Hydrodynamic Properties of Aggregates

Hydrodynamic Properties of Aggregates where J is the Oseen tensor given by... 

The second part is devoted to adsorption of polyelectrolytes at interfaces and to flocculation and stabilization of particles in adsorbing polymer solutions. A recent theory of the electrostatic adsorption barrier, some typical experimental results, and new approaches for studying the kinetics of polyelectrolyte adsorption are presented in the first chapter of this part. In the following chapters, results are collected on the electrical and hydrodynamic properties of colloid-polyelectrolyte surface layers, giving information on the structure of adsorbed layers and their influence on the interactions between colloidal particles examples and mechanisms are analyzed of polyelectrolyte-induced stabilization and fragmentation of colloidal aggregates ... 

DLS was used to study the hydrodynamic properties of the end-functionalized copolymers. The zwitterionic polymers have a substancially defferent behavior than their precursors, due to the formation of aggregates in CCU. The values of the diffusion coeflScient at infinite dilution, D are lower, the Rh values higher and the aggregates are polydisperse. The ko values are negative in most cases, due to the aggregation process and is consistent with the low A2 values obtained by LALLS. 

This property is at odds with the ordinary concept of homogeneous density expected from the properties of porous or impermeable spheres and has important consequences for the hydrodynamic properties of fractal aggregates. Indeed, many previous studies based upon Stokes law have incorrectly calculated aggregate densities and porosities by considering aggregates as an assembly of permeable or impermeable spheres with a homogeneous distribution within the aggregate. 

Nguyen, H.P., Chopard, B. and Stoll, S. (2004). Hydrodynamic properties of fractal aggregates in 2D using lattice Boltzmann simulation. Future Gener. Comput. Syst. (FGCS), 20, 981-991. 

DLS is an established technique for protein characterization. For example, to And optimum protein crystalhzation conditions, DLS is used as a prescreening tool to identify critical parameters of the process such as the hydrodynamic size, polydispersity, and aggregation factors. DLS is also used as a method to characterize the hydrodynamic properties of globular proteins in electrolyte solutions. However, applications of DLS to characterize charged protein solutions, just as any other charged molecules in solution, could face certain difficulties in subsequent data treatment. 

Thus, plotting the static signal 5 as a function of the dynamic signal V yields a straight line, and its intercept gives the absolute aggregation rate constant. This analysis is now free of any assumptions about the optical or hydrodynamic properties of the dimer. However, the prerequisite is simultaneous availability of time-resolved SLS and DLS data. 

It should be noted, however, that for molecular species of geometries other than spheres, different approximations are needed to describe the hydrodynamic frictional coefficient, / [8]. Since there is a relationship between rg and the effective molecular size and shape of the molecular species, it is clear that diffusion coefficients are sensitive to the structural properties and aggregation modes of these species. Therefore, the diffusion coefficient can be used to probe binding phenomena and intermolecular interactions [10, 11]. 

---