Polymer tacticity has a profound influence on macroscopic material properties, including the thermal, mechanical, and optical behavior of a material. Despite advancements in coordination-insertion polymerization methods used for the synthesis of stereoregular poly(α-olefin)s, polar isotactic polymers have remained a challenging synthetic target. This presentation will discuss our lab’s two-pronged approach to synthesize a unique class of polar, semi-crystalline thermoplastics through the stereoselective polymerization of vinyl ether monomers.<br/><br/>Inspired by recent progress in the field of small-molecule asymmetric ion pairing catalysis, we first explored interfacing chiral hydrogen bond donors in the cationic polymerization of vinyl ethers. The chiral complex generated from a triflate-bound squaramide biases the stereochemistry of monomer addition, giving a range of isotactic poly(vinyl ether)s. A complementary effort within our group discovered 1,1′-Bi-2-naphthol (BINOL)-derived Brønsted acids as a tunable chiral scaffold for Lewis acid-mediated stereoselective polymerization. In this lecture, I will present comprehensive structure–reactivity and kinetic studies enabling the elucidation of key design principles. The derivation of quantitative thermodynamic parameters will be discussed in relation to the enthalpic and entropic contributions relevant to stereoselective monomer addition. Furthermore, I will discuss how our fundamental understanding of stereoselective vinyl ether polymerization has enabled the realization of semi-crystalline thermoplastics derived from bio-renewable monomer building blocks with attractive thermomechanical and adhesion properties.

Stereocontrolled cationic polymerization of vinyl ethers

2019 Fall National Meeting

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