Microstructural evolution of polyurea under hydrostatic pressure

Polyurea (PU) is a versatile high strain rate elastomeric polymer that has attracted significant interest due to its utility as blast and ballistic resistant coating. Predictive design of PU materials, particularly with focus on structure, complicated by the occurrence both pressure effects in response impact. To help elucidate behavior under such conditions, we sought characterize microstructural evolution hydrostatic compression. this end, utilized diamond anvil cell in-situ X-ray scattering monitor compression-induced changes two materials differing their soft segment length. We found regardless length, initially phase separated structure becomes increasingly mixed during compression up ~1 GPa. Despite increase mixing, interchain network between urea linkages formed through hydrogen bonds remains apparent at pressures well above 1 The mean spacing associated hydrogen-bonded within hard domains contracts some cases recovers upon load removal. Furthermore, extent deformation recovery depends degree microphase separation dictated length segment, wherein longer deforms less more.