- PDMS gels are produced by irradiation with accelerated electrons. Traces of radicals might still be present. If your molecule of interest is instable with respect to organic radicals it might be useful to add traces of radical scavenger to the solvent prior to adding the valuable sample.
- Stretched PDMS gels typically survive several months. However, over longer time the alignment properties can be lost.
- Some solutes do not diffuse into PDMS gels. There are two possible reasons for this: a) The gel is too strongly cross-linked. In this case chose a PDMS stick with lower irradiation dose. b) The solute is soluble in the organic solvent used, but not at all soluble in PDMS (water for example does not diffuse into a PDMS gel). In this case a different polymer has to be used for alignment that suites the solubility properties of the solute.
- If you have used a PDMS gel for a publication, please cite the following references:
B. Luy, K. Kobzar, H. Kessler, Angew. Chem. 116, 1112-1115 (2004); Angew. Chem. Int. Ed. 43, 1092-1094 (2004)
J. C. Freudenberger, P. Spiteller, R. Bauer, H. Kessler, B. Luy, J. Am. Chem. Soc. 126, 14690 - 14691 (2004).
PDMS strongly sticks to all kinds of glass. The insertion of polymer sticks into the NMR-tubes therefore needs special treatment. An easy way is to cool down PDMS and the glass tube using either dry ice or liquid nitrogen. Cold PDMS can be pushed gently into the cold NMR tube with a suitable stick (plastic or glass, peace of wire, straw, whatsoever). If PDMS still sticks to the glass DO NOT PUSH VIOLENTLY, the gel might get destroyed. Instead take the NMR-tube with PDMS half way inside and let it sit on dry ice or liquid nitrogen for another few minutes until it moves easily to the bottom of the tube.
Take care, that after adding the solvent your gel does not swim on top!
The time it needs to equilibrate depends strongly on the viscosity of the solvent and spreads from one day to few weeks.