Strong Polymers for Safety Products
Polymers—plastics and rubbers—are widely used commercially and industrially in many safety-critical products, such as tires, helmets, playground equipment, airplanes, and medical devices. Most polymer development to date has focused on improving initial properties of the material—stiffness and strength, for example. Eventually these material properties degrade. Given the diverse and somewhat unpredictable loads that these materials experience over their lifetime, it is incredibly difficult to predict when and where degradation will occur. Currently structures are therefore overdesigned—making some safety products heavier, more expensive, and more wasteful, while still being vulnerable to unpredictable degradation and damage.
With this CAREER award, Meredith Silberstein, Sibley School of Mechanical and Aerospace Engineering, is developing polymers augmented on the molecular scale to react to the onset of damage by strengthening themselves locally. These are referred to as mechanochemically responsive polymers. Such materials would have longer lifespans and in particular are less susceptible to accumulated damage through high intensity short duration loads (such as helmet impact). This material concept will lead to reduced waste, weight of structures, and lower inspection costs for safety-critical applications.
Mechanochemically responsive polymers can be realized through the covalent incorporation of mechanophores—chemical units that undergo a specific chemical transformation in response to applied force. Silberstein and her team are approaching their focus area—elastomers and glassy polymers—through a combined theory, simulation, and experimental technique. The theory and methods developed will lay the groundwork for mechanochemically responsive polymer design.