Phase transitions of polymers over T and P ranges under various hydraulic fluids: Polymer/supercritical gas systems and liquid to solid polymer transitions

International audience; Recently obtained results on gas-polymer interactions and associated molecular organizations are reported. As a matter of fact, they are of interest for several applications from petroleum industry to nano-science and polymer processing. They constitute an incursion into the thermodynamics and kinetics of solid polymer/gas interactions and liquid polymer/gas interactions as well as solid to liquid (polymer) transitions. Experimental and theoretical studies have been conducted to better understand the competition between the effects of solubility/plasticization and of hydrostatic pressure of a gas in the polymer-rich phase and also the importance of the interface in block copolymers. A relation characterizing the global isobaric thermal expansion of thermoplastic semi-crystalline polymers saturated in gas has been developed. In addition, it has been shown that the control of the supercritical conditions of the gas enabled to successfully monitor the size of nano-structures appearing by self-assembling in di-block copolymers. The overall kinetics of the liquid to solid transition, that is crystallization, of a semi-crystalline polymer has been described within the framework of Avrami general assumptions. A system of differential equations has been derived for quiescent crystallization and extended to flow-induced crystallization which can be used to predict the formation of microstructures.