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Ion-containing polymers: Our research team utilizes common organic reactions to develop novel polymeric architectures which contain ionic liquid (IL) units. Ionic liquids (ILs) have developed from novelty materials to commercially viable materials for the dissolution of cellulose and in various electroactive devices. Furthermore,  "designer" ionic liquids continue to be developed for specific applications. Our goal is to synthesis IL monomers that can be utilized in new ion-containing polymeric architectures. 

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Michael Addition Polymerization involves an IL-functionalized bisacetoacetate monomer and a multi-functional acrylate. In the presence of base, these materials will react to form covalently crosslinked, ion-containing polyester networks. To date, we have looked at imidazolium, 1,2,4- and 1,2,3-triazolium-functionalized IL monomers with various counteranions, at various acetoacetate:acrylate functional group ratios, creating flexibility in the amount of crosslink density. 

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For additional information on this project, see the following publications (* - denotes MSU undergraduate author)

1. Kim, S.*; Miller, K. M. “Synthesis and Thermal Analysis of Crosslinked Imidazolium-Containing Polyester Networks Prepared by Michael Addition Polymerization.” Polymer 2012, 53, 5666-5674.

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2. Whittington, C. P*, Daily, L. A.*; Miller, K. M. "Crosslinked Imidazolium-Containing Polyester Networks Containing a Pendant Imidazolium Group:  Swelling Studies and Thermal Properties." Polymer, 2014, 55, 3320-3329. 

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3. De La Hoz, A. T.*; Miller, K. M. "Covalently Crosslinked 1,2,4-Triazolium-containing Polyester Networks Prepared by Michael Addition Polymerization." Polymer 2015, 72, 1-9.

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4. Nguyen, A.*; Rhoades, T. C.*; Johnson, R. D.; Miller, K. M. "Influence of Anion and Crosslink Density on the Ionic Conductivity of 1,2,3-Triazolium-based Poly(ionic liquid) Polyester Networks." Macromol. Chem. Phys. 2017, 218, 1700337.​

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5. Tracy, C. A.*; Adler, A. M.*; Nguyen, A.*; Johnson, R. D.; Miller, K. M. "Covalently Crosslinked 1,2,3-Triazolium-Containing Polyester Networks:  Thermal, Mechanical and Conductive Properties." ACS Omega 2018, 3, 13442-13453. 3, 13442-13453.

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Thiol-ene photopolymerization: Thiol-ene chemistry has been heavily utilized in a variety of applications where a covalently crosslinked networks is needed. This 'click' reaction is very facile, occurring within minutes when exposed to UV irradiation when a photoinitiator is used. We have employed this approach to crosslink imidazolium-containing 'ene' monomers with commercially available, multi-functional thiols. The thiol:ene functional group ratio can be varied in an effort to control crosslink density and ionic conductivity. 

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For additional information on this project, see the following publications (* - denotes MSU undergraduate author)

Lindenmeyer, K. M.*; Miller, K. M. Thiol-yne Photoclick Polymerization as a Method for Preparing Imidazolium-Containing Ionene Networks. J. Polym. Sci. 2021, https://doi.org/10.1002/pol.20210629

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Bontrager, N. C.*; Radomski, S.***; Daymon, S. P.*; Johnson, R. D.; Miller, K. M. Influence of Counteranion and Humidity on the Thermal, Mechanical, and Conductive Properties of Covalently Crosslinked Ionenes. Polymer 2021, 222, 123641.

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Rhoades, T. C.*, Wistrom, J. C.*, Johnson, R. D., Miller, K. M. "Thermal, mechanical and conductive properties of imidazolium-containing thiol-ene poly(ionic liquid) networks." Polymer 2016, 100, 1-9. 

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Bratton, A. F.*; Kim, S.; Ellison, C. J.; Miller, K. M. "Thermomechanical and Conductive Properties of Thiol-ene Poly (ionic liquid) Networks Containing Backbone and Pendant Imidazolium Groups." Ind. Eng. Chem. Res. 2018, 57, 16526-16536.

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Sims, S. M.*; Bontrager, N. C.*; Whittaker, R. E.; Miller, K. M. "Correlating Structure with Ionic Conductivity in Bis(phosphonium)-containing Thiol-ene Networks." Polym. Int. 2019, 68, 1557-1565.

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Novel Ion-containing polymers and composites:

Our research team is interested in new syntheses of ion-containing polymers and composites, in particular those which contain ionenes. Recently, our group has developed a new ionene-PIL composite approach wherein a PIL network is polymerized around an ionene. This work continues in collaboration with Dr. Jason Bara's group at the University of Alabama.

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For more information, see: O'Harra, K. E.; Timmermann, G. M.*; Bara, J. E.; Miller, K. M. Designing Ionic Liquid-Derived Polymer Composites from Poly(Ionic Liquid)-Ionene Semi-interpenetrating Networks. ACS Polym. Mater. 2021, ASAP article.

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Sustainability in Polymer Science: We have several projects that highlight the desire to pursue improvements in sustainability and/or recycling in polymer science. (updates in progress!!)

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Multi-block copolymers for recycling mixed plastic waste: PET and PE are two the largest volume commercial plastics. Individually they can be recycled; however, when mixed (i.e. PET-PE composites), recycling is extremely difficult. In collaboration with Dr. Christopher Ellison (University of Minnesota), we have developed PET-PE multi-block copolymers which act as effective compatibilizers for recycling PET-PE mixtures.

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For more information, see: Nomura, K.; Peng, X.; Kim, H.; Jin, K.; Bratton, A. F.*, Bond, C. R.; Broman, A. E.; Miller, K. M.; Ellison, C. J. "Multiblock Copolymers for Recycling Polyethylene-Poly(ethylene terephthalate) Mixed Waste." ACS Appl. Mater. Interfaces 2020, 12, 9726-9735. 

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Converting cellulose into ion-conducting materials: Cellulose represents one of the most abundant, sustainable resources on the planet. In our laboratories we are functionalizing cellulose with ionic liquid groups in an effort to create novel ion-conducting biomacromolecules. This work continues in collaboration with Dr. David Salas-de la Cruz and his team at Rutgers University, Camden campus.

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For more information, see: Miller, R. J.*; Smith, V. M.*; Love, S. A.; Byron, S. M.*; Salas-de la Cruz, D.; Miller, K. M. Synthesis and Evaluation of Cellulose-based, 1,2,3-Triazolium-functionalized Polymerized Ionic Liquids: Thermal Transitions, Ionic Conductivities, and Morphological Properties. ACS Appl. Polym. Mater. 2021, 3, 1097-1106

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Utilization of Industrial Hemp for the Manufacturing of Wood-like Construction Materials: In 2019, HempWood, a company operated in Murray, KY, came to MSU for expertise in the development of a bio-based, sustainable adhesive for their product lines. Industrial (non-THC) hemp is a sustainable raw material which sequesters carbon dioxide at a significantly faster rate than trees (oak, pine, etc.) of which traditional wood flooring is made from. Our team has successfully worked with HempWood to develop a soy-based, non-VOC adhesive for their main hemp wood product line. Our current efforts are focused on working with HempWood to further improve the water resistance of the current product line and to begin investigating the incorporation of hemp into other building construction materials. 

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Research Sponsors: Dr. Miller and his research team are grateful for support (past and present) from all of the following funding agencies.

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Research Equipment:

 

Our lab is equipped with two fume hoods and 600 square feet of research space.  We currently have three high vacuum pumps, two Schlenk lines, a Metrohm potentiostat with humidity-controlled oven for dielectric studies, and adequate bench and storage space to support all synthetic efforts of our research group. Additionally, Dr. Miller is the coordinator for the Polymer and Materials Science Laboratory. Students in our group have access to all of this state-of-the-art equipment!

 

Polymer and Materials Characterization Laboratory (PMCL):  The Polymer and Materials Characterization Laboratory (PMCL) in a dedicated laboratory designed to support research and educational efforts in polymer and materials science.  Included in the PMCL are the DSC, TGA, GPC, Antor Parr Densitometer, two variable temperature viscometers, a Waters GPC unit, a Dynamic Mechanical Analyzer (NSF-MRI) and a rheometer (with dielectric and UV curing accessories) (NSF-MRI).

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If you have interest in working with the PMCL on your project, please contact Dr. Miller at (270) 809-3543 or by e-mail:  kmiller38@murraystate.edu.  We enjoy working with external partners on their synthetic and analytical projects!

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