Self-aligned and hierarchically porous graphene-polyurethane foams for acoustic wave absorption

Manipulating the morphology of three-dimensional (3D) cellular structures in both macroscale and microscale is very important in designing a sound absorbing material effective in a broad frequency bandwidth. However, it is extremely difficult to synthesize the hierarchical porous structures having nano- and micro-pores in a self-assembled or controlled manner. Herein, we report an efficient strategy to fabricate the self-aligned and hierarchically porous graphene-polyurethane foams as a sound absorbing material via electrostatic repulsion mechanism of graphene oxide and potassium hydroxide activation. Two unique microscopic cellular structures are designed by controlling the morphology of graphene layers inside the polyurethane backbone using spontaneous self-alignment and stochastic disruptive methods, respectively. The obtained heterogeneous graphene microstructure network provides enhanced mechanically load-bearing ability and significantly improves the sound energy attenuation performance over 312% compared to pristine sound absorber depending on the existence of ordered or disordered graphene lattices, resulting in an efficient pathway for rapidly decaying out acoustic wave energy.