Self-adaptive water vapor permeability and its hydrogen bonding switches of bio-inspired polymer thin films

Developing materials with self-adaptive water vapor permeability is fueled with industrial demands. Polymers have enabled such a behavior with thermal-responsive water vapor permeability reported in the literature, but little work is reported on the moisture-sensitive water vapor permeability which is even more important for many applications, such as clothing comfort, since sweating can be enormous when actively exercising in the cold. In this paper, a polymer inspired by a leaf guard-cell and designed by introducing supramolecular hydrogen-bonding switches and moisture-sensitive self-adaptive water vapor permeability has been achieved. It is suggested that hydrogen bonding can become a moisture-responsive switch when its bonding energy is smaller than the energy between the water molecule and the switch itself, but much bigger than that of water.