Programmable shape memory bismaleimide composite claw with two-way grabbing function

Abstract

• A series of shape memory polymers (SMPs) based on bismaleimide (BMI) were synthesized. The BMI-based polymers are made of a 4,4'-bismaleimidodiphenylmethane (BDM) matrix and chain extender polyether diamine poly(propyleneglycol) bis(2-aminopropylether) (D400). Then crosslinking agent 2,4-tolylene diisocyanate (TDI) was added to form a crosslinking network. Last, it was toughened by adding liquid nitrile rubber (ETBN). • These BMI-based SMPs achieved wide T g ranges of 170-200 °C. This property allows these SMPs to remember two pre-deformed shapes. By designing the second pre-deformed shape similar to the original shape, the 2W-SME can be achieved. • Carbon fabric reinforced BMI-based shape memory composites (SMPCs) were prepared. By exploring the preparation process, the claw structure was formed with this BMI-based SMPC. The composite claw realizes the motion of reach out and grab 250g items. Functional polymer materials with a two-way shape memory effect (2W-SME) have attracted great interest recently. Herein, by introducing 2,4-tolylene diisocyanate (TDI) into the bismaleimide (BMI) network, the shape memory polymers we synthesized are a series thermosetting polymers with adjustable T g and triple-shape memory effect(triple-SME), and realized two-way behavior by programming. Those shape memory polymers (SMPs) were toughened by acrylonitrile-butadienerubber (ETBN) and reinforced with carbon fabric to make composites. The cured network with varying transition temperatures and flexibility was synthesized by varying the cyanate ester and rubber concentration in the system. Polymers with a broad glass transition temperature ( T g ) range can achieve triple-SME. Due to the complex cross-linked structure, the two-way behavior demonstrated above for BMI-based SMPs stem from its broad T g ranges. Select two temperatures higher and lower than T g as the switching temperature, and fix the pre-deformed shape in the opposite direction at these two temperatures to achieve the two-way behavior. These BMI-based SMPs could grab objects through the design of the structure. Results indicated that the above BMI-based SMPs with two-way function have excellent thermal stability and mechanical properties, which provides the basic attempts for the further development of thermosetting SMPs and their composite materials.