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	{{Material-science-stub}}		{{Material-science-stub}}
			== Shape-memory polymer gallery ==
			<gallery>
			File:wiki thermomechanical test.jpg\|Thermomechanical test
			File:SMProcess.jpg\|Shape-memory process
			File:wiki norbornene.jpg\|Norbornene
			File:lightinduced.jpg\|Light-induced shape-memory effect
			</gallery>

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'''Shape-memory polymers''' (SMPs) are a class of [[polymer]]s that have the ability to return from a deformed state (temporary shape) to their original (permanent) shape induced by an external stimulus (trigger), such as temperature change. SMPs are finding applications in various fields such as [[biomedical engineering]], [[aerospace engineering]], and [[textile engineering]] due to their unique properties and functionalities.

==Overview==
Shape-memory polymers are characterized by their ability to undergo a physical change when exposed to a specific external stimulus. Unlike [[shape-memory alloys]], which are well-known for their use in medical stents and eyeglass frames, SMPs offer advantages such as easy processing, lower cost, and higher capacity for deformation. The shape-memory effect in polymers is primarily due to the presence of two distinct phases: a fixed phase that determines the permanent shape and a reversible phase that allows the material to be deformed and fixed into a temporary shape.

==Mechanism==
The shape-memory effect in SMPs involves two main processes: programming and recovery. During programming, the polymer is heated above its transition temperature (T_trans), which is either the [[glass transition temperature]] (T_g) or the melting temperature (T_m), allowing it to be easily deformed. The material is then cooled under constraint to below T_trans, fixing the temporary shape. Upon reheating above T_trans, the stored mechanical energy is released, and the polymer returns to its original shape.

==Types of Stimuli==
While temperature is the most common stimulus for SMPs, other stimuli such as light ([[photo-induced]] shape memory), electric field ([[electroactive polymers]]), magnetic field ([[magnetoactive polymers]]), and solution ([[chemo-responsive polymers]]) have also been explored. This versatility opens up a wide range of applications for SMPs.

==Applications==
===Biomedical===
In the biomedical field, SMPs are used in [[drug delivery systems]], [[sutures]], [[stents]], and [[tissue engineering]]. Their ability to change shape at body temperature or in response to other stimuli makes them ideal for minimally invasive surgical procedures and targeted therapies.

===Aerospace===
In aerospace, SMPs contribute to the development of [[morphing wings]] and self-healing structures. Their light weight and adaptive characteristics offer significant advantages in terms of fuel efficiency and maintenance.

===Textile===
In textile engineering, SMPs are used to create [[smart fabrics]] that can adapt to environmental changes or provide comfort and protection to the wearer by changing their porosity or rigidity.

==Challenges and Future Directions==
Despite their potential, the widespread adoption of SMPs faces challenges such as the need for improved material properties (e.g., strength, durability) and better understanding of their long-term behavior. Ongoing research is focused on developing new SMPs with enhanced functionalities and on expanding their applications through innovative engineering solutions.

==See Also==
* [[Polymer]]
* [[Smart material]]
* [[Biocompatibility]]
* [[Nanotechnology in medicine]]

[[Category:Polymers]]
[[Category:Smart materials]]
[[Category:Materials science]]

{{Material-science-stub}}

Shape-memory polymer - Revision history

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