Recyclable Oil-Absorption Foams via Secondary Phase Separation

The fabrication of micro- and nanostructures in polymers has attracted considerable attention. Here, a general method defined as secondary phase separation (SPS) is developed, which regulates the growth of polymers into multiple dimensions including one-dimensional (fiber-like), two-dimensional (flower-like), or three-dimensional (3D; sphere-like) structures. A theoretical understanding of the growth evolution in the polymer multidimensional structures is clearly proposed based on classical nucleation theory and Oswalt ripening. In particular, the multidimensional superstructures of poly(lactic acid) (PLA) exhibit strong water repellency (e.g., contact angle > 150°, sliding angle < 10°, and adhesive force < 5 μN). The resultant PLA foam composed of microspheres exhibits good shape recovery after compression due to its 3D alternating rigid (PLA microspheres) and soft (air space) skeleton. This skeleton can be further implemented for the selective absorption of organic pollutants (like chlorobenzene), showing a high yield of up to 21 g g –1 without any mass loss after 10 cycles. This work provides a new strategy to prepare polymer foams with multidimensional micro/nanostructures and shows potential in selective absorption and water purification.