The problem is real, for example, in polymer industry. Micro and nano sized additives tend to aggregate. Their even distribution is always a challenge, especially in a viscous fluid. Which techniques are the best, and how to prove even distribution in low concentrations (0.01 - 0.001%)?
It depends on the chemical compositions of the host and the additives, as well as colloidal size distribution etc.
You can functionalist the surface to prevent aggregation, use surfactants, and try different infusion methods.
Without more specific examples, it is difficult to give a specific answer.
To prove an even distribution at low concentrations (0.01 - 0.001%) you may want to employ a technique that is sensitive to both long- (lets-say 5-12 nm) and short-range distances between the additives. In the past we have successfully used EPR to study initial aggregation phenomena of Gd3+ ions in silicate glasses (Smirnov, A. I., Sen, S. “High field EPR of Gd3+-doped glasses: line shapes and average ion distances in silicates”, J. Chem. Phys. 115 (6): 7650-7656 (2001)). If you are working with nitroxide-based compounds than EPR and/or DEER could be helpful.
Michael, thank you for the answer. It is clear that in every case one need certain interphase compounds/compatibilizers. The question is a bit more strategical and related to procedure (not chemcal nature). How would one evenly distribute 0.001% of nanotubes in a polymer? 0.001% of metal oxide in sand? 10 black balls in 10 000 000 white ones?
Hi Alex, thank you for the interesting example. ESR is certainly advantageous method in case you deal with paramagnetic species. I will have a look at the paper to find a method for even distribution Gd3+ in viscose glass melt, and also to see if the distribution was really even.
You usually will have to use a carrier, e.g. you mix something containing a few % of the stuff to be distributed with the material to be infused.
Titus, thank you. That should work, because sounds similar to stepwise dissolution approach, when one uses the main material as a carrier, mixes small portion and distribute that in bigger portion, and so on...
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