Characterization of Pressure-Induced Anisotropy in Atactic PolystyrenetextRott, DerekcreatorMathiowitz, EdithAdvisorMathiowitz, EdithReaderShukla, AnitaReaderHorrigan, DianaReaderBrown University. Department of Molecular Pharmacology, Physiology and Biotechnologysponsor2019x, 53 p.born digitalThesis (Sc. M.)--Brown University, 2019thesesAbstract of Characterization of Pressure-Induced Anisotropy in Atactic Polystyrene, by Derek Rott, ScM, Brown University, May 2019 Atactic polystyrene (aPS) is versatile and cheaply synthesized polymer used in a variety of commercial applications. This paper examines whether and under what conditions optical anisotropy and aPS chain alignment can be induced through a hot-pressing procedure. In this procedure, the polymer sample is heated above the glass transition (Tg), pressure is applied for a given period, and then the sample is cooled while maintaining pressure; in this study, temperature and time were varied while the force of compression was maintained at 20,000lbs. Hot-pressing induced birefringence which was qualitatively evaluated using polarized light films to reveal optically distinct regions within each sample. The specific heat-associated and kinetic thermal transitions of each distinct sample region were analyzed using temperature modulated differential scanning calorimetry and X-ray diffraction (XRD). No increase in Tg was observed in hot-pressed samples and thermal analysis did not show consistent evidence of other thermal transitions. XRD and hot stage XRD were used to observe the styrene peak through which the characteristics of the aPS backbone can be inferred. These measurements suggest that hot-pressing for brief periods at 125°C and 135°C induces alignment of the polymer backbone and sufficient energy to facilitate limited stacking of the styrene side chain groups, producing a more intense styrene peak compared to unpressed control samples. Hot-pressing below 125°C likely also induces backbone alignment without the stacking effect. This work contributes to the body of research on the photoelastic properties of aPS as well as the molecular motions induced by hot-pressing.Polystyrenemesophasehot-pressingEnglishRPB2019060310.26300/z6ds-t055In CopyrightCollection is open for research.