Aggregation physics

The field of theoretical molecular sciences ranges from fundamental physical questions relevant to the molecular concept, through the statics and dynamics of isolated molecules, aggregates and materials, molecular properties and interactions, and the role of molecules in the biological sciences. Therefore, it involves the physical basis for geometric and electronic structure, states of aggregation, physical and chemical transformations, thermodynamic and kinetic properties, as well as unusual properties such as extreme flexibility or strong relativistic or quantum-field effects, extreme conditions such as intense radiation fields or interaction with the continuum, and the specificity ofbiochemical reactions. 

In the past, the equivalence between the size distribution generated by the Smoluchowski equation and simple statistical methods [9, 12, 40-42] was a source of some confusion. The Spouge proof and the numerical results obtained for the kinetics models with more complex aggregation physics, e.g., with a presence of substitution effects [43,44], revealed the non-equivalence of kinetics and statistical models of polymerization processes. More elaborated statistical models, however, with the complete analysis made repeatedly at small time intervals have been shown to produce polymer size distributions equivalent to those generated kinetically [45]. Recently, Faliagas [46] has demonstrated that the kinetics and statistical models which are both the mean-field models can be considered as special cases of a general stochastic Markov process. 

Of interest also are the results of applications of the Smoluchowski equation for systems with more complex aggregation physics than that provided by bilinear kernels. Leyvraz and Tschudi [32] conjectured that for the kernel ICy-fi) ) gelation occurs only when co > 1/2. The post-gelation behavior of a general system with a multiplicative kernel given by Eq. (60) has been analyzed by van Don-gen et al. [56]. By assuming that the distribution past the gel point could be expressed through that at t=tc, thus... 

Colloidal dispersions suspensions and aggregates Viscosity and transient electric birefringence study of clay colloidal aggregation. Physical Review E 65, 21407-21500... 

A. A. Kornyshev and S. Leikin. Electrostatic zipper motif for DNA aggregation. Physical Review Letters 82 4138-4141 (1999). 

Recent work identifies mixing during precipitant addition as a determinant of aggregate physical properties such effects are described with a floc-strength model. 

F. Argoul, A. Arneodo, J. Elezgaray, G. Grasseau and R. Murenzi, Wavelet Transform of Fractal Aggregates, Physics Letters. 135A (1989), 327-335. 

E. Freysz, B. Pouligny. F. Argoul and A. Arneodo, Optical Wavelet Transform of Fractal Aggregates, Physical Reviexf Letters. 64 (1990), 745-748. 

Dispersions of metallic nanoparticles can be obtained by two main methods (i) mechanic subdivision of metallic aggregates (physical method) or (ii) nucleation and growth of metallic atoms (chemical method). The physical method yields dispersions where the particle size distribution is very broad. Traditional colloids are typically larger (>10nm) and not reproducibly prepared, giving irreproducible catalytic activity. Chemical methods such as the reduction of metal salts is the most convenient way to control the size of the particles. Today, the key goal in the metal colloid area is the development of reproducible nanoparticle (or modem nanocluster) syntheses in opposition to traditional colloids. As previously reported, nanoclusters should be or have at least (i) specific size (1-10 nm), (ii) well-defined surface composition, (iii) reproducible synthesis and properties, and (iv) be isolable and redissolvable ( bottleable )- ... 

Gommes C J, Roberts A P (2008) Structure development of resorcinol-formaldehyde gels Microphase separation or colloid aggregation. Physical Review E 77 041409-041421... 

Tasong, W.A., Lynsdale, C.J., Cripps, J.C., 1998. Aggregate-cement paste interface I Influence of aggregate physical properties. Cement Concrete Res, 28(10) 1453-65. 

---