Triple-shape polymeric composites (TSPCs)

In this paper, the fabrication and characterization of triple-shape polymeric composites (TSPCs) that, unlike traditional shape memory polymers (SMPs), are capable of fixing two temporary shapes and recovering sequentially from the first temporary shape (shape 1) to the second temporary shape (shape 2), and eventually to the permanent shape (shape 3) upon heating, are reported. This is technically achieved by incorporating non-woven thermoplastic fibers (average diameter -760 nm) of a low-T_m semicrystalline polymer into a T_g-based SMP matrix. The resulting composites display two well-separated transitions, one from the glass transition of the matrix and the other from the melting of the fibers, which are subsequently used for the fixing/recovery of two temporary shapes. Three thermomechanical programming processes with different shape fixing protocols are proposed and explored. The intrinsic versatility of this composite approach enables an unprecedented large degree of design flexibility for functional triple-shape polymers and systems.