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4720522 
Journal Article 
Borane Chain Transfer Reaction in Olefin Polymerization Using Trialkylboranes as Chain Transfer Agents 
Lin, W; Niu, Hui; Chung, TCM; Dong, JinY 
2010 
Yes 
Journal of Polymer Science. Part A, Polymer Chemistry
ISSN: 0887-624X
EISSN: 1099-0518 
48 
16 
3534-3541 
WOS:000280567400005 
This article discusses a new borane chain transfer reaction in olefin polymerization that uses trialkylboranes as a chain transfer agent and thus can be realized in conventional single site polymerization processes under mild conditions. Commercially available triethylborane (TEB) and synthesized methyl-B-9-borabicyclononane (Me-B-9-BBN) were engaged in metallocene/MAO [depleted of trimethylaluminum (TMA)]-catalyzed ethylene (Cp(2)ZrCl(2) and rac-Me(2)Si(2-Me-4-Ph)(2)ZrCl(2) as a catalyst) and styrene (Cp*Ti(OMe)(3) as catalyst) polymerizations. The two trialkylboranes were found-in most cases-able to initiate an effective chain transfer reaction, which resulted in hydroxyl (OH)-terminated PE and s-PS polymers after an oxidative workup process, suggesting the formation of the B-polymer bond at the polymer chain end. However, chain transfer efficiencies were influenced substantially by the steric hindrances of both the substituent on the trialkylborane and that on the catalyst ligand. TEB was more effective than TMA in ethylene polymerization with Cp(2)ZrCl(2)/MAO, whereas it became less effective when the catalyst changed to rac-Me(2)Si(2-Me-4-Ph)(2)ZrCl(2). Both TEB and Me-B-9-BBN caused an efficient chain transfer in the Cp(2)ZrCl(2)/MAO-catalyzed ethylene polymerization; nevertheless, Me-B-9-BBN failed in vain with rac-Me(2)Si(2-Me-4-Ph)(2)ZrCl(2)/MAO. In the case of styrene polymerization with Cp*Ti(OMe)(3)/MAO, thanks to the large steric openness of the catalyst, TEB exhibited a high efficiency of chain transfer. Overall, trialkylboranes as chain transfer agents perform as well as B H-bearing borane derivatives, and are additionally advantaged by a much milder reaction condition, which further boosts their applicability in the preparation of borane-terminated polyolefins. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3534-3541, 2010 
functionalization of polymers; polyolefins; Ziegler-Natta polymerization