Understanding the Mechanisms Involved in Shape Memory Starch: Macromolecular Orientation, Stress Recovery and Molecular Mobility

The effect of a deformation near and above the glass transition on macromolecular orientation, residual stress, and molecular mobility was investigated on amorphous stimuli-responsive starch. The recovery stress, linked to the residual stress in the temporary shape, evolves linearly with the macromolecular orientation. Increasing the deformation temperature decreases the residual stress and the macromolecular orientation. This also leads to a higher glass transition temperature induced by a decrease in molecular mobility. The local structures potentially involved in orientation and stress recovery and their behavior during deformation at different temperatures are discussed.