New sensor applications of poly(phenylene ethynylene)s

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004.Vita.Includes bibliographical references.(cont.) Fluorescence quenching by these analytes was shown to be assisted by specific host-guest interactions involving the calix[4]arene macrocycles.The principle of energy migration in conjugated polymers has been shown to have broad applicability to the design of sensors capable of detecting a variety of analytes. The infinitely customizable nature of these materials makes them powerful building blocks for a new generation of fluorescent sensors that exploit intricate chemical and photophysical effects to maximize sensitivity and selectivity. This dissertation discusses three new sensor applications of poly(phenylene ethynylene)s (PPEs) that make use of their chemical and photophysical properties to elicit fluorescence changes in response to analytes. A series of water-soluble carboxylate-functionalized PPEs has been prepared in which the carboxylate groups are attached to the polymer backbone by means of oligoethylene glycol spacers. The fluorescence properties of these polymers are strongly dependent on ionic strength and surfactant concentration, and the polymers can be activated and coupled to amine-containing biomolecules in solution. This technique has been used to generate a quenched polymer-peptide system that functions as a 'turn-on' fluorescence sensor for trypsin. Highly fluorescent PPE films on glass slides and silica microspheres have been prepared by electrostatic layer-by-layer assembly of a polyanionic PPE. These films are capable of efficiently transferring energy to dye-labeled polycations adsorbed to the film surface. Suspensions of PPE-coated microspheres have been used for the detection of quenchers in aqueous solution and show up to 200-fold sensitivity enhancements versus similar dissolved polymers. A series of calix[4]arene-functionalized PPEs have been synthesized and used for the detection of the Ba²⁺ and N-methylquinolinium ions in solution.by Jordan Howard Wosnick.Ph.D