Seminar
Tuesday, November 14, 2017 - 12:00am
Graduate student Darian Waugh will present
Yttrium Bis(phenolate) Catalyzed Polymerization
on November 14, 2017 at 4:10 PM in Neville Hall, Room 3.
Abstract:
Polymers are typically formed through three types of polymerization reactions; free-radical, ionic, and coordination. Coordination polymerization is an extremely useful means of polymer preparation due to its increase in control of stereoregularity, tacticity, during the formation period. This polymerization reaction was first discovered by Zeigler and Natta, and showed that higher stereoregularity and better control of polymer linearity could be obtained by using transition metal catalysts.1 It has been shown that these catalysts work by binding to the unit of interest, performing an insertion reaction, hereby extending the chain hereby forming a longer polymer.
Rare-earth metal polymerization using Yttrium complexes has been shown to form tactic and high molecular weight polymers. The work to be discussed will focus on the use and application of Yttrium Bis(phenolate) complexes as coordination catalysts for use in polymerization reactions. Yttrium, when coordinated to bis(phenolate) either ligands, has been shown to perform stereoselective polymerization, yielding stereoregular polymers while maintaining a narrow molecular weight distribution. Using Yttrium Bis(phenolate), poly(2-vinylpyridine) is prepared showing both high molecular weight and isotactic characteristics.1,2 Copolymerization and homopolymerization of 1,3-butadiene and isoprene were achieved by use of the Yttrium Bis(phenolate) catalyst.3 Yttrium Bis(phenolate) catalysts have also been used in an isoselective-ring opening polymerization of racemic lactide.4 These catalysts were synthesized with different steric modifications and the stereo-control mechanism of polymerization was explored by use of both kinetic and computational techniques, demonstrating how Yttrium Bis(phenolate) either complexes can be used in formation of polymers that have high molecular weights while maintaining stereoregularity.
References:
Xu, T.; Yang, G.; lu, X. ACS Catal., 2016, 6, 4907-4913 Kronast, A.; Reiter, P.; Altenbuchner, P.; Vagin, S.; Rieger, B. Macromolecules, 2016, 49, 6260-6267 Hong, K.; Liang, Z.; Ni, X.; Shen, Z. RSC Adv., 2016, 6, 33828-33833 Xu, T.; Yang, C.; Liu, C.; Lu, X. Macromolecules, 2017, 50, 515-522