# Low-volatile liquids that 'ball-up' on siliconoxide or perfluoroalkanes

This is a very simple and short question. I am looking for liquids that are low/non-volatile at 20$^\circ$C (at least substantially less volatile than water) which have a high contact angle with glass and oxidized silicon (in air) or with a coating of perfluoroalkanes (specifically Perfluorodecyltrichlorosilane).

The requirement on the contact angle is say $\theta>70^\circ$, i.e. the liquid should 'ball-up' a bit. The reason I am asking is that I cannot seem to find any (common) liquids that have both the low-volatility and the high contact angle $\theta$. Does anyone know some examples? Or, if no such thing exists, can someone explain what the fundamental reason is that these liquids don't exist?

## 1 Answer

Here it comes... mercury. 75-wt% Ga 25 wti%, mp. 15.5 C and

http://en.wikipedia.org/wiki/Galinstan

in general wet glass. Maybe ionic liquids,

J. Am. Chem. Soc. 129(13), 3804 (2007), DOI: 10.1021/ja070169d
Aust. J. Chem. 57(2) 113-155 (2004)

http://www.ppmp.pwr.wroc.pl/sorpa/file/eee7c6b05fb9497a9a59507ca0346479/download
[DMIM][Cl], 1,3-Dimethylimidazolium chloride, is reported 105.9 contact angle on glass. That might be a typo - it's a huge number for the class of compound.

• Also consider putting one or a pair of really long alkyl groups on the imidazolium to make it greasy toward glass, and with a bis(trifluoromethanesulfonyl)imide counterion. – Uncle Al Mar 25 '14 at 18:00
• Sulfate appears to be the internal binding energy opposite (very high) of bis(trifluoromethanesulfonyl)imide anion (very low), giving much larger surface tensions. – Uncle Al Mar 26 '14 at 20:28