Conjugated Polyelectrolytes: Properties and Applications

We study the properties and applications of a class of conjugated polymers called conjugated polyelectrolytes (CPEs).  These polymers are substituted with ionic (charged) groups such as sulfonate (-SO3), carboxylate (-COO) and ammonium (-NR3+), and the strong interactions between the charged groups and water molecules makes the polymers water soluble.  CPEs have a number of remarkable properties, which present interesting systems for basic science investigations, as well as for developing materials and devices for useful applications such as fluorescence sensors, biosensors and dye-sensitized solar cells.  Group members apply synthetic organic and polymer chemistry to prepare new and known conjugated polyelectrolytes and then we utilize them in a studies including fluorescence spectroscopy,  applications in biology, and fabrication and testing of solar cells.

General structures of conjugated polyelectrolytes

Conjuguated Polyelectrolyte Fluorescence Sensors

The fluorescence of conjugated polyelectrolytes (CPEs) is quenched with very high efficiency by small molecule quenchers with opposite charges. This effect has been referred to as amplified quenching or superquenching. We study the profound correlation between the fluorescence quenching efficiency, CPE chain aggregation (induced by the addition of either Ca2+ or H2O to methanol solution), and quencher molecular size. We propose that the superlinear Stern-Volmer quenching behavior typically observed in CPE-quencher systems arises due to quencher-induced aggregation of the CPE chains.

Biocidal Activity of Cationic Conjuguated Polyelectrolytes (CCPEs) and Oligomers

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Poly(phenyleneethynylene)-based CCPEs and oligomers bearing cationic functionality such as ammonium, DABCO and imidazolium groups synthesized in our lab showed excellent biocidal activity. These CCPEs are water-soluble and display very low cytotoxicity. Our investigation on their biocidal activity against various microorganisms such as Gram-negative and Gram-positive bacteria, and fungi planktonic cells and biofilms under visible-light-illumination revealed that these CCPEs are effective biocides at concentrations as low as 1 μM – 128 μM. The biocidal activity of these conjugated materials involves two main pathways: (1) the cationic segments in the side chains allow the CCPEs to electrostatically bind to the net-anionic membranes of the bacterial/fungi cell wall causing disruption, distortion and damage; and (2) upon irradiation with light, the conjugated backbone of CCPEs absorb light and photosensitize O2 to produce reactive oxygen species (ROS), which readily react with the cell wall and other cellular components that lead to rapid cell inactivation.

Biofunctional Conjugated Polyelectrolytes

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Related Recent Publications

Conjugated Polymer with Intrinsic Alkyne Units for Synergistically Enhanced Raman Imaging in Living Cells, Angew. Chem. Int. Ed. 201756, 13455–13458. DOI: 10.1002/anie.201707042

Huang; H. C. Pappas; L. Zhang; S. Wang; R. Cai; W. Tan; S. Wang; D. G. Whitten; K. S. Schanze “Selective Imaging and Inactivation of Bacteria over Mammalian Cells by Imidazolium-Substituted Polythiophene”, Chem. Mater. 201729, 6389–6395. DOI: 10.1021/acs.chemmater.7b01796

Wang; C. J. Zeman IV; J. Jiang; Z. Pan; K. S. Schanze “Intercalation of Alkynylplatinum(II) Terpyridine Complexes into a Helical Poly(phenylene ethynylene) Sulfonate: Application to Protein Sensing”, ACS Appl. Mater. Interfaces 20179, 33461–33469. DOI: 10.1021/acsami.7b01587

Y. Wang; S. D. Jett; J. Crum; K. S. Schanze; E. Y.; D. G. Whitten, Understanding the Dark and Light-Enhanced Bactericidal Action of Cationic Conjugated Polyelectrolytes and Oligomers. Langmuir 2013, 29, 781-792. DOI: 10.1021/la3044889