High Pressure Physics and Chemistry in Nanoconfined Systems

In the recent years it has been achieved the high pressure (GPa) polymerization of simple organic molecules in the nanochannels of pure SiO2 zeolites [1,2], leading to the formation of novel composite materials which are recovered to ambient P and have remarkable properties. A polyethyelene/silicalite composite, PESIL, was formed with tunable thermo-mechanical properties and potential null thermal expansion. Then we obtained a conjugated chain/silicalite composite, PASIL, where branched, semiconducting oligomers are buried in the host, protecting zeolite. I will briefly review on all this matter and then present our recent, unpublished results on the formation of 1D conducting polymers, true polyacetylene (PA) in this case, in the 1D host channels of ZSM-22. In this composite the electronic density of state of PA is expected to exhibit van Hove singularities related to quantum 1D confinement, which could lead to future technological exploitations. I will then show results on the polymerization of CO in SiO2 zeolites, which seems leading to more stoichiometrically and structurally ordered polymers then obtained so far in the bulk, high pressure polymerization of this simple system. The polyCO/zeolite composite could be an interesting energetic material. Finally, I will show the case of dense, molecular oxygen, which was confined (GPa) in silicalite. In this case, what we are looking for is not a polymerization, but rather the potential anti-ferromagnetic, low dimensional order of the confined molecules due to the S=1 spin of O2. This group of experimental studies is based on the diamond anvil cell (DAC), and in situ IR and Raman spectroscopy and single crystal and powder, both laboratory and synchrotron X-ray diffraction. [1] M. Santoro, F. A. Gorelli, R. Bini, J. Haines, and A. van der Lee, High-pressure synthesis of a polyethylene/zeolite nano-composite material, Nature Communications 4, 1557 (2013). DOI: 10.1038/ncomms2564. [2] D. Scelta, M. Ceppatelli, M. Santoro, R. Bini, F. A. Gorelli, A. Perucchi, M. Mezouar, A. van der Lee, and J. Haines, High Pressure Polymerization in a Confined Space: Conjugated Chain/Zeolite Nanocomposite, Chem. Mater. 26, 2249-2255 (2014).