ABSTRACT
Optimization of post polymerization processes of polyolefin elastomers (POE) involving solvents is of considerable industrial interest. To this aim, experimental determination and theoretical interpretation of the thermodynamics and mass transport properties of POE-solvent mixtures is relevant. Sorption behavior of n-hexane vapor in a commercial propylene-ethylene elastomer (V8880 VistamaxxTM from ExxonMobil, Machelen, Belgium) is addressed here, determining experimentally the sorption isotherms at temperatures ranging from 115 to 140 °C and pressure values of n-hexane vapor up to 1 atm. Sorption isotherms have been interpreted using a Non Random Lattice Fluid (NRLF) Equation of State model retrieving, from data fitting, the value of the binary interaction parameter for the n-hexane/V8880 system. Both the cases of temperature-independent and of temperature-dependent binary interaction parameter have been considered. Sorption kinetics was also investigated at different pressures and has been interpreted using a Fick's model determining values of the mutual diffusivity as a function of temperature and of n-hexane/V8880 mixture composition. From these values, n-hexane intra-diffusion coefficient has been calculated interpreting its dependence on mixture concentration and temperature by a semi-empiric model based on free volume arguments.
ABSTRACT
Enabling mechanical responsiveness in field-effect transistors (FETs) offers new technological opportunity beyond the reach of existing platforms. Here a new force-sensing concept is proposed by controlling the wettability of a semiconductor surface, referring to the interfacial field-effect transistors (IFETs). An IFET made by superhydrophobic semiconductor nanowires (NWs) sandwiched between a layer of 2D electron gas (2DEG) and a conductive Cassie-Baxter (CB) sessile droplet is designed. Following the hydrostatic deformation of the CB droplet upon mechanical stress, an extremely small elastic modulus of 820 pascals vertical to the substrate plane, or ≈100 times softer than Ecoflex rubbers, enabling an excellent stress detection limit down to <10 pascals and a stress sensitivity of 36 kPa-1 is proposed. The IFET exhibits an on/off current ratio exceeding 3 × 104 , as the carrier density profile at the NW/2DEG interface is modulated by a partially penetrated electrostatic field. This study demonstrates a versatile platform that bridges multiple macroscopic interfacial phenomena with nanoelectronic responses.
