Polymeric Materials: Tailored Structure, Properties, and Function
The objective of our research group is to develop polymeric materials with enhanced physical properties and function. We specialize in polymer synthetic techniques, structural characterization (small-angle neutron, x-ray and light scattering), thermodynamics and self-assembly, and development of structure-property relationships.
Sustainable and biodegradable polymers derived from renewable resources
A major emphasis of our group is the development of sustainable sources for polymers to mitigate their environmental impact, as traditional petroleum sources for polymers are in finite supply and can lead to harmful land, water, and air pollution. Our overarching objective is to address key scientific challenges enabling the broad implementation of biobased, renewable resources to develop polymers with tunable physical properties that are competitive or enhanced relative to traditional petroleum-derived materials. Importantly, the structure-property-function relationships for these new materials are significantly different from those described in the vast body of literature for petroleum-derived polymers. The development of these relationships is necessary prior to a large-scale shift to biomass-sourced materials. We have explored a diverse range of polymers derived from biorenewable resources, including thermoplastics, elastomers, thermosets, and thermoplastic elastomers.
We are exploring polyacrylates derived from fatty acids, which contain long alkyl side-chains, as replacements for commercially dominant amorphous, rubbery polymers, such as polydienes, in targeted applications including thermoplastic elastomers and polymer blends. We discovered the number of carbon atoms on the alkyl side-chain has dramatic implications for the thermal and mechanical properties of the polymers (Wang et al. Macromolecules 2013), whereas, surprisingly, the thermodynamic interactions governing the self-assembly of a polymer blend or block copolymer containing long-chain polyacrylates were unaffected by the alkyl side-chain length (Wang et al. ACS Appl. Mat. Int. 2015). We explored the unanticipated development of close-packed spherical microstructures in bulk triblock copolymers under shear, attributed to the high dispersity of the block copolymer (Wang et al. Macromolecules 2016).
We investigated the properties of thiol-ene elastomers, relevant for coatings and adhesives, employing plant-sourced phenolic acids (Yang et al. Macromolecules 2015). The crosslink density and mechanical properties were highly dependent on the allylated phenolic acid functionality and network structure.
A multifunctional vegetable oil, acrylated epoxidized soybean oil, was investigated as a renewable additive to improve the toughness of the biodegradable thermoplastic polylactide (Mauck et al. Macromolecules 2016).
Glassy polymers (derived from plant-sourced phenolic acids) were developed as replacements for polystyrene, a dominant polymer used in industrial applications (Wang et al. Macromol. Chem. Phys. 2016).
Advanced materials for wind energy
We aim to develop advanced materials for wind energy, namely epoxy resins, with enhanced properties. We have three overarching goals: 1) improve the toughness and ductility of epoxy resins to promote tougher, longer life, and potentially lighter blade designs, 2) utilize sustainable, non-toxic feedstocks to replace bisphenol A in epoxy resins, and 3) design epoxy networks with degradable moieties, providing sustainable end-of-life options such as composting, to avoid disposal in landfills.
We are developing thermoset blends of an epoxy resin (high strength and modulus) and poly(dicyclopentadiene) (a ductile and tough thermoset) (Rohde et al. Polymer 2015).
We have probed epoxy resins containing epoxidized soybean oil, which contains degradable ester linkages (Yang et al. Green Mater. 2013).
Plant-sourced phenolic acids were investigated as replacements for bisphenol A, producing epoxy resins of desirable mechanical and thermal properties.
Structure and dynamics of block copolymer micelles
Our objective is to leverage both small-angle neutron scattering and nuclear magnetic resonance techniques to probe the impact of an encapsulated species (i.e. a model for a therapeutic drug) on the micelle structure and assembly. We investigated poly(ethylene oxide-b-e-caprolactone) diblock copolymer micelles, in which a model additive, tetrahydrofuran, was employed to probe the impact of a guest species on the micelle structure. Additionally, we utilized fluorescence spectroscopy to characterize the kinetics of guest exchange in the micelles (Xie et al. Soft Matter 2016).
pH-responsive, antifouling polymer brushes
Our group is designing pH-responsive, antifouling and self-cleaning surfaces. We investigated polyelectrolyte brush systems which exhibit hysteretic memory behavior, governed by the polymer dispersity, a previously unexplored brush property (Yadav et al. Soft Matter 2016).
Multicomponent and multiphase polymer blends
We are exploring the thermodynamics of multicomponent, multiphase blends of polyolefins and polydienes. We will address unaddressed questions regarding the impact of saturation on phase behavior.