Shape Memory Polymer

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Definition

A shape memory polymer, trade name veriflex, that returns to its straight shape upon heating after it is twisted.

A shape memory polymer is a polymer that can be deformed, only to undergo a conformational change back to its original 'memorized' form upon application of some external stimulus, such as temperature (most typically), electricity, magnetism, light, or pH. It occurs by a polymer being able to undergo strain induced phase changes. What this means is that a polymer is set in a form by conventional methods, then when deformed, the microstructure undergoes a phase change. When the stimulus is applied, such as temperature, the phase then transfers back to the original phase, reconforming and relieving the strain in the process.

Applications

Despite SMP technology being developed and understood for quite some time there are currently only a few notable industrial applications. One of which is the grips for robotics. The SMP allows for a soft grip to become firm after it is in contact with the substrate. Other applications are foams that expand and contract to seal window frames during the different seasons, and in sports helmets to provide increased protection and comfort during use.

Future applications

Implants and stents are two biomedical applications that currently use shape memory alloys, thus could be extended to SMPs due to their increased biocompatibility. Also, wound closure devices that could improve scar reduction have also been proposed. Another interesting application is in car parts, in this case a dent in a car, particularly the bumper, could 'pop' itself back into place when heated. Finally, clothes that unwrinkle in the dryer has also been suggested - which would make many peoples lives, including my own, much easier!

References

Lendlein, A., Kelch, S. Shape-memory polymers. Angew. Chem. Int. Ed. Engl. 41, 2034-2057 (2002)

http://www.eng.buffalo.edu/Courses/ce435/Lendlein02.pdf