Regioselective, stereoselective, and living polymerization of divinyl pyridine monomers using rare earth catalysts?

Polymer Chemistry Pub Date: 2020-02-06 DOI: 10.1039/C9PY01852B

Abstract

The first regioselective, stereoselective, and living polymerization of divinyl pyridine monomers, mediated by simple rare earth catalysts, is reported. The polymerization by Ln(CH2SiMe3)3(L)2 (Ln = Sc, Y, Lu, Dy; L = THF, Py) is perfectly regioselective for a 2,5-divinylpyridine (DVP) monomer, and the process only concerned the double bond at the 2-position of DVP and the C[double bond, length as m-dash]C bond at the 5-position selectively remained unreacted. In contrast, the polymerization of DVP by La(CH2SiMe3)3(THF)2 is not regioselective, producing a cross-linking network. The polymerization by Lu(CH2SiMe3)3(Py)2/B(C6F5)3 is most stereoselective, yielding perfect isotactic PDVP with mmmm >99%. The isoselectivity (mm) of the polymers could be controlled in a range of 31% to 99% by adjusting the amount of THF added. The DVP polymerization is controlled by Lu[CH(C5H4N)CH2CH2SiMe3]3 (formed via in situ mixing of Lu(CH2SiMe3)3(THF)2 and 2-vinylpyridine), with the molecular weight (Mn) matching the theoretical value of monomer conversion and a narrow dispersity. The stereoblock polymerization of DVP with 2-vinylpyridine was achieved by adding the monomer sequentially. The post-functionalization of stereoblock polymers containing vinyl groups has been achieved by the thiol–ene “click” reaction in which all the C[double bond, length as m-dash]C double bonds are quantitatively converted to thioether bonds.

Graphical abstract: Regioselective, stereoselective, and living polymerization of divinyl pyridine monomers using rare earth catalysts
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