Controlled Polymerizations of Polyimines 

Chemical reaction scheme showing the anionic polymerization of aziridines and azetidines

Polyethyleneimine (PEI) and related nitrogen-rich polymers have several important scientific, industrial, and commercial applications, including use in CO2 capture, non-viral gene transfection vectors, anti-microbial films, ion conductors, etc.   The direct route to PEI is the cationic ring-opening polymerization of aziridine, which produces hyperbranched PEI (bPEI).    Although bPEI is suitable for many applications, the linear form of PEI (lPEI) is prized when precise control over polymer structure and molecular weight is needed (e.g., in medical applications).

The Rupar group is developing synthetic strategies for synthesizing lPEI and linear forms of related polymers via the sulfonyl activation of aziridines and azetidines.   Long-term goals include the incorporation of these polymers into complex macromolecular structures and the use of these materials in biological applications.

Representative Publications:

Boron Containing Conjugated Systems
The absorption and emission spectra of a borafluorene.

The incorporation of inorganic elements into conjugated systems is an established technique used to alter the optoelectronics of these molecules.  The inclusion of three coordinate boron into conjugated frameworks is of special interest as the empty p-orbital on boron increases the electron affinity and the Lewis acidity of the molecule.  Given their unique properties, boron containing conjugated materials, both polymers and small molecules, have found applications as catalysts, electron transporting materials, emitters in OLEDs, and as sensors.

The Rupar group is studying the optical and electronic properties of boron containing conjugated molecules and polymers for use in organic electronics and as sensors.   Recent work has focused on a class of conjugate boron systems with unique optical properties, include molecules with record setting fluorescence Stokes Shifts and dual emissions.

Representative Publications: