High-Pressure Synthesis and Gas-Sensing Tests of 1-D Polymer/Aluminophosphate Nanocomposites

Tuning Negative Thermal Expansion in AlPO4-17 by Insertion of Guest Molecules

The very strong negative thermal expansion in the porous aluminophosphate AlPO₄-17 with a hexagonal erionite structure was tuned by the insertion of oxygen molecules at high pressure. The structure of the oxygen-filled material was determined in situ at high pressure by synchrotron, single-crystal X-ray diffraction. The thermal expansion of this material was measured precisely at 0.38 GPa by synchrotron X-ray powder diffraction. Whereas the overall volume thermal expansion only exhibits a small change with respect to empty AlPO₄-17 at ambient pressure, the expansion along the a direction decreases almost to zero and the expansion along c increases by a factor of 7. Such highly anisotropic thermal expansion properties are of great interest for mechanical and optical applications as in two directions the dimensions of the material are extremely stable, whereas a very strong linear negative thermal expansion of -2.2 × 10^-5 K^-1 is observed in the perpendicular direction. Guest insertion is thus a very powerful tool for tuning the thermal expansion properties of porous materials.

Synthesis of a polyphenylacetylene/silica nanotube composite under high-temperature, high-pressure conditions

Phenylacetylene was inserted and polymerized in 5 nm diameter silica nanotubes under high pressure – high temperature conditions of 0.5 GPa and 437 K in an inert gas. The resulting nanocomposite was characterized by infrared and Raman spectroscopy and scanning and transmission electron microscopy. The vibrational spectroscopic data confirmed the formation of π-conjugated polyphenylacetylene and the absence of crystallization of the amorphous nanotubes. Scanning transmission electron microscopy coupled with energy dispersive x-ray spectroscopy, STEM-EDX, measurements confirmed the insertion of the polymer in the channels of the nanotubes and electron diffraction confirmed the amorphous nature of both the polymer and the host SiO2 nanotubes. The obtained nanocomposite is a candidate material for gas sensing applications. Du phénylacétylène a été inséré puis polymérisé dans des nanotubes de silice de diamètre 5nm dans de conditions de haute pression 0,5 GPa et haute température 437K. Le nanocomposite obtenu a été caractérisé par spectroscopies infrarouge et Raman et par microscopies électronique à balayage et en transmission. Les données de spectroscopie vibrationnelle ont confirmé la formation de polyphénylacétylène π-conjugué ainsi que l’absence de cristallisation des nanotubes amorphes. La microscopie électronique en transmission à balayage, couplée à la spectroscopie des rayons X en dispersion d’énergie a confirmé l’insertion du polymère à l’intérieur des canaux des nanotubes. La diffraction électronique a confirmé la nature amorphe du polymère et des nanotubes de SiO2 hôte. Le nanocomposite est un candidat comme matériau pour les capteurs de gaz.

High-pressure, high-temperature synthesis of nanostructured polydiphenylbutadiyne confined in the 1-dimensional pores of single crystal AlPO4-54

Diphenylbutadiyne was inserted and polymerized in porous AlPO4-54 single crystals under high temperature, high pressure conditions to form a confined, nanostructured π-conjugated polymer.