@article{teator_varner_knutson_sorensen_leibfarth_2020, title={100th Anniversary of Macromolecular Science Viewpoint: The Past, Present, and Future of Stereocontrolled Vinyl Polymerization}, volume={9}, ISSN={2161-1653 2161-1653}, url={http://dx.doi.org/10.1021/acsmacrolett.0c00664}, DOI={10.1021/acsmacrolett.0c00664}, abstractNote={The thermomechanical properties exhibited by synthetic macromolecules can be directly linked to their tacticity, or the relative stereochemistry of repeat units. The development of stereoselective coordination-insertion polymerization, for example, led to the discovery of isotactic polypropylene, now one of the most widely produced commodity plastics in the world. Widespread interest in controlling polymer tacticity has led to a variety of stereoselective polymerization methodologies; however, this area of polymer science has lagged behind when compared to the ability to control molecular weight, dispersity, and composition. Despite decades of advancements, many stereoregular vinyl polymers remain unknown, particularly those comprised of polar functionality or derived from renewable resources. This Viewpoint provides an overview of recent developments in stereocontrolled polymerization, with an emphasis on propagation mechanism, and highlights successes, limitations, and future challenges for continued innovation.}, number={11}, journal={ACS Macro Letters}, publisher={American Chemical Society (ACS)}, author={Teator, Aaron J. and Varner, Travis P. and Knutson, Phil C. and Sorensen, Cole C. and Leibfarth, Frank A.}, year={2020}, month={Oct}, pages={1638–1654} }
 @article{varner_teator_reddi_jacky_cramer_leibfarth_2020, title={Mechanistic Insight into the Stereoselective Cationic Polymerization of Vinyl Ethers}, volume={142}, ISSN={0002-7863 1520-5126}, url={http://dx.doi.org/10.1021/jacs.0c08254}, DOI={10.1021/jacs.0c08254}, abstractNote={The control of the tacticity of synthetic polymers enables the realization of emergent physical properties from readily available starting materials. While stereodefined polymers derived from nonpolar vinyl monomers can be efficiently prepared using early transition metal catalysts, general methods for the stereoselective polymerization of polar vinyl monomers remain underdeveloped. We recently demonstrated asymmetric ion pairing catalysis as an effective approach to achieve stereoselective cationic polymerization of vinyl ethers. Herein, we provide a deeper understanding of stereoselective ion-pairing polymerization through comprehensive experimental and computational studies. These findings demonstrate the importance of ligand deceleration effects for the identification of reaction conditions that enhance stereoselectivity, which was supported by computational studies that identified the solution-state catalyst structure. An evaluation of monomer substrates with systematic variations in steric parameters and functional group identities established key structure-reactivity relationships for stereoselective homo- and copolymerization. Expansion of the monomer scope to include enantioenriched vinyl ethers enabled the preparation of an isotactic poly(vinyl ether) with the highest stereoselectivity (95.1% ± 0.1 meso diads) reported to date, which occurred when monomer and catalyst stereochemistry were fully matched under a triple diastereocontrol model. The more complete understanding of stereoselective cationic polymerization reported herein offers a foundation for the design of improved catalytic systems and for the translation of isotactic poly(vinyl ether)s to applied areas.}, number={40}, journal={Journal of the American Chemical Society}, publisher={American Chemical Society (ACS)}, author={Varner, Travis P. and Teator, Aaron J. and Reddi, Yernaidu and Jacky, Paige E. and Cramer, Christopher J. and Leibfarth, Frank A.}, year={2020}, month={Sep}, pages={17175–17186} }
 @article{teator_varner_jacky_sheyko_leibfarth_2019, title={Polar Thermoplastics with Tunable Physical Properties Enabled by the Stereoselective Copolymerization of Vinyl Ethers}, volume={8}, ISSN={2161-1653 2161-1653}, url={http://dx.doi.org/10.1021/acsmacrolett.9b00802}, DOI={10.1021/acsmacrolett.9b00802}, abstractNote={A series of isotactic, semicrystalline vinyl ether copolymers (up to 94% meso diads) were synthesized using a chiral BINOL-based phosphoric acid in combination with a titanium Lewis acid. This stereoselective cationic polymerization enabled the systematic tuning of both glass transition (Tg) and melting temperature (Tm) in copolymers derived from alkyl vinyl ethers (i.e., ethyl, butyl, isobutyl). Additionally, a vinyl ether comonomer bearing an acyl-protected alcohol was utilized as a platform for postfunctionalization. Copolymers containing the masked alcohols were shown to undergo deprotection and subsequent coupling with a desired acid chloride. Collectively, these results highlight the diverse material properties and expanded chemical space accessible through stereoselective cationic polymerization mediated by a chiral anion.}, number={12}, journal={ACS Macro Letters}, publisher={American Chemical Society (ACS)}, author={Teator, Aaron J. and Varner, Travis P. and Jacky, Paige E. and Sheyko, Karolina A. and Leibfarth, Frank A.}, year={2019}, month={Nov}, pages={1559–1563} }
 @article{reis_varner_leibfarth_2019, title={The Influence of Residence Time Distribution on Continuous-Flow Polymerization}, volume={52}, ISSN={0024-9297 1520-5835}, url={http://dx.doi.org/10.1021/acs.macromol.9b00454}, DOI={10.1021/acs.macromol.9b00454}, abstractNote={Continuous-flow chemistry is emerging as an enabling technology for the synthesis of precise polymers. Recent advances in this rapidly growing field have hastened a need for a fundamental understanding of how fluid dynamics in tubular reactors influence polymerizations. Herein, we report a comprehensive study of how laminar flow influences polymer structure and composition. Tracer experiments coupled with in-line UV–Vis spectroscopy demonstrate how viscosity, tubing diameter, and reaction time affect the residence time distribution (RTD) of fluid in reactor geometries relevant for continuous-flow polymerizations. We found that the breadth of the RTD has strong, statistical correlations with reaction conversion, polymer molar mass, and dispersity for polymerizations conducted in continuous flow. These correlations were demonstrated to be general to a variety of different reaction conditions, monomers, and polymerization mechanisms. Additionally, these findings inspired the design of a droplet flow reactor that minimizes the RTD in continuous-flow polymerizations and enables the continuous production of well-defined polymers at a rate of 1.4 kg/day.}, number={9}, journal={Macromolecules}, publisher={American Chemical Society (ACS)}, author={Reis, Marcus H. and Varner, Travis P. and Leibfarth, Frank A.}, year={2019}, month={May}, pages={3551–3557} }