I'm working with choline-based ionic liquids where the anions differ from: acetate, hexanoate, isobutyrate and propionate. I analyzed the contact angle using water droplet and obtained increased contact angle in the order i described the anions. How can a relate the contact angle with hydrophilicity (all angles were below 90º)?
Thanks in advance :)
Hydrophilicity should rise in order hexanoate< isobutyrate
Ionic liquids with the tosylate anion tend to be very water soluble and have high polarizability, I'm not sure about hydrophilicity, but I believe it may follow polarizability. The following paper is about the correlation of structure of ionic liquids and it's proprieties, it might be helpful.
Article Correlation of molecular structure and polarity of ionic liquids
Dear Carolina Pereira,
In my opinion, Hydrophilicity or hydrophobicity depends on ionic size. Therefore, the anions with small ionic radius considered as more hydrophilic. While ions with larger ionic radius considered as an hydrophobic nature.
Idea "While ions with larger ionic radius considered as an hydrophobic nature" is not true in part. Tetramethylguanidine and diisopropylamine have practically identical size but its LogP (quantitative hydrophilicity measure) are essentially different (in some units )
More impressive examples are anions of heteropolyacids - very large by volume (ionic radius) but hydrophilic at the same time. Type of atoms(bonds) of molecule is very important.
The question is not only the anion size, but hydrogen bond ability and charge distribution as well. Since all your anions are from the same class, in this case size will be the dominating effect, but something like chloride will be even more hydrophilic.
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