Light-induced SMPs
Light-activated shape-memory polymers (LASMP) use processes of photo-crosslinking and photo-cleaving to change Tg. Photo-crosslinking is achieved by using one wavelength of light, while a second wavelength of light reversibly cleaves the photo-crosslinked bonds. The effect achieved is that the material may be reversibly switched between an elastomer and a rigid polymer. Light does not change the temperature, only the cross-linking density within the material. For example, it has been reported that polymers containing cinnamic groups can be fixed into predetermined shapes by UV light illumination (> 260 nm) and then recover their original shape when exposed to UV light of a different wavelength (< 260 nm). Examples of photoresponsive switches include cinnamic acid and cinnamylidene acetic acid.
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