Synthesis and Characterization of Branched Polyelectrolytes: Star-branched NaPSS

• Main Author: Holley, Daniel W.
• Format: Others
• Published: Trace: Tennessee Research and Creative Exchange 2009
• Subjects: Chemistry
• Online Access: http://trace.tennessee.edu/utk_graddiss/607

In this thesis, we examined the effect of branching on the solution characteristics of polyelectrolytes using a set of star-branched NaPSS. The polystyrene precursors to these polyelectrolytes were synthesized using anionic polymerization allowing for the production of three distinct groups of star-branched polystyrenes with varying functionality and arm length. Following sulfonation, several methods commonly employed in the literature for evaluation of sulfonation degree we established that sulfonation was quantitative. TGA was also demonstrated to reveal important characteristics of the sample. We used aqueous SEC coupled with a multiple angle light scattering detector to determine several molecular characteristics of the star-branched NaPSS samples. Linear NaPSS synthesized via radical polymerization and sulfonation of polystyrene were characterized and important differences between NaPSS synthesized by the two methods were established. Dynamic light scattering experiments established a qualitative link between the presence of a slow diffusive mode and the degree of sulfonation. The branching parameter g was determined for the star-branched NaPSS samples and compared to theoretical predictions. Static light scattering experiments were performed to elucidate the effect of Cs on the Rg, where it was determined that Rg ~ Cs-0.11 for the whole range of samples. The apparent persistence length was determined and relations were established for its variation as a function of Cs, f and degree of arm polymerization. Additionally, no agreement was found between theoretical predictions of g and experimentally determined ones. A method was developed that enabled the determination of molecular dimensions of star-branched NaPSS using AFM with a high degree of agreement with the radii established using scattering methods on solutions of the polymers. The intrinsic viscosity could reliably be determined in solutions with Cs using either a Huggins or Wolf equation. For solutions with no Cs, the Huggins equation fit over the data at low Cp was confirmed by AFM measurements of the dimensions of the polyelectrolyte and comparisons to the radius determined from the intrinsic viscosities calculated using the two equations to be more accurate. The values of g‟ were calculated for solutions of the NaPSS stars in water and compared with theory.