Polystyrene translational diffusion coefficient

Fig. 16. Translational diffusion coefficient distributions G(D) of a simulated polymer mixture at two scattering angles ( , 17° and O , 14°). The mixture contains two polystyrene standards of distinctly different weight average molar masses (3.0 x 105 and 5.9 x 106 g/mol) and a high mass polystyrene...

Caroline and co-workers have recently reported measurements of translational diffusion coefficients in solutions of PS in two mixed-solvent systems at or near theta conditions. In the solvent CCb-methanol (85), they observed the diffusion theta state, defined when the coefficient y of Equation 41 equals 0.5, to occur at 25°C and a volume fraction of CCI4, (fyCCU = 0.8025. In this system there is strong preferential adsorption of the polymer for CCI4, and it is not possible to define a true theta state such that y = a = V2 and A2 = 0 simultaneously. Under diffusion theta conditions, the concentration dependence of Dt apparently is closely described by the Pyun-Fixman hard-sphere model. In the mixed solvent benzene—2 propanol, polystyrene exhibits a true theta condition at T = 25.5°C and (benzene) = 0.04. Frost and Caroline confirmed that y = 0.5 within experimental error in this system (86) and report that values of the parameter fcf are scattered between the extreme values corresponding to the predictions of Yamakawa (and Imai) and the soft-sphere model of Pyun-Fixman (or the Freed theory). 

Molecular weights M and M, mean square radii of gyration -(S translational diffuSion coefficients and hydrodynamic radii Rj of two series of crosslinked polystyrene in cyclohexane (cyclohex) at 34.5 and toluene at 20°C. The molecular weights of the two linear primary chains are M =188 OOO for S200 and M = 400 000 for S400. ... 

Polystyrene scattering experiments to determine translational diffusion coefficients and compare with linear chains. Mw 2 000-22 000 SANS experiments to determine mean [222]... 

Fig. 5.1 Weight average moleir mass (Af ) dependence of average translational diffusion coefficient ((D)) of hyperbranched polystyrenes with different subchain lengths in toluene at T = 25 °C, where (D) has a unit of cm /s and both Mw,s and Mw are expressed as g/mol ...

Fig. 14 The relationship between translational diffusion coefficient and gel concentration of polystyrene microgel at the swelling state [39].

Flow FFF is perhaps most promising in the area of water-soluble polymers. These polymers, which as a class are very difficult or impossible to separate by thermal FFF, can be fractionated according to diffusion coefficient or Stokes radius (which translate to molecular mass) in a flow FFF system using a water-compatible membrane such as cellulose acetate. Such a fractionation is shown in Figure 8.15, illustrating the programmed field separation of three sulphonated polystyrene components in a 510-//m-thick channel. The fact that the time of separation is somewhat longer than desired can be related to the excessive thickness of the channel, ten times thicker than the thinnest thermal FFF channel utilized. Recently we have been able to work successfully with a... 

Chapter 5 considers translation and rotation by solvent molecules in small-molecule liquids and polymer solutions. Correlations between solution properties are already more complex than might have been expected. At small rj, the diffusion coefficient and equivalent conductance of small-molecule probes in simple liquids scale as At larger rj, D and A are instead The boundary between small and large t] seen in the literature is uniformly near 5 cP. It is unclear why this particular value of r should not be system-specific. In contrast to smaU-molecule probes, mesoscopic probes such as polystyrene latex spheres in potentially highly viscous mixed solvents such as water glycerol retain D T/ri behavior over three or more orders of magnitude in rj. 

The values will be used in the sequel for the estimation of the characteristic time of the translation motion t and of the coefficient of the diffusion D of the polystyrene chains into solutions and melt. Accordingly to the experimental data the temperature dependence, estimated based on the elastic component of the viscosity Tj and parameter b, is described by the equations ... 

Let s use the obtained numerical values of the characteristic times of the segmental movement for the estimation of dynamical properties of the polystyrene chains that is their characteristic time of the translational movement t and coefficient of diffusion D into solutions and melt. Accordingly to Ref [25], the values t and D are determined by the expressions ... 

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