Active Biomaterials

Shape-memory polymers are stimuli-responsive materials. Upon exposure to an external stimulus, they can change their shape in a predefined way by memorizing a permanent shape. The shape-memory effect is obtained by a combination of the polymer's molecular architecture / morphology with a certain processing and programming technology [1].

In addition such plastics can be designed to be biocompatible and biodegradable resulting in multifunctional materials. Especially biodegradable shape-memory polymers have a high potential for medical applications such as minimally invasive surgery [2, 3, 4].

A bulky implant could be inserted through a small incision into the body in compressed (temporary) shape, where it recovers its pre-programmed, application relevant shape. After a pre-determined time period, the implant will degrade, avoiding second surgery for explantation [5, 6].

Two biodegradable shape-memory polymer systems are presented as examples: A binary blend system with switching temperature around body temperature [7] and biodegradable multiblock copolymers based on oligodepsipeptides [8].

Finally triple-shape materials are introduced, which perform two subsequent shape changes [9, 10].

References

[1] A. Lendlein, R. Langer, Science, 296, 2002, 1673-1676

[2] A. Lendlein, S. Kelch, Angew. Chem. Int. Ed., 41, 2002, 2034-2057.

[3] A. Lendlein, S. Kelch, Shape-Memory Polymers, Encyclopedia of Polymer Science and

Technology, 3rd Edition, John Wiley & Sons, Volume 4, 2002, 125-136.

[4] M. Behl, A. Lendlein, Soft Matter, 3 (1), 2007, 58-67.

[5] A. Lendlein, S. Kelch, Shape-memory polymers as stimuli-sensitive implant materials, Clin. Hemorheol. Microcirc., 32 (2), 2005, 105-116.