Poly(N-isopropylacrylamide) (PNIPAM) is a thermo-responsive hydrogel; that is, it is a macromolecule which exists in a hydrated state beneath its lower critical solution temperature (LCST). Polymers such as PNIPAM undergo a phase transition in response to changes in temperature, pressure, pH, salt concentration, and the addition of co-solvents. Previously, visible-light microscopic measurements of the pressure-induced phase transition have been hindered by the lack of a pressurization apparatus with the short working distance and optical transmission properties necessary for high resolution microscopy. We employ a high pressure setup which uses a fused silica micro-capillary to contain the sample. Our experiment reveals differences in the spatial evolution of the phase change across the temperature and pressure thresholds, and Raman measurements allude to conformational differences in the evolution of the phase transitions. The Raman peaks positions are in agreement with previous FTIR measurements, and due to a difference in selection rules additional vibrational bands are observed in the Raman spectra.
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Bachelor of Science (B.S.)
College of Sciences
Dissertations, Academic -- Sciences; Sciences -- Dissertations, Academic
Length of Campus-only Access
Honors in the Major Thesis
Cariker, Coleman, "Pressure and Temperature Response of a Stimuli-Responsive Polymer Probed with Raman Microscopy" (2014). HIM 1990-2015. 1661.