東華大學圖書館 |

Language: English

Help

回圖書館首頁

手機版館藏查詢

Back

Switch To: Labeled | MARC Mode | ISBD

Mechanistic investigations of titani...

Mahanthappa, Mahesh Kalyana.

Linked to FindBook

Google Book

Amazon

博客來

Mechanistic investigations of titanium-mediated syndiospecific styrene polymerizations.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Mechanistic investigations of titanium-mediated syndiospecific styrene polymerizations./
Author:	Mahanthappa, Mahesh Kalyana.
Description:	200 p.
Notes:	Source: Dissertation Abstracts International, Volume: 64-05, Section: B, page: 2193.
Contained By:	Dissertation Abstracts International64-05B.
Subject:	Chemistry, Organic. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3090641
ISBN:	0496383639

Mechanistic investigations of titanium-mediated syndiospecific styrene polymerizations.
Mahanthappa, Mahesh Kalyana.

Mechanistic investigations of titanium-mediated syndiospecific styrene polymerizations. - 200 p.

Source: Dissertation Abstracts International, Volume: 64-05, Section: B, page: 2193.

Thesis (Ph.D.)--Stanford University, 2003.

Catalysts derived from half-metallocene complexes such as CpTiCl 3 activated with methylaluminoxane polymerize styrene to syndiotactic polystyrene (sPS), a semi-crystalline, high temperature engineering thermoplastic exhibiting a high melting temperature Tm = 270°C and a high glass transition temperature Tg =100°C. The low level of toughness exhibited by this polymeric material and its brittleness at room temperature have prevented widespread use of sPS. Attempts to improve the mechanical properties of sPS by copolymerization with ethylene have been unsuccessful to date and yield mixtures of polyethylene, syndiotactic polystyrene, and random ethylene-styrene copolymers. This observation has led to hypotheses that different oxidation states are responsible for ethylene polymerization and styrene homopolymerization. In order to address the role of oxidation state on catalytic activity, syndiospecific styrene polymerizations were conducted using catalysts derived from the monomeric, well-defined Ti(IV) complex Cp*Ti(CH 2Ph)3 and the Ti(III) complex Cp*Ti(C3H5 )2. While catalysts derived from the Ti(IV) precursors are shown to be inactive for sPS production in the absence of light, catalysts derived from Ti(III) precursors are highly active catalysts for sPS synthesis. Propylene/styrene copolymerization studies demonstrate that catalysts derived from Ti(III) precursors exhibit high chemoselectivity for the homopolymerization of styrene, while catalysts derived from Ti(IV) complexes are competent for propylene/styrene co-oligomerization.

ISBN: 0496383639Subjects--Topical Terms:

516206
Chemistry, Organic.

Mechanistic investigations of titanium-mediated syndiospecific styrene polymerizations.
LDR:03717nmm 2200301 4500 001 1843781
005 20051017073359.5
008 130614s2003 eng d
020 $a 0496383639
035 $a (UnM)AAI3090641
035 $a AAI3090641
040 $a UnM $c UnM
100 1 $a Mahanthappa, Mahesh Kalyana. $3 1931999
245 1 0 $a Mechanistic investigations of titanium-mediated syndiospecific styrene polymerizations.
300 $a 200 p.
500 $a Source: Dissertation Abstracts International, Volume: 64-05, Section: B, page: 2193.
500 $a Adviser: Robert M. Waymouth.
502 $a Thesis (Ph.D.)--Stanford University, 2003.
520 $a Catalysts derived from half-metallocene complexes such as CpTiCl 3 activated with methylaluminoxane polymerize styrene to syndiotactic polystyrene (sPS), a semi-crystalline, high temperature engineering thermoplastic exhibiting a high melting temperature Tm = 270°C and a high glass transition temperature Tg =100°C. The low level of toughness exhibited by this polymeric material and its brittleness at room temperature have prevented widespread use of sPS. Attempts to improve the mechanical properties of sPS by copolymerization with ethylene have been unsuccessful to date and yield mixtures of polyethylene, syndiotactic polystyrene, and random ethylene-styrene copolymers. This observation has led to hypotheses that different oxidation states are responsible for ethylene polymerization and styrene homopolymerization. In order to address the role of oxidation state on catalytic activity, syndiospecific styrene polymerizations were conducted using catalysts derived from the monomeric, well-defined Ti(IV) complex Cp*Ti(CH 2Ph)3 and the Ti(III) complex Cp*Ti(C3H5 )2. While catalysts derived from the Ti(IV) precursors are shown to be inactive for sPS production in the absence of light, catalysts derived from Ti(III) precursors are highly active catalysts for sPS synthesis. Propylene/styrene copolymerization studies demonstrate that catalysts derived from Ti(III) precursors exhibit high chemoselectivity for the homopolymerization of styrene, while catalysts derived from Ti(IV) complexes are competent for propylene/styrene co-oligomerization.
520 $a Studies of the coordination chemistry of titanium complexes containing ligands derived from N,N-dialkylhydroxylamines and stable nitroxide radicals are presented with an emphasis on their abilities to serve as pre-catalysts for olefin polymerization. Structural characterization of (eta2-TEMPO)TiCl 3, [eta2-(CH3CH2)2NO] 2Ti(CH2Ph)2, and Cp'TiCl 2(eta1-TEMPO) (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl; Cp' = Cp and Cp*) shows that the binding mode of hydroxylaminato ligands to titanium depends sensitively on the steric requirements of the ligand as well as the ancillary ligation at titanium. The alkylation chemistry of these complexes is studied along with their abilities to serve as pre-catalysts for alpha-olefin homopolymerizations and copolymerizations. Catalysts derived from Cp*TiMe2(TEMPO) efficiently copolymerize ethylene and 1-hexene to yield copolymers with high 1-hexene contents. Comparisons of structural and electronic features and the ethylene/1-hexene copolymerization behavior of Cp*TiMe2(TEMPO) and Cp*Ti(CH2Ph)3 with the constrained geometry catalyst [MeSi2(eta5-Me 4Cp)(eta1-N-tBu)]TiMe2 provide insights into factors governing comonomer incorporation by mono-Cp titanium complexes.
590 $a School code: 0212.
650 4 $a Chemistry, Organic. $3 516206
650 4 $a Chemistry, Inorganic. $3 517253
650 4 $a Chemistry, Polymer. $3 1018428
690 $a 0490
690 $a 0488
690 $a 0495
710 2 0 $a Stanford University. $3 754827
773 0 $t Dissertation Abstracts International $g 64-05B.
790 1 0 $a Waymouth, Robert M., $e advisor
790 $a 0212
791 $a Ph.D.
792 $a 2003
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3090641