Desorption spectrometry II: coupled desorption of Li marker and degradation of polypyrrole

Abstract

In this work, different aqueous Lithium salt markers were introduced into polypyrrole, thereafter the system was dried, and finally water was again allowed to enter with the aim to desorb the incorporated Li marker. The Li desorption is closely followed by the Neutron Depth Profiling technique. It turns out that the desorption spectra strongly depend on the solubility of the applied markers, and furthermore, the polymer-water interaction influences the outcome. Finally, there are hints that the Li markers incorporated within the polymeric free volume may undergo chemical bonds with the polymer. Especially the desorption of incorporated LiF from the polymer leads to very peculiar Li depth distributions which closely resemble the well-known Case II diffusion profiles, with steep profile concentration changes emerging at the front of the water penetration from the outside.

KEYWORDS:

• Porosity
• polypyrrole
• tracer technique
• lithium salts
• desorption
• neutron depth profiling

Acknowledgements

We are indebted to Prof. D. Fink for all the help, advice and consultation, and to Prof. H. Naamann for providing us with the PPy foils. Thanks also to the team of the Berlin research reactor BER II – it was possible to perform preliminary measurements some time ago.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 In fact, experiments with enzyme-clad (hence neutral) nanopores point at this (10,11).

2 This sharp marker concentration front resembles somewhat the sharp concentration fronts observed in Case II diffusion-type studies (12). In the latter cases often phase transitions (such as glassy-to-rubbery transitions in the case of polymeric samples) are the underlying reasons for the build-up of such sharp profile shapes. This is replaced here by the slow transition from solid to dissolved LiF.

Additional information

Funding

The experiments were carried out at the ‘CANAM’ infrastructure, as well as at the infrastructure of ‘Experimental nuclear reactors LVR-15 and LR-0’ in Rez, both supported by the Ministry of Education, Youth and Sports under the Projects No. LM2015056 and No. LM2015074, respectively. Financial support is acknowledged by the Grant Agency of the Czech Republic (contract No. 18-07619S).