Quantitative separation of the influence of hydrogen bonding of ethanol/water mixture on the shape recovery behavior of polyurethane shape memory polymer

A thermally responsive polyurethane shape memory polymer (SMP) can be actuated in water through a hydrogen bonding interaction between water and the SMP. In this work, we present a comprehensive approach to quantify the hydrogen bonding on the shape recovery behavior of a polyurethane SMP. The stimuli response to the hydrogen bonding of the polyurethane SMP was investigated in ethanol/water mixtures by varying the water content. It was found that depending on the water content, the SMP features a critical hydrogen bonding strength associated with its shape recovery behavior. The Hildebrand solubility parameter theory was employed to quantitatively identify and separate the hydrogen bonding effect of the ethanol/water mixture on the shape recovery ratio and the time. Furthermore, a phenomenological model was developed to predict the glass transition temperature and the shape recovery time of a polyurethane SMP and was verified by the available experimental results.