Student Summer Scholars


Study of Polymer Nanocomposites at Cryogenic Temperatures


Positrons, glass transition, cryogenic



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In this experiment, we propose to study the porosity, the empty space between the chemical chains, of polymer samples. Polymers can be engineered to adopt different qualities like increased flexibility or strength. By infusing nanoparticles into the silicone samples we can modify the porosity and structure of the polymer. We are interested in investigating their glass transition temperature (Tg) to see how the porosity changes as we transition from the rubbery to glassy phase. Using Positron Annihilation Lifetime Spectroscopy (PALS) we can determine the porosity of our samples. By analyzing the lifetime of the positronium we can study how the polymer evolves under different conditions. Silicone rubber samples have a Tg below room temperature; therefore, we must cool them. Using a custom built bacuum chamber and an Air Products Displex cryopump we can, potentially, control temperatures down to 70K. With the cold chamber we can study all sorts of materials at cryogenic temperatures using PALS.