| By using analytical ultracentrifuge (AUC) as the main technique, we have examined the sedimentation and diffusion behavior of neutral polymers and polyelectrolytes in solution. Our results show that AUC is a powerful tool to study the dynamics of polymers including polyelectrolytes. The thesis describes the following studies.Firstly, we have inverstigated the sedimentation and diffusion of poly(ethylene glycol) (PEG) with molar mass (Mw) from 5.0×102 to 2.0×105 g/mol. The sedimentation velocity analysis based on Lamm equation gives the sedimentation coefficient (s) and diffusion coefficient (D). Our study reveals that the sedimentation coefficient (s0) and diffusion coefficient (D0) at infinite dilution scale to Mw. Namely, s0 = KsMwαwith Ks = 6.14×10-3 andα= 0.469±0.008, and D0 = KDMw-β with KD = 1.43×10-8 andβ= 0.576±0.007, respectively.Secondly, we have studied the dynamics of poly(sodium styrenesulfonate) (PSSNa) in aqueous solutions with and without added salt (NaCl) by AUC via sedimentation velocity (SV) as a function of NaCl concentration (Cs) or PSSNa concentration (Cp). It is found that as Cs increases, s monotonically increases, whereas D shows a minimum. On the other hand, as Cp increases, s decreases while D exhibits a minimum at Cs < 1.0×10-3 M. However, they linearly vary with Cp at Cs > 1.0×10-3 M. The scaling relation between Mw and s0 or D0 indicates that PSSNa chain changes from an extended rod to a random coil as Cs increases. The sedimentation of PSSNa in semidilute solutions has been studied as well. In a solution without added salt or a low salt solution, as Cp increases, s decreases and exhibits two transitions corresponding to the overlap concentration (C*) and entanglement concentration (Ce), and either C* or Ce increases with Cs. When Cs is high enough, the electrostatic interactions are screened, s slightly varies with Cp at Cp < C*. However, s decreases with Cp at Cp > C* with s Cp-α, where the scaling indexαhas dependence on Cs but not on Mw. Our experiments demonstrate that the dynamics of polyelectrolyte chains is mediated by interchain electrostatic repulsion, hydrodynamic interactions and intrinsic excluded volume effect.Thirdly, we have examined the specific ion effect on the sedimentation of P4VPI. I- associates with pyridine in solution, which can cause the aggregation of P4VPI chains. The aggregates are stable in a solution with a lower [I-]. P4VPI chains form precipitates when [I-] is above a critical value. The interaction between P4VPI and Cl- or Br- is much weaker than I-. However, Cl- or Br- can disassociate the complex of pyridine with I- if [Cl-] or [Br-] is high enough.
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