Shape memory polymers heat-triggered

To date, heat-triggered shape memory polymers have had the greatest share of research and application adaptation. However, trigger mechanisms could also be chemo-responsive, e.g., water, ethanol, and pH change photo-responsive, e.g., UV or IR, including radio waves and/or mechano-responsive, e.g., stretching, impact, etc. 

An ideal shape-memory polymer for a given application has a small set of parameters that determine the usefulness, or otherwise, for a given application (1) The fractional recoverable strain the maximum fraction of the imposed strain that can be recovered when triggered. (2) The temperature of maximum recovery rate Tmax for a given rate of heating a measure of the temperature required to trigger... 

The most studied SMPs are thermally activated. This means that the shape recovery is triggered by heating the polymer to a temperature above its switching temperature. Marty researchers have achieved the SME on conventionally thermally-active SMPs. Employing hydrophilic or water solirble ingredients in SMPs can accelerate the moisture/water-active shape recovery process. Chen et al. (2007a) developed a water-active shape memory biodegradable polymer from chitosan cross-linked with epoxy. The chitosan is relatively hydrophilic. 

Shape recovery in a particular SMP may be triggered by a few different stimuli. For instance, heat, water, and ethanol are all possible stimuli for polyurethanes and their composites. Additional advantages of SMPs over their metallic counterparts include high recoverable strain and easily tunable properties (http //www.azom.com/article. aspx ArticleID=6038, 13—15). Furthermore, scientific studies have also revealed that almost all polymers intrinsically have shape memory effect (SME) properties, which are also thermo- and chemo-responsive, i.e., the SME in most polymers can be either thermally activated or chemically triggered. 

---