Quintuple-Detector Size-Exclusion Chromatography Characterization of Copolymers and Polymer Blends

• Other Authors: Rowland, Steven M. (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Chemistry; Biochemistry
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-5943

The work described in this thesis details the development of a quintuple-detector SEC separation to measure chemical heterogeneity and determine the solution conformation for copolymers and polymer blends. Chemical heterogeneity affects the accuracy of static light scattering (SLS) and differential refractometry (DRI) data, which are both widely used for polymer characterization. The ability to measure chemical heterogeneity allows for the determination of chemical-heterogeneity-corrected values of molar mass (M); M, size, and intrinsic viscosity [n] statistical averages; molar mass distributions (MMD); and determinations of polymer solution conformation. This thesis outlines a novel approach for the measurement of chemical heterogeneity, by utilizing UV and DRI detectors, for two component polymer systems in which both functionalities absorb radiation in the same range of the UV spectrum. This information was not obtainable by previous methods, which were limited to polymer systems in which only one functionality absorbed in the UV region. We also introduce an, on-line, quintuple-detector scheme that allows for the determination of copolymer and blend solution conformation via four, unrelated, parameters: RG conformation, Mark-Houwink, ρ-parameter, and Rn/RG plots. These four parameters utilize the combination of data from multiple detectors to obtain information about polymer conformation that is not accessible by any one detector alone. A poly(acrylamide-co-N,N-dimethyl acrylamide ) copolymer and two blend samples, 1:1 and 1:3 blends of polyacrylamide (PAM) and poly(N,N-dimethyl acrylamide), were studied via this quintuple-detector method. We were able to show that the copolymer ranged in percentage composition from ~73-90% DMAM and that the copolymer conformation transitioned from an extended coil structure to a random coil conformation with increasing M. We also showed that the determination of conformation via RG and RH conformation plots were not sensitive to this change in conformation; however, the combination of MALS, QELS, and DRI detectors provided three methods that identified the transition in conformation and were all in good agreement as to the M region of transition. Chemical heterogeneity measurement for the blends identifies the regions that are rich in the respective components of the blends, thereby providing information about the distribution of the component homopolymers in the blend MMD. The Mark-Houwink and Rn plots confirms that the conformation of the 1:3 PAM/PDMAM blend is that of a random coil, which was expected since both homopolymers were also random coils under the given solvent and temperature conditions. === A Thesis submitted to the Department of Chemistry in partial fulfillment of the requirements for the degree of Master of Science. === Fall Semester, 2011. === August 1, 2011. === Chemical Heterogeneity, Copolymers, Light Scattering, SEC, Size-exclusion Chromatography === Includes bibliographical references. === André M. Striegel, Professor Directing Thesis; Michael Roper, Committee Member; Scott Stagg, Committee Member.