Effect of Hydrogen Bonding on Dynamic Rheological Behavior of PVA Aqueous Solution

The rheological behavior of polyvinyl alcohol (PVA) aqueous solution is crucial to optimizing the processing technology and performance of PVA products. In this paper, the dynamic rheological behavior of PVA aqueous solution was investigated in detail. PVA solution with a concentration of 10 wt% showed unnormal rheological behaviors, that is, the liquid-like behavior in the high frequency (omega) region and the solid-like behavior in the low omega region. A storage modulus (G ') plateau appears in the relatively low omega region as a gel with a network structure. Different from conventional hydrogel, this plateau has a low modulus, and the corresponding size of the relaxation unit is estimated to be 554 nm, being higher than the size of a whole PVA chain. It is believed that the network mesh is formed by the intermolecular hydrogen bonding interactions among PVA chains. The relaxation time of these meshes is longer than the reptation time of a PVA chain. Based on the relaxation spectrum and calculation analysis, it is found that the destruction of intermolecular hydrogen bonds, such as by heating up, adding sodium dodecyl sulfate, and shear operation, will make the relaxation unit (mesh) larger and lead to the left shift of the intersection of G ' and loss modulus (G ''). In a PVA solution with a high concentration, multiple meshes of various sizes could be formed and thus generate multiple relaxation peaks. The large-sized meshes mainly contribute to the left shift of the intersection of G ' and G '', and the small-sized meshes contribute to the high plateau modulus. The results in this paper offer a new angle to analyze polymer solutions with strong intermolecular interaction.

Automated summary

This paper investigates the dynamic rheological behavior of PVA aqueous solution and discovers the existence of a gel plateau with a network structure in the low frequency region. The gel network is formed by intermolecular hydrogen bonding interactions among PVA chains, and its relaxation time is longer than the reptation time of a PVA chain. Multiple network structures of various sizes can be formed in high concentration PVA solutions, contributing to different rheological properties.