Qualitative separation of the physical swelling effect on the recovery behavior of shape memory polymer

The physical swelling effect-induced shape recovery is studied in a thermo-responsive styrene-based shape memory polymer (SMP). Fourier transform-infrared (FTIR) test reveals no apparent change in the characteristic polar bonds of CO and O–H after immersing the SMP into toluene solvent. Based on the rubber elastic and relaxation theory, the decrease in internal energy is identified as the driving force for the shape recovery. Subsequently, the rubber elastic theory is further applied to investigate the swelling-induced free/constraint shape recovery in this SMP, and the free-energy function is utilized to analyze the swelling-induced homogenous/inhomogeneous deformation. This study provides a framework to study both the swelling effect-induced shape recovery and complex shape memory behavior in solvent-responsive SMPs.

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