Quantitative Predictions of Shape-Memory Effects in Polymers.

Unique shape-memory transitions manifested by directional extension and subsequent retraction in polymers are attributed to stored conformational entropy. This behavior is quantified in terms of stored (ΔS S ) entropic energy density, the maximum strain (εmax ), and stress (σSF at εmax ). This concept allows quantitative assessments of the shape-memory effect (SME) and can be utilized in any material that exhibits a glass-transition temperature (T g ) and a rubbery plateau.