APPLICATION OF POLYMER SWELLING BY scCO_2 TO THE SYNTHESIS OF POLYMER/METAL NANOCOMPOSITES

摘要

Polymer swelling by scCO_2 was mainly studied to understand many industrial processes, especially in the field of pharmacy for drug delivery (impregnation) and also polymer processing by CO_2-assisted extrusion. We have studied here another application of polymer swelling by scCO_2 for the synthesis of nanocomposites. The selected model system was the direct synthesis of copper nanoparticles in a poly(ethylene glycol) matrix (PEG). The study of the formation of nanostructures in polymer matrix is constituted of three main steps: ⅰ) thermodynamical behaviour of the polymer/CO_2 system, ⅱ) viscosity of the polymer/CO_2 system and ⅲ) nucleation and growth of copper nanoparticles. First, the thermodynamical behaviour of the PEG/CO_2 system was studied by in situ IR spectroscopy. This method gives accurate values of the polymer swelling by scCO_2 but also of the CO_2 sorption in the polymer. For example, at 40℃-15MPa, the swelling of PEG is equal to 35% for a CO_2 solubility of 23 wt%. Secondly, we have developed an original falling ball viscometer for the determination of PEG viscosity as a function of CO2 density. A good knowledge of the polymer/CO_2 system is finally used for the control of formation of copper nanoparticles. This formation was followed by in situ UV - visible spectroscopy and characterized by transmission electron microscopy.