Influence of Terpolymer Structure on the Performance of Smart Deformable Polyimides

Combining the shape memory effect with photodeformation allows materials to have the ability to be shaped into different forms on demand and to deform under light, expanding the multifunctionality of the materials. However, achieving non-interfering photodeformation and shape memory properties in a single material remains challenging. In this study, we prepared cross-linked azobenzene polyimide using a terpolymerization strategy. The cross-linked structure of the polyimide provided a thermal shape memory effect, allowing it to be programmed into a temporary shape and return to its original shape upon exposure to heat. The azobenzene (Azo) groups in the side chains were employed to achieve reversible photodeformability. To optimize performance, we introduced a second diamine monomer, 4,4'-(1,3-propanedioxy)dianiline (DA3 MG), to fine-tune the azobenzene content in the polymer. The ternary copolyimide exhibits high mechanical strength and excellent thermal stability. When the molar fraction of Azo in diamine monomer is 50%, the balance between light penetration depth and material modulus leads to significant bending angles upon light exposure. Finally, we successfully demonstrated the combination of shape memory and photodeformation properties of the terpolymer. The shape memory effect was used to program the shape of polymer film, giving the photo-responsive material different deformable structures. By applying light, the film was driven to undergo deformation, enabling the execution of actuation. After the actuation was completed, heat was applied to make the film return to its permanent shape. Programming the material's shape using the shape memory effect enables the photo-responsive polymer to have different deformable structures, while the reversible photodeformation allows for actuation, thus providing excellent shape manipulation capabilities.