RESEARCH INTERESTS

Our research endeavors focus on the properties of nanoparticles (NPs), such as carbon-nanotubes and graphene, and conjugated polymers (CPs) that are well-suited for implementation in thermoelectric and optoelectronic devices. Specifically, our goals are (1) to study the impact of solvent properties on polymer assembly in the condensed phase, (2) to correlate the characteristics of CPs and NP/CP mixtures in solution to those of thin films and composites cast from the same solutions, and (3) to find novel routes to improving the morphology of CP thin films and NP/CP bulk-heterojunction composites. These studies will improve our understanding of phase separation, self-organization, and assembly in polymer-based nanomaterials and, from a much broader perspective, our work seeks to contribute to the ongoing research and development of emerging solar energy technologies.

 

The morphology of polymer-nanoparticle bulk-heterojunctions (BHJs) is well-known to impact their performance in electronic devices such as solar cells and field-effect transistors. Solution deposition under fast drying conditions e.g., spin coating, promotes polymer crystallization, but it can also induce unfavorable phase separation of the polymer-nanoparticle BHJ composite. The nature of the metastable polymer structures formed in solution are significant in determining the morphology of the photoactive materials after film casting. Systematic and detailed studies of polymer aggregation and organization in solutions are still relatively scarce and it is not yet clear which solvent systems are most suitable for nanofiber formation. To that end, we are currently using spectroscopic methodologies to investigate the impact of binary solvent systems on polymer aggregation and to characterize the resulting intermolecular interactions between the polymer aggregates and quantum dot nanoparticles.

Polymer/carbon nanotube and polymer/graphene systems have received considerable interest for their potentials applications as thermoelectric and photovoltaic materials. We are continuing to pursue synthetic methodologies that enhance the polymer/nanoparticle interactions, thereby improving the response and efficiency of the composites.

Associate Professor, Department of Chemistry and Biochemistry

Dr. David Boucher

SOLUTION-DIRECTED ASSEMBLY OF CONJUGATED POLYMERS

SOLUBILITY PARAMETER THEORY AND APPLICATIONS

Solubility parameter methods have proven very useful in an array of theoretical and practical applications. From an applications standpoint, solubility parameters are a practical and convenient way to evaluate polymer solubility in organic solvents, as well as the miscibility of semiconductor polymer-polymer and polymer-nanoparticle blends. With respect to more fundamental sciences, correlations between solubility parameter methods and well-known thermodynamic and molecular theories have contributed to our understanding of significant physicochemical system properties, solvent-solute affinities, equilibria, and the development of quantitative structure-property relationships and phase separation behavior in polymer-based materials. The determination of solubility behavior and solubility parameters represents a challenging mathematical problem of locating the central tendency of solvent affinity based on a limited set of data taken from experimental observations. Existing qualitative methodologies tend to generate varying and unreliable results, as well as a loss of important information regarding the nature of the intermolecular interactions between the solvent and solute. To overcome these issues our research group uses complementary experimental and computational techniques to develop new quantitative methods that make use of accurate solubility data to construct the compatibility space and generate the solubility parameters of polymers. In turn we use our results to (1) reveal information about the dominant intermolecular forces that govern the polymer solubility and (2) assess the stability of polymer solutions and polymer/nanoparticle blends.