Wyniki wyszukiwania - BazTech

Ograniczanie wyników

1 Wiadomości Chemiczne

1 2001

Znaleziono wyników: 1

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: stabilizacja dyspersji

Sortuj według:

Ogranicz wyniki do:

Wpływ polimerów na właściwości układów dyspersyjnych zawierających nanocząstki

Nowicki W., Nowicka G.

Wiadomości Chemiczne

2001

[Z] 55, 5-6

547--565

The stability of colloidal dispersions is often modified by addition of polymers which, depending on the conditions, can induce repulsion or attraction between particles. The repulsion contributes to the stabilization of dispersions, whereas the interparticle attraction results in the dispersion flocculation. These phenomena are of great importance in many biological, medical, environmental, and chemical industrial processes and they attract much of scientific interest. The main mechanisms of the processes which are induced both by nonionic polymers and polyelectrolytes as well as adsorbing and nonadsorbing macromolecules, are briefly reviewed in this paper. In the majority of systems in which stabilization/flocculation processes were studied, the colloidal particles were large, compared with the radii of gyration of macromolecules. On the other hand, it was found that interactions between very small colloidal particles and large polymer molecules are important in such areas like the water and waste water purification and paper manufacture. They also play a major role in biological systems. The systems composed of very small particles and large macromolecules have been found to reveal a number of original features. The relative size of macromolecules and particles has a significant effect on the conformation of the polymer adsorbed, the interparticle interaction and the structure of aggregates formed. When colloidal particles are smaller than the macromolecules then a single particle accommodates only a part of the polymer chain, the rest of the molecule extends far away from the particle as a long end which can adsorb on the free surface of other particles. Multiplets composed of a number of particles attached to a single polymer molecule are formed. Properties of these multiplets determine the phase behavior of the system; if further association takes place the macroscopic phase separation is observed, otherwise the suspension is stable. Primarily, the interactions between the multiplets depend on their structures which, in turn, are determined by numerous factors like the polymer-to-particle number concentration, adsorption affinity, particle interactions, architecture and conformations of polymer molecules, and others. A number of models of the adsorption of large macromolecules on very small colloidal particles and the flocculation and stabilization processes of fine suspensions by high-molecular-weight polymers were proposed. The mode of action of very long polymer chains on fine suspensions was studied with computer simulations. The floc structures and formation kinetics were investigated as a function of polymer/particle concentration ratio and the chain conformation.