Multiscale analysis of viscoelastic properties, topography and internal structure of a biodegradable thermo-responsive shape memory polyurethane

In this paper, the effect of the temperature on viscoelastic properties of the thermo-responsive biodegradable shape memory polyurethane (SMPU) is presented. Comprehensive micro and nano mechanical and morphological studies were performed to assess the behavior of the considered material in the form of 3D-printed fibers. For this purpose, specimen's topography, nano-mechanical and macro-mechanical characterization of the material were carried out. Data obtained from the temperature-dependent AFM indentation test was used to quantify nanoscale viscoelastic properties of the investigated material. Power-law rheology (PLR) was chosen as constitutive viscoelastic relaxation model describing behavior of the investigated material at different temperatures. Topography and phase contrast studies done in the nanoscale exposed bi-phasic structure of heated SMPU polymer - soft and hard domains corresponding with structural composition of the material were detected. The applied fitting procedure enabled for the identification of the viscoelastic properties of the revealed phases identified as the hard and the soft domains.