Multicomponent Polymer Systems: Polymer Compositional Analysis using Low-Field 1H-NMR Spectroscopy and Tuning the Compositional Drift in Styrene/Isoprene Anionic Copolymerizations
Bukkapatna Chakrapani, Sneha
Type of DegreeMaster's Thesis
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This Thesis investigates multicomponent polymer systems in the context of their characterization and their synthesis. The composition of the different polymers comprising multicomponent polymer systems is a vital variable in tuning their properties. Herein, low-field 1H NMR Spectroscopy (60 MHz), a newly commercially available technology, is inspected as a possible low-cost alternative to the significantly more expensive (in terms of capital and maintenance costs) higher-field NMR spectrometers (> 250 MHz) for the compositional analysis of multicomponent polymer systems, namely polymer blends and block copolymers. The results from a low-field spectrometer are corroborated using a high-field spectrometer and are found to be adequately quantitative within the typical confidence for compositional analyses of this nature using traditional high-field NMR spectroscopy. Next, a series of copolymers of styrene and isoprene are synthesized by anionic copolymerization using a co-solvent mixture of cyclohexane and triethylamine, of varied relative compositions to probe the impact on compositional drift (statistical composition along the polymer chain). Copolymerization reactions are monitored online using in-situ Attenuated-Total-Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) to obtain monomer conversions as well as overall conversions in order to completely describe the copolymer compositional profiles. Compositional drift profiles are used to extract reactivity ratios using the Beckingham-Sanoja-Lynd approach to define the copolymer architecture and as a quantitative means of comparison. Conclusively, this system allows for the tuning of copolymer compositional profiles as desired with potential applications in designing polymer architectures with desired properties.