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Published on-line at 07:06:53 PM on Tuesday, April 16th, 2013
High Pressure Physics: a route to the synthesis of novel nano-composite materials
High pressure and UV radiation to obtain a totally new nano-composite material: PESIL.
New ideas come out by merging High Pressure Physics and Chemistry with the realm of meso/micro-porous solids such as zeolites. These solids are complex materials having an impressive range of large scale applications such as, among others, fine gas separation, gas storage and catalysis. In fact, Dr. Santoro (IFAC-CNR) and Dr. Gorelli (IPCF-CNR) together with Prof. Bini (LENS) and colleagues of the CNRS in Montpellier, have recently used zeolites in a completely new fashion. This team has photo-polymerized ethylene using non-catalytic high pressure techniques at 0.5-1.5 GPa under UV (351-364 nm) irradiation on a sub-nanometer scale in the channels of a pure SiO2 zeolite, silicalite, in order to obtain a unique nano-composite material with drastically modified mechanical properties.
The structure obtained contains single polyethylene chains, which adapt very well to the confining channels as shown by optical spectroscopy and X-ray diffraction. The new material has been baptized PESIL from PE (polyethylene) and SIL (silicalite). The formation of PESIL results in significant increases in bulk modulus and density and the thermal expansion coefficient changes sign from negative to positive with respect to silicalite. Mechanical properties may thus be tuned by varying the amount of polymerized ethylene, and it can be easily foreseen the potential of obtaining a version of PESIL with null thermal expansion coefficient! The applications of this material would be compelling in the field of precision mechanics.
The potential high pressure, catalyst free synthesis of nano-composite materials similar to PESIL, but based on conducting polymers along with the potential high pressure functionalization of zeolite micro-channels could open the way to an entirely new class of micro/nano-structured materials uniquely suited for advanced electronic and photonic applications. For instance, high pressure polymerization could lead to the incorporation of conducting polymers, such as polyacetylene, which would be well protected in the zeolite matrices and are not chemically stable otherwise. This would in turn result in the production of novel, ideal conducting organic/inorganic composite materials.
Source: Nature Communications
- High-pressure synthesis of a polyethylene/zeolite nano-composite material
- Santoro, M Gorelli, FA Bini, R Haines, J van der Lee, A
- NATURE COMMUNICATIONS
- Vol. 4, Issue: na, pages: na-na, Article Number: 1557, MAR 5 2013, DOI: 10.1038/ncomms2564
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