Structural Influences on the Photochemistry and Photophysical Properties of p-Phenylene Ethynylenes: Aggregation Effects and Solvent Interactions

Compounds based on the p-phenylene ethynylene backbone with pendant charged groups, known as conjugated polyelectrolytes, have been of particular interest in recent years due to their solubility in water, sensing properties, and biocidal activity against bacteria, viruses, and fungi. A series of oligomers based on these polymers were synthesized (OPEs), and several interesting questions about their photophysical and biocidal properties were raised by earlier experimental observations, which are addressed by this dissertation. The study initially focuses on the influence of the backbone length and presence of carboxyester substituents on the photophysical properties of the OPEs. Next, the photochemistry of the OPEs is explored as the products and mechanisms are elucidated through isotopic studies with mass spectrometry, revealing that photo-protonation by water and addition of oxygen across the triple bond are the two dominant initial mechanisms of all major pathways in aqueous solution. Finally, the aggregation of OPEs with is studied in two systems: surfactants and model bacterial membranes. The placement of the ionic alkyl substituents played a dominant role in determining the outcome of molecular interactions and type of aggregates which resulted between OPEs and both systems. Biophysical simulations of the interactions between OPEs and these two systems provided mechanistic insight into the mechanism of bacterial membrane disruption and the attenuation of photodegradation observed with OPE-surfactant complexes. In addition to determining the OPEs could be protected from photolysis and the structural basis for aggregate type, surfactant complexation was used to form a biocidal complex from a non-biocidal anionic OPE. The work presented will be of great use for future developments in sensors, biocides, photo-resistant materials, and drug delivery applications

NASA Tech Briefs, February 1993

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NASA thesaurus. Volume 1: Hierarchical Listing

There are over 17,000 postable terms and nearly 4,000 nonpostable terms approved for use in the NASA scientific and technical information system in the Hierarchical Listing of the NASA Thesaurus. The generic structure is presented for many terms. The broader term and narrower term relationships are shown in an indented fashion that illustrates the generic structure better than the more widely used BT and NT listings. Related terms are generously applied, thus enhancing the usefulness of the Hierarchical Listing. Greater access to the Hierarchical Listing may be achieved with the collateral use of Volume 2 - Access Vocabulary and Volume 3 - Definitions