Properties and Applications of Phosphonium-Functionalized Conjugated Polyelectrolytes

Date

2024

Authors

Barboza Ramos, Isaí J.

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Abstract

The thesis herein explores the design, characterization, and functional properties of a series of novel poly (phenylene ethynylene) (PPE)-based phosphonium-functionalized conjugated polyelectrolytes (CPEs) for versatile applications in phosphate sensing and photodynamic therapeutics against pathogenic bacteria. The synthesis of the new class of CPEs was completed following the step-growth polymerization approach through the Sonogashira cross-coupling reaction. Moreover, the molecular weights of the polymers were estimated utilizing NMR diffusion-ordered spectroscopy (DOSY). Steady state and time-resolved fluorescence spectroscopy shed light on the optical properties and state of aggregation of the CPEs. The photophysical properties of the polymers are dependent on the lengths of the phosphonium pendant groups. Further fluorescence quenching studies demonstrated the efficient sensing response of the CPEs towards a set of nucleotides. The quenching effect is driven by electrostatic interactions that induce the formation of the polymer-quencher complex and instantaneous static quenching as principal mechanism. Notably, the polymer PPh-4-3C undergoes self-assembling in the presence of ATP, producing a chiral supramolecular structure that is originated by J-aggregation of the PPh-4-3C – ATP system. Given that the series of CPEs generate singlet oxygen and reactive oxygen species under light irradiation, in vitro antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria was evaluated. The results evidence profound light-activated antibacterial effects attributed to the bacterial membrane disruption, and a correlation between the dark bactericidal effect and the side chain lengths of the cationic pendant groups. Overall, the novel series of CPEs with phosphonium functionality represent a new platform of functional polymeric materials for relevant biological-related applications.

Description

The full text of this item is not available at this time because the author has placed this item under an embargo until May 16, 2026.

Keywords

Antibacterial activity, Conjugated polyelectrolytes, J-aggregation, Phosphonium functionality, Photodynamic therapy, Quenching effect

Citation

Department

Chemistry