I am looking for compounds that are liquid at normal temperatures and are physically very large, to be used in an ellipsometer adsorption experiment. I am currently working with decane. The candidates will ideally not be toxic or radioactive (such as $\ce{UF6}$).

  • $\begingroup$ What about solutions of proteins? Human serum albumin or something even larger? $\endgroup$ Jun 16, 2017 at 12:38
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    $\begingroup$ You need a molecule with weak intermolecular forces and low symmetry. $\endgroup$
    – gsurfer04
    Jun 16, 2017 at 13:27
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    $\begingroup$ en.wikipedia.org/wiki/Polydimethylsiloxane ? $\endgroup$
    – Mithoron
    Jun 16, 2017 at 13:49
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    $\begingroup$ Dirk - what are you looking for the molecule to do in your experiment? Provide the largest change per molecule in psi and delta, or what? Presumably a visible ellipsometer, not IR or UV? $\endgroup$
    – Jon Custer
    Jun 16, 2017 at 13:51
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    $\begingroup$ Look for liquid crystal molecules, many are large, for example those based on porphyrins. $\endgroup$
    – porphyrin
    Jun 16, 2017 at 19:03

1 Answer 1


You may give porphyrins a try. These dyes are of interest for molecular electronics, and to render them less crystalline / more glassy, alkyl chains are attached to the central motif. One recent example are the room temperature liquid porphyrins developed in the group around professor Gryko:

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(source, Chem Asian J. 2010, 5, 904-909; doi: 10.1002/asia.200900693.)

Besides standard spectroscopic characterisation, the publication contains the results of DSC:

enter image description here

so compound 4d ($\ce{C176H294N4O12}$) may be a good candidate for an organic molecule, without charges and metal coordination, and suitable for ellipsometry / VASE measurments on surfaces.


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