Effect of Intramolecular Hydrogen Bonds on the Single-Chain Elasticity of Poly(vinyl alcohol): Evidencing the Synergistic Enhancement Effect at the Single-Molecule Level

Poly(vinyl alcohol) (PVA) can form intramolecular and intermolecular hydrogen bonds (H-bonds) within themselves or with others. These H-bonds exhibit remarkable influence on the nature of PVA, but the details about their respective effects are still unclear. Herein, the effect of intramolecular H-bonds on the single-chain elasticity of PVA has been studied by single-molecule atomic force microscopy (AFM) in the absence of intermolecular H-bonds. The average energy of intramolecular H-bonds has a positive correlation with the degree of alcoholysis (DA) of PVA, suggesting that there is a synergistic enhancement effect between the intramolecular H-bonds. Moreover, the higher the DA, the stronger the synergistic effect. Such a strong synergistic effect on PVA with a high DA may be the key factor to its low water solubility at room temperature. It is expected that this study will lay the foundation for future research on the influence of intermolecular H-bonds on the properties of PVA.