respectively, showing different ESR signals. When amino alcohols were added to the Polymerization system with ZnBr2, heterotactic-rich Polymers were obtained. Therefore, syndiotactic-, isotactic-, and heterotactic-rich Polymers can be synthesized by the radical method in the presence of a catalytic amount of ZnBr2, Sc(OTf)3, and the ZnBr2−amino alcohol complex, respectively, without changing the other Polymerization conditions, although an Atactic Polymer was produced in the absence of a Lewis acid. The detailed tacticity (tetrad) of the obtained Polymer was estimated by 13C N...
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stereospecific Polymerization of benzyl α alkoxymethyl acrylates
Journal of Polymer Science Part A, 1997Co-Authors: Shigeki Habaue, Hiroshi Yamada, Takahiro Uno, Yoshio OkamotoAbstract:a-(Alkoxymethyl)acrylates, such as methyl α-(phenoxymethyl)acrylate, benzyl α-(methoxymethyl) acrylate (BMMA), benzyl α-(benzyloxymethyl) acrylate, and benzylα-(tert-butoxymethyl)acrylate, were synthesized, and their Polymerizability and the stereoregularity of the Polymers obtained by radical and anionic methods were investigated. The radically obtained Polymers were found to be Atactic by 13 C- and 1 H-NMR analyses, but the Polymers obtained with lithium reagents in toluene at -78°C were highly isotactic. Further, it is noteworthy that isotactic Polymers were also produced with lithium reagents even in tetrahydrofuran. Effects of Polymerization temperature and counter cation on stereoregularity were clearly observed in the Polymerization of BMMA, and a potassium reagent afforded an almost Atactic Polymer.
Collar, Emilia P. - One of the best experts on this subject based on the ideXlab platform.
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The Role of a Succinyl Fluorescein-Succinic Anhydride Grafted Atactic Polypropylene on the Dynamic Mechanical Properties of Polypropylene/Polyamide-6 Blends at the Polypropylene Glass Transition
'MDPI AG', 2020Co-Authors: García-martínez, Jesús María, Collar, Emilia P.Abstract:© 2020 by the authors.The present article adequately supports a twofold objective. On one hand, the study of the dynamic mechanical behavior of polypropylene/polyamide-6 blends modified by a novel compatibilizer was the objective. This was previously obtained by chemical modification of an Atactic polypropylene Polymerization waste. On the other hand, the accurate predictions of these properties in the experimental space scanned was the objective. As a novelty, this compatibilizer contains grafts rather than just maleated ones. Therefore, it consists precisely of an Atactic Polymer containing succinic anhydride (SA) bridges and both backbone and terminal grafted succinyl-fluorescein groups (SFSA) attached to the Atactic backbone (aPP-SFSA). Therefore, it contains 6.2% of total grafting (2.5% as SA and 3.7% as SF), which is equivalent to 6.2 × 10−4 g·mol−1. This interfacial agent was uniquely designed and obtained by the authors themselves. Essentially, this article focuses on how the beneficial effect of both PA6 and aPP-SFSA varies the elastic (E’) and the viscous (E’’) behavior of the iPP/aPP-SFSA/PA6 blend at the iPP glass transition. Thus, we accurately measured the Dynamic Mechanical Analysis (DMA) parameters (E’, E’’) at this specific point considering it represents an extremely unfavorable scenario for the interfacial modifier due to mobility restrictions. Hence, this evidences the real interfacial modifications caused by aPP-SFSA to the iPP/PA6 system. Even more, and since each of the necessary components in the blend typically interacts with one another, we employed a Box–Wilson experimental design by its marked resemblance to the “agent-based models”. In this manner, we obtained complex algorithms accurately forecasting the dynamic mechanical behavior of the blends for all the composition range of the iPP/aPP-SFSA/PA6 system at the glass transition of iPP.The results discussed at present work were partially obtained under the auspices of the MAT 2000-1499 and MAT2013-47902-C2-1-R Research Projects.Peer reviewe
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The effect of a succinic anhydride/succinil-fluoresceine grafted Atactic polypropylene on polypropylene/polyamide 6 blends at the polypropylene glass transition as revealed by dynamic mechanical analysis
'AIP Publishing', 2019Co-Authors: García-martínez, Jesús María, Taranco Jesús, Areso S., Collar, Emilia P.Abstract:This work deals with a dynamic mechanical analysis study on the effect of a novel interfacial agent containing grafts rather than maleated ones, in all the compositional spectra of the iPP/PA6 system. The interfacial agent used is an Atactic Polymer (from Polymer wastes) with succinic bridges and both backbone and terminal grafted succinil fluoresceine groups (aPP-SF/SA) containing 6.2 % of total grafted groups (2.5% SA and 3.7% SF), equivalent to 6.2 ·10-4¿g.mol¿1, obtained at the authors¿ labs. The effects of both PA6 and aPP-SFSA cause changes in the glass transition temperature (Tg) of iPP in the blend. One of the novelties of the work is introducing an interfacial agent with other groups rather than only maleic anhydride, capable to modify the behavior of the system in a positive, and very different manner, than raditional maleated agents. This has let a better understanding of the interphase between components. In this work we have used dynamic mechanical parameters to evidence the interfacial modifications caused by the presence of aPP-SF/SA in the iPP/PA6 system at the iPP Tg. Besides, by considering each component of the blend as interacting each other, we have used a Box-Wilson model by resembling the so called ¿agent based models¿ to obtain algorithms capable to make forecasts of the dynamic mechanical parameters (storage, E¿, and loss moduli, E¿¿, at the glass transition of iPP, in all the composition range of whatever iPP/PA6/aPP-SFSA modified blend.Peer Reviewe
Richard A. Register - One of the best experts on this subject based on the ideXlab platform.
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Hydrogenated ring-opened polynorbornene: A highly crystalline Atactic Polymer
Macromolecules, 2005Co-Authors: Li Bong W. Lee, Richard A. RegisterAbstract:Ring-opening metathesis Polymerization (ROMP) of norbornene with most catalysts produces a Polymer with an Atactic placement of the cyclopentylene rings, yet partial hydrogenation of this Polymer is known to yield a crystalline product. We report here a facile catalytic route to saturate polynorbornene (PN); fully hydrogenated polynorbornene (hPN) is highly crystalline, with an equilibrium melting point estimated as 156 °C. The crystal lattice is monoclinic, with parameters a = 6.936 A, b = 9.596 A, c = 12.420 A, and β = 130.7° at room temperature, indicating nearly complete extension of the hPN backbone within the unit cell. The material remains highly crystalline until the melting point is reached, but near 105 °C, the crystal structure transforms to one characterized by substantial rotational disorder of the hPN chains about their axes, while retaining substantial translational order.