I am studying the adsorption behavior of polyelectrolytes on different carbon supports and catalyst in colloidal systems. Therefore I am trying to find a time-saving and reliable technique to obtain adsorption isotherms as alternative to very time-consuming techniques such as TGA.
The polyelectrolyte I am working with is a copolymer of styrene and vinylbenzylchloride functionalized with 1-methyl imidazole. Thoma et al. (2018) suggest density-measurements of the supernatant using a U-Tube oscillator, but this technique requires the use of relatively high concentrations/sample volumes, which is not possible in my case due to limitations of available materials.
Therefore, I was wondering if IR-spectrometric techniques are suitable for determining the concentration of polyelectrolyte in the supernatant.
I am very thankful for any suggestions and opinions.
Dear Andreas Gerstmayr, to the best of my knowledge, IR in its different forms is used mainly to probe the different interactions between the matrix, the counterion and the hydration shell. My Regards
I think you can perform IR and also try UV Vis Spectroscopy. The difference in the peak heights can be used for concentration calculation.
Hi;
In practice, FTIR spectroscopy has qualities that allow a wide range of analysis possibilities. The analysis will be qualitative to identify a compound from its spectral signature (complete spectral fingerprint) or to establish, by using evolutions of a restricted area of this fingerprint, fine changes of structure or molecular interactions depending on the energy levels "probed" by the radiation. In addition to the identification, the analysis will be quantitative allowing the dosage of a substance, thanks to the evolution of its spectral signature according to the quantity of measured matter.
With my best regards
Article Fourier Transform Infrared Spectroscopy Investigation of Wat...
for aqueous solutions it will not work, because of strong absorption for water. You may use it to study the amount and binding on adsorbent. UV-absorption of the aromatic moiety is much more characteristic and can be easily used to determine the amount adsorbed by analyzing the supernatant.
Thanks a lot to everyone for your help!
Titus Sobisch thanks for that suggestion. I previously thought about doing ATR-IR of the carbon black with adsorbed polyelectrolyte. I am not sure if it will be quantitative. And since carbon black is so extremely absorbant, I'd possibly need a Ge crystal to probe a more shallow space and reduce the absorbance. Also, are you sure it is impossible for just the polyelectrolyte aqueous systems? From what I understand water is a very difficult medium for such studies but nevertheless it is being done in various fields of research.
And thanks for the suggestion using UV-vis. I am not sure if UV could work though. It might depend on the solvent quality for my polyelectrolyte and become a problem if my polymer is forming larger aggregates. I found this paper
http://zeus.phys.uconn.edu/halld/tagger/fp-prototype/polystyrene_abs2.pdf
where they show decrease in phenyl-group absorbance in case of a worse solvent due to polymer entanglement, which reduces the UV absorbance.
Thanks again for your kind help everyone!
Hi, Andreas,
in case you do use aqueous media for adsorption experiments, measuring dissolved organic C using TOC analyzers might be easiest way to determine the concentration of non-adsorbed surfactants in solutions, not complicated by any aggregation and/or entaglement affecting potentially spectral properties. It does not work in organic solvents, however, all adsorption picture from organic solvents will anyway be differing from that in aqueous media