Comment on "water-driven programable polyurethane shape memory polymer: Demonstration and mechanism" [Appl. Phys. Lett. 86, 114105 (2005)]

Some of the comment of W. M. Huang, B. Yang, L. An, C. Li, and Y. S. Chan on water-driven programmable polyurethane shape memory polymer are discussed. There are two points essentially made by Huang et al. that includes hydrogen bonding is identified as the reason behind water-driven programmable polyurethane SMP and The absorbed water is quantitatively separated into two parts that is the free water and bound water. Liquids added to polymers to make them softer and more flexible at ambient temperature are known as plasticizers. The solution molecule has plasticizing effect on the polymer first, followed by chemical or physical interaction, resulting in transition temperature, being reduced to the ambient temperature. The mechanism of hydrogen bonding increases the flexibility of macromolecular chains virtually. The hydrogen bonding just has an indirect effect on the transition temperature.