Search

Your search keyword '"Coughlin, E. Bryan"' showing total 331 results
Start Over Author "Coughlin, E. Bryan"
331 results on '"Coughlin, E. Bryan"'

109. Iso-specific Ziegler-Natta polymerization of alpha-olefins with a single-component organoyttrium catalyst

Author

Coughlin, E. Bryan and Bercaw, John E.

Subjects
Organic compounds -- Synthesis, Polymerization -- Research, Catalysts -- Research, Yttrium -- Research, Aromatic compounds -- Research, Chemistry
Abstract

The synthesis of rac-Me2Si(2-SiMe3-4-CMe3C5H2)2YR or (rac-BpYH)2 provides the firstiso-specific, single component Ziegler-Natta polymerization catalyst. (rac-BpYH)2 is obtained by addition of YCl3(THF)3 to LiBp, followed by deprotonation and removal of lithium chloride and tetrahydrofuran. The catalystis shown to effectively induce the polymerization of propylene, 1-butene, 1-pentene and 1-hexene into medium molecular weight (4,200-24,000) polymers.

Published
1992

116. Preface

Author

Theato, Patrick, primary, Kilbinger, Andreas F. M., additional, and Coughlin, E. Bryan, additional

Published
2011
Full Text
View/download PDF

118. Iso-specific Ziegler-Natta polymerization of α-olefins with a single-component organoyttrium catalyst

Author

Coughlin, E. Bryan

Subjects
Chemistry
Abstract

The synthesis of a sterically tailored ligand array (M)_2((C_5H_2-2-Si(CH_3)_3-4-C(CH_3)_3)S_2i(CH_3)_2]("M_2Bp") (M = Li, 16; K, 19) is described. Transmetallation of Li_2Bp with YCl_3(THF)_3 affords exclusively the C_2 symmetric product rac-[BpY(µ_2-Cl)_2Li(THF)_2], 20. A X-ray crystal structure of 20 has been determined; triclinic, P1, a= 13.110 (8), b = 17.163 (15), c = 20.623 (14) Å, α = 104.02 (7), β = 99.38 (5), γ = 100.24 (6)° , Z = 4, R = 0.056. Transmetallation of K_2Bp with YCl_3(THF)_3 affords the halide free complex rac-BpYCl, 23. The corresponding rac-BpLaCl, 28, is prepared in an anlogous manner. In all cases the achiral meso isomer is not obtained since only for the racemic isomers are the unfavorable steric interactions between the Si(CH3)_3 groups in the narrow portion of the [Cp-M'-Cp] wedge avoided. Alkylation of 20 or 23 with LiCH(Si(CH_3)_3)_2 affords rac-BpYCH(Si(CH_3)_3)_2, 26 in good yield. Alkylation of 28 with LiCH(Si(CH_3)_3)_2 affords rac-BpLaCH(Si(CH_3)_3)_2 29. Hydrogenation of 26 cleanly affords the bridging hydride species [BpY(µ_2-H)]_2, 27, as the homochiral (R,R) and (S,S) dimeric pairs. 26 is an efficient initiator for the polymerization of ethylene to high molecular weight linear polyethylene. 27 catalyzes the polymerization of propylene (25% v/v in methylcyclohexane) and neat samples of 1-butene, 1-pentene, 1-hexene to moderately high molecular weight polymers: polypropylene (M_n = 4,200, PDI 2.32, T_m 157 °C); poly-1-butene (M_n = 8,500, PDI 3.44, T_m 105 °C); poly-1-pentene (M_n = 20,000, PDI 1.99, T_m 73 °C); poly-1-hexene (M_n = 24,000, PDI 1.75, T_m < 25 °C). ^(13)C NMR spectra at the pentad analysis level indicates that the degree of isotacticity is 99% mmmm for all polymer samples. 27 is the first single component iso-specific α-olefin polymerization catalyst. The presumed origins of the high isospecificity are presented.

Published
1994
Full Text
View/download PDF

146. Duplex strand formation using alternating copolymers

Author

Nakade, Hiroshi, primary, IlkerCurrent address: Department of, M. Firat, additional, Jordan, Brian J., additional, Uzun, Oktay, additional, LaPointe, Nicholas L., additional, Coughlin, E. Bryan, additional, and Rotello, Vincent M., additional

Published
2005
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results