Abstract
In the present work, we study the role of programming strain (50% and 100%), end loads (0, 0.5, 1.0, and 1.5 MPa), and chemical environments (acetone, ethanol, and water) on the exploitable stroke of linear shape memory polymer (SMP) actuators made from ESTANE ETE 75DT3 (SMP-E). Dynamic mechanical thermal analysis (DMTA) shows how the uptake of solvents results in a decrease in the glass temperature of the molecular switch component of SMP-E. A novel in situ technique allows studying chemically triggered shape recovery as a function of time. It is found that the velocity of actuation decreases in the order acetone > ethanol > water, while the exploitable strokes show the inverse tendency and increases in the order water > ethanol > acetone. The results are interpreted on the basis of the underlying chemical (how solvents affect thermophysical properties) and micromechanical processes (the phenomenological spring dashpot model of Lethersich type rationalizes the behavior). The study provides initial data which can be used for micromechanical modeling of chemically triggered actuation of SMPs. The results are discussed in the light of underlying chemical and mechanical elementary processes, and areas in need of further work are highlighted.
Highlights
Shape memory polymers (SMPs) are stimulus-responsive materials which show shape recovery
Two data points for as-processed shape memory polymer (SMP)-E are included, one which was reported by Mogharebi et al [37] and the result presented in Figure 4 for the as-processed material studied in the present work
Results obtained for SMP-E programmed to a programming strain of 100% during exposure to acetone, ethanol, and water are shown in Figure 11, where the same types of plots were used as in Figures 7 and 10
Summary
Shape memory polymers (SMPs) are stimulus-responsive materials which show shape recovery. There are excellent reviews which cover this fascinating class of materials (e.g., [1,2,3,4,5,6,7,8,9]). SMPs receive special attention in the biomedical field [1,2,8,9,10,11,12,13,14]. A few articles discussed potential applications in aerospace technology [15,16]. Sensor applications have been considered [17]. Fundamental studies have focused on the interaction of shape recovery and swelling [18] and on effects associated with thermal cycling [19]
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