Isotactic poly(1-butene) is a commodity thermoplastic material that has found important commercial use in a variety of applications. However, complex crystallization kinetics associated with this material can give rise to at least three different crystalline polymorphs upon cooling from the melt, that can further contribute to aging effects through the conversion of one crystalline modification into a more thermodynamically favored one over time. We have previously demonstrated successful stereoengineering of a polyolefin stereochemical microstructure by exerting external control over a two-state living coordination polymerization that involves interconversion between an active configurationally-stable chiral propagating species and a configurationally-unstable dormant state through rapid and reversible methyl group exchange that proceeds at a rate far greater than propagation. By controlling the relative populations of the active and dormant species as a function of time, the frequency of stereoerror incorporation can be established in programmed fashion.1-3 In this way, a single catalyst system is capable of providing a broad spectrum of different targeted grades of a polyolefin under nearly identical conditions, including unique stereoblock and stereogradient microstructures. This talk will present the results of a similar investigation of the ability to stereoengineer the physical properties of poly(1-butene) through application of stereomodulated two-state living coordination polymerization of 1-butene.(1) Zhang, Y.; Keaton, R. J.; Sita, L. R. J. Am. Chem. Soc. 2003  , 125, 9062.(2) Harney, M. B.; Zhang, Y.; Sita, L. R. Angew. Chem., Int. Ed. 2006  , 45, 2400.(3) Crawford, K. E.; Sita, L. R. J. Am. Chem. Soc. 2013  , 135, 8778.Figure 1.  13C NMR (150 MHz, 1,1,2,2-C2Cl4D2, 110 oC) Methyl region of poly(1-butene) materials with pentad stereosequence assignments as a function of decreasing % activation.

Stereoengineering of poly(1-butene) microstructure via stereomodulated two-state living coordination polymerization of 1-butene

247th National Meeting (2014)

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