The behavior of fluorescently-labelled poly(dimethylsiloxane) oligomers in environmentally friendly solvent systems
Gardinier, Wendy E
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There have been several studies on a wide range of polymers aiming to determine their behavior under various conditions. It is important to understand these systems to most effectively advance our technological capabilities. We have chosen to study poly(dimethylsiloxane) (PDMS), oligomes under a variety of conditions. We have labeled the oligomer chain termini with the fluorescent probe, pyrene (Py). In this way we can easily determine the local micro-environment at the tail and explore the tail dynamics. This dissertation provides an in-depth study of the aforementioned polymer in two neoteric solvents, supercritical carbon dioxide (scCO 2 ) and room-temperature ionic liquids (RTILs). We have explored the possibility of continuously tuning the solvent quality by studying the effect of added CO 2 , temperature, and co-solvent. Previous work by our group has studied this polymer in a "good" solvent (toluene). In this dissertation, we have investigated the Py-PDMS-Py behavior in "theta" (ethyl acetate) and "poor" (methanol) solvents as a function of temperature and added carbon dioxide (CO 2 ). Steady-state and time-resolved fluorescence are used to determine how changes to the solvent affect the local microenvironment that surround the Py probes, the tail-tail cyclization dynamics, the potential of oligomer-oligomer interactions, and the mean tail-tail distance as a function of added CO 2 , temperature, or co-solvent. Additionally, my research efforts have centered on determining the behavior of pyrene-labeled poly(dimethylsiloxane) (Py-PDMS-Py) in RTILs to better understand polymerization reactions within RTILs. In this dissertation, two RTILs, 1-butyl-3-methyl-imidazolium bis(trifluoromethyl)sulfonyl imide ([bmim][Tf 2 N]) and 1-butyl-3-methylimidazolium bis(perfluoroethylsulfonyl)imide ([bmim][beti]) were used in order to explore the photophysics of Py-PDMS-Py as a function of temperature and co-solvent.