Understanding the\nEffect of Water Absorption on the\nMicrostructure, Molecular Kinematics, and Relaxation Behavior of Polyvinyl\nButyral Films

The effects of water molecules on the chemical structure,\nmicrostructure,\nmolecular kinematics, and relaxation behavior of polyvinyl butyral\n(PVB) films were investigated. The 2D ATR-FTIR results demonstrated\nthat water molecules initially interacted with free O–H and\nCO, subsequently with hydrogen-bonded O–H and CO\nbetween the hard and soft segments, and ultimately with hydrogen-bonded\nO–H and CO in the hard segments. The SEM, AFM, DSC,\nand SAXS-WAXS results indicated that the microphase separation structure\nof PVB was formed by soft and hard domains, and the entry of water\nmolecules disrupted the original structural regularity of the hard\nsegments of the PVB films, resulting in a decrease in microphase separation\ndegree. The BDRS results showed that water absorption had a significant\neffect on the molecular kinematics of the soft segments and the hard–soft\ninterface. The results of the stress relaxation behavior showed that\nthe relaxation properties of PVB films deteriorated after water absorption.