A wide angle x-ray diffraction (WAXD) study of thermal and chemical actuation of a shape memory polymer

The one way effect of the shape memory polymer ESTANE ETE 75DT3 (abbreviation: SMP-E) can be chemically triggered by exposure to methanol, ethanol, and 1-propanol. The present study uses wide angle x-ray diffraction to confirm that programming induces oriented structure in an initially amorphous state. During subsequent shape recovery the sharp diffraction intensity peaks of the programmed state weaken, and oriented amorphous structure is partly lost. This corresponds to the finding that initial shapes cannot be fully recovered. The present work shows that the uptake of small alcohol molecules not only triggers shape recovery but also weakens intermolecular bonds, which results in strength decreasing. From the alcohol concentrations that were measured by weight gain studies, it can be concluded that the key parameter that governs the mechanical and functional behavior of SMP-E is the number of C-atoms that the SMP-E takes up. It is shown that thermal shape recovery is more effective than chemical shape recovery. Chemically triggered shape recovery can be used to lift small end loads corresponding to stresses of up to 1 MPa. The results are discussed in the light of previous work published in the literature.