3D Printable Soft Elastomers

Existing feedstock for 3D printing is nearly all plastics. These materials are not only mechanically stiff but also fragile. These severely limit their applications where soft, elastic polymers are required to easily comply with the shapes of objects they contact. Here we develop a soft, 3D printable elastomer through molecular design. We synthesize a triblock copolymer, in which the two end-blocks are polystyrene (PS) with a high glass transition temperature, T_g, about 100^oC, and the middle block is a polydimethylsiloxane (PDMS) with a low T_g, about 100^oC. At room temperature, such copolymers self-assemble to a network, in which the effective network strands are the PDMS, and crosslinks are glassy plastic domains formed by PS. This network is extremely soft with Young's modulus below 100kPa, more than three orders of magnitude lower than that of plastics. At high temperature, the glassy domains dissociate, enabling a temperature triggered solid-to-liquid transition. Harnessing this feature, we use extrusion-based 3D printing to create a complex, hierarchical 3D structure with an exceptional combination of softness and deformability. Our studies provide a new strategy for the development of 3D printable soft elastomers.