High Pressure Polymerization in a Confined Space: Conjugated Chain/Zeolite Nanocomposites

Conducting polymers are one of the most promising classes of materials for enabling technologies such as solar energy conversion, organic electronics, and opto-electronics. The text-book conducting polymer is polyacetylene, which is difficult to synthesize in the all-conjugated form and also reacts with atmospheric moisture. Zeolites, widely used in diverse fields, could provide the ideal microporous framework capable of driving the ordered polymerization of acetylene. Also, the embedded polymer would be chemically protected by the zeolite, resulting in a unique organic/inorganic, conducting nanocomposite. We polymerized acetylene in the channels of a noncatalytic, pure SiO2 zeolite, silicalite in a diamond anvil cell, using only high pressure (~4 GPa) as the driving force. A unique nanocomposite was obtained and recovered at ambient pressure, made of conjugated chains embedded in the silicalite as determined by combining different techniques: IR spectroscopy, Raman spectroscopy and microscopy, and X-ray diffraction. We thus made the first step toward the synthesis of a new generation of conducting polymers embedded in nanostructured hosts and also added to the development of mechanochemistry in highly confined systems.