Kinetic Aspects Of Interaction Between Nanoparticles And Very Long Polymer Chains:
KINETIC ASPECTS OF INTERACTION BETWEEN NANOPARTICLES AND VERY LONG POLYMER CHAINS:
GOLD PARTICLES - POLYACRYLAMIDE SYSTEM
W. Nowicki
Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka ul. 6,
60-780 Poznan, Poland, e-mail: gwnow@main.amu.edu.pl
The introduction of very-high-molecular weight polyacrylamide (PAAm) into the hydrosol of nanosized gold particles initiates the process of aggregation between particles and macromolecules. A single macromolecule can attach a number of particles forming a multiplet. This number depends on the ratio between the particle and the polymer concentrations, the ionic strength of the medium and the incubation time.
A few stages in the process of aggregation of gold nanoparticles and very long chains of PAAm can be distinguished.
A study of the salt-induced coagulation of gold particles proceeding in the presence of PAAm has shown that the initial aggregation begins as a rapid process, which is collision-limited. After the attachment of few particles the process slows down considerably – after the first few minutes the relaxation time of particle-multiplet binding increases to about 2 hours, as observed in dynamic light scattering experiment. A considerable increase in the relaxation time of the attachament of subsequent particles probably reflects the time involved in the multiplet reconformation needed for the binding of an additional particle. As concluded from the changes in light extinction spectra of mixtures of gold hydrosol with PAAm solutions, a rearrangement of particles within multiplets takes place, leading to a reduction of interparticle distances. A mutual association of multiplets can also occur. The behavior of the system is affected by the presence of simple electrolytes.
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