The Long Research Group
Macromolecular Chemistry and Catalyst Design
RESEARCH
Information About Specific Projects
Olefin Polymerization Catalysis
Polyolefins are commodity plastics derived from inexpensive and readily available olefinic feedstocks, such as ethylene and propylene. They exhibit a range of thermal and mechanical properties, and are perfect candidates for a plethora of applications. Since their discovery, researchers in both industry and academia have worked diligently to understand and optimize the synthesis of these materials. Though much has been learned, a few challenges still remain such as the limited thermal stability of many catalysts, and the development of advanced catalysts that avoid the outdated paradigm of “one catalyst, one polymer.” To address these issues, the Long Research Group aims to: 1) develop thermally robust late transition metal catalysts and 2) utilize redox-active ligands that are able to influence the catalytic behavior of olefin polymerization catalysts.
More specifically, the Long Research Group has shown that bulky ligands can be used to enhance the thermal stability of various late transition metal-based catalysts. Some of these catalysts show temporal stability at temperatures as high as 90-100 °C, while some have even proven to polymerize ethylene in a living fashion at temperatures as high as 75 °C. In regards to redox-active catalysts, the Long Group has reported a series of Ni-based catalysts that are able to predictably control polyolefin microstructure as a function of redox-state. This work was then extended to include olefin copolymerizations, and has even been used to access multiple polyethylene grades using a single catalyst species. Lastly, we demonstrated that these redox-switching capabilities may be accessed using photoredox mediated chemistry, rather than via the sequential addition of standard chemical oxidants and reductants.
SELECTED PUBLICATIONS:
Mitchell, N. E.; Long, B. K. “Recent Advances in Thermally Robust, Late Transition Metal Catalyzed Olefin Polymerization” Polymer International, 2019, 68,14-26. DOI: 10.1002/pi.5694
Kaiser, J. M.; Long, B. K. “Recent developments in redox-active olefin polymerization catalysts” Coordination Chemistry Reviews, 2018, 372, 141-152. DOI: 10.1016/j.ccr.2018.06.007
Brown, L. A.; Anderson Jr., W. C., Mitchell, N. A.; Gmernicki, K. R.; Long, B. K. “High Temperature, Living Polymerization of Ethylene by a Sterically-Demanding Nickel(II) a-Diimine Catalyst” Polymers, 2018, 10, 41. DOI: 10.3390/polym10010041
Kaiser, J. M.; Anderson Jr., W. C., Long, B. K. “Photochemical regulation of a redox-active olefin polymerization catalyst: controlling polyethylene microstructure with visible light” Polymer Chemistry, 2018, 9, 1567-1570. DOI: 10.1039/C7PY01836C
Mitchell, N. A.; Anderson Jr., W. C., Long, B. K. “Mitigating Chain-transfer and Enhancing the Thermal Stability of Co-based Olefin Polymerization Catalysts through Sterically Demanding Ligands” J. Poly. Sci. A, 2017, 55, 3990. DOI: 10.1002/pola.28783
Anderson Jr., W. C,; Rhinehart, J.L.; Tennyson, A. G.; Long, B. K. “Redox-Active Ligands: An Advanced Tool to Modulate Polyethylene Microstructure” J. Am. Chem. Soc. 2016, 138, 774. DOI: 10.1021/jacs.5b12322
Gas Separation Membranes
The industrial scale separation and purification of chemical mixtures accounts for approximately 10-15% of the world’s energy consumption. Because of this, methods by which these chemical separations can be accomplished in a more energy-efficient and cost-effective manner are highly desired. One particular technology that has shown tremendous promise is the use of polymeric gas separation membranes. Polymeric membranes have been targeted for a variety of applications including the separation of light-hydrocarbons, natural gas purification, and even the separation of harmful greenhouse gases such as carbon dioxide (CO2). However, despite their broad interest, the industrial-scale implementation of gas separation membranes has remained relatively limited due to a variety of scientific and practical limitations such as an overall lack of understanding of how molecular-level hierarchical controls may be harnessed to promote membrane performance.
To address this grand challenge, our research focuses on the development of tailored polymeric membranes that are accessed using multiple synthetic methodologies and polymerization techniques. As an example, we have recently shown that vinyl-added polynorbornenes (VA-PNBs) bearing polar functionalities, such as alkoxysilanes, can be readily accessed in high yields and high molecular weights. VA-PNBs typically have remarkable mechanical properties and have high glass-transition temperatures (Tg), usually near their decomposition temperature (Td). These alkoxysilane-substituted materials have shown tremendous promise for the separation of carbon dioxide (CO2) from non-harmful gases such as N2. CO2 accounts for approximately 82% of all U.S greenhouse gas emissions and has been linked to climate change and negative effects on human health and well-being.
SELECTED PUBLICATIONS:
Higgins, M. A.; Maroon, C. R.; Townsend, J.; Wang, X.; Vogiatzis, K. D.; Long, B. K. “Evaluating the impact of functional groups on membrane-mediated CO2/N2 gas separations using a common polymer backbone” J. Poly. Sci. 2020, just accepted. DOI: 10.1002/pol.20200150
Maroon, C. R.; Townsend, J.; Higgins, M. A.; Harrigan, D. J.; Sundell, B. J.; Lawrence, J. A.; O'Brien, J. T.; O'Neal, D.; Vogiatzis, K. D.; Long, B. K.“Addition-type Alkoxysilyl-Substituted Polynorbornenes for Post-Combustion Carbon Dioxide Separations” J. Membrane Sci. 2020, 595, 117532. DOI: 10.1016/j.memsci.2019.117532
Maroon, C. R.; Townsend, J.; Gmernicki, K. R.; Harrigan, D. J.; Sundell, B. J.; Lawrence, J. A.; Mahurin, S. M.; Vogiatzis, K. D.; Long, B. K. “Elimination of CO2/N2 Langmuir Sorption and Promotion of “N2‑Phobicity” within High‑TgGlassy Membranes” Macromolecules 2019, 52, 1589-1600. DOI: 10.1021/acs.macromol.8b02497
Belov, N.; Nikiforov, R.; Starannikova, L.; Gmernicki, K. R.; Maroon, C. R.; Long, B. K.; Shantarovich, V.; Yampolskii, Y. “A Detailed Investigation into the Gas Permeation Properties of Addition-type Poly(5-triethoxysilyl-2-norbornene)” Eur. Poly. J. 2017, 93, 602. DOI: 10.1016/j.eurpolymj.2017.06.030
Feng, H.; Hong, T.; Mahurin, S. M.; Vogiatzis, K. D.; Gmernicki, K. R.; Long, B. K.; Mays, J. W.; Sokolov, A. P.; Kang, N. G.; Saito, T. “Gas separation mechanism of CO2 selective amidoxime-poly(1-trimethylsilyl-1-propyne) membranes” Polym. Chem., 2017, 8, 3341-3350. DOI: 10.1039/C7PY00056A
Gmernicki, K. R.; Hong, E.; Maroon, C. R.; Mahurin, S. M.; Sokolov, A. P.; Saito, T.; Long, B. K. “Accessing Siloxane Functionalized Polynorbornenes via Vinyl-Addition Polymerization for CO2 Separation Membranes” ACS Macro Lett., 2016, 5, 879. DOI: 10.1021/acsmacrolett.6b00435
Hong, T.; Niu, Z.; Hu, X.; Gmernicki, K.; Cheng, S.; Fan, F.; Johnson, J. C.; Hong, E.; Mahurin, S.; Jiang, D.; Long, B.; Mays, J.; Sokolov, A.; Saito, T. “Effect of Cross-Link Density on Carbon Dioxide Separation in PDMS Norbornene Membranes” ChemSusChem, 2015. 8, 3595. DOI: 10.1002/cssc.201500903
Copolymers for Protein Extraction
SELECTED PUBLICATIONS:
Workman, C.E.; Bag, P.; Cawthon, B.; Ali, F. H.; Brady, N. G.; Bruce, B. D.; Long, B. K. “Alternatives to Styrene- and Diisobutylene-based Copolymers for Membrane Protein Solubilization via Nanodisc Formation” Angew. Chem. Int. Ed. 2023, accepted.
Workman, C.E.; Cawthon, B.; Brady, N.G.; Bruce, B.D.; Long, B. K. “Effects of Esterified Styrene-Maleic Acid Copolymer Degradation on Integral Membrane Protein Extraction” Biomacromolecules 2022, 23, 4749. DOI: 10.1021/acs.biomac.2c00928
Brady, N.G.*; Workman, C.E.*; Cawthon, B.; Bruce, B.D.; Long, B. K. “Protein Extraction Efficiency and Selectivity of Esterified Styrene–Maleic Acid Copolymers in Thylakoid Membranes” Biomacromolecules 2021, 22, 2544. DOI: 10.1021/acs.biomac.1c00274
Advanced Materials
Polymeric materials provide a unique avenue by which molecular design may be leveraged at the monomeric, polymeric, and bulk scales to obtain desirable properties and/or performance in demanding applications. These materials have become an intricate part of the world around us, and as such, require an intimate entanglement of both chemistry and engineering concepts. Fundamental research projects in the Long Research Group have looked at the synthesis of alternating and non-alternating copolymers for a variety of applications, as well as the design and mechanochemical activation of functionalized polynorbornenes synthesized via vinyl-addition polymerization. Lastly, we have explored the incorporation of DNA-inspired units into organic polymers, which is an active collaboration with Prof. Michael Kilbey and his research group. Therein, our primary interest has been to find efficient methods by which purine-derived sub-units may be incorporated into polymeric materials. By incorporating these purine units into a polymeric backbone, we have demonstrated the ability to tune their thermal, optoelectronic, and even H-bonding characteristics.
SELECTED PUBLICATIONS:
Lee, D. C.; Kensy, V. K.; Maroon, C. R.; Long, B. K.; Boydston, A.J. “The intrinsic mechanochemical reactivity of vinyl-addition polynorbornene” Angew. Chem. Int. Ed. 2019, 58, 5639-5642. DOI: 10.1002/anie.201900467
Collier, G. S.; Brown, L. A.; Boone, E. S.; Kaushal, M.; Walter, M. G.; Long, B. K.; Kilbey, S. M. ” Synthesis of Donor-Acceptor Purine-Based Chromophores and an Investigation of Thermal, Photophysical, and Electrochemical Properties ” J. Mater. Chem. C, 2017, 5, 6891. DOI: 10.1039/C7TC01835E
Collier, G. S.; Brown, L. A.; Boone, E. S.; Long, B. K.; Kilbey, S. M. “Synthesis of Main Chain Purine-Based Copolymers and Effects of Monomer Design on Thermal and Optical Properties” ACS Macro Lett., 2016, 5, 682. DOI: 10.1021/acsmacrolett.6b00275
Gmernicki, K. R.; Cameron, M.; Long, B. K. “Fundamental Investigations into the Free-radical Copolymerization of N-phenylmaleimide and Norbornene” J. Poly. Sci. A, 2016,54, 985. DOI: 10.1002/pola.27934
