Studies on the Hydration Behavior of Polyvinyl Alcohol in Aqueous Solution: A Kinetic Approach through the Hydrolysis of Benzocaine

Abstract

The present work investigates the structural and dynamical features of Polyvinyl alcohol (PVA) and surfactant–PVA system through the change in the rate of hydrolysis of benzocaine. The UV–Vis spectra of benzocaine showed that the absorbance values at λmax (284 nm) increased with the increase in PVA. The rate of hydrolysis decreased in the dilute‐ and high‐concentration regions of PVA, whereas it remains unchanged in the mid‐concentration range of PVA, known as the polymer–polymer interaction region. These observations correspond to the structural changes in PVA with the increase in PVA concentration in aqueous solution. The aggregation behavior of PVA was further studied using transmission electron microscopy micrographs. The rate constant for the hydrolysis of benzocaine showed peaked behavior with the increase in [CTABr] in the CTABr‐PVA mixed system. The sodium dodecyl sulphate (SDS) molecules modify the PVA chains into a more compact form, and so, the hydration number around PVA is decreased. Consequently, the less hydrophilic benzocaine entangles with SDS‐PVA, whereas OH– ions aggregate into the aqueous pseudophase, resulting in a decrease in the rate of hydrolysis in the SDS–PVA mixed medium. The calculated value of binding constant increased with the increase in PVA in both CTABr‐PVA and SDS‐PVA mixed systems.

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“…PVA is a water-soluble, biodegradable synthetic biopolymer. PVAs are categorized into different grades based on the degree of hydrolysis (the ratio of hydroxyl to acetyl groups) and the degree of polymerization, both of which affect water solubility (Kaiwen et al 2016 ; Rahman et al 2020 ). The physicochemical characteristics of PVA, such as hydration, dielectric constant, conformation, and dynamics, are affected by interactions between water molecules and the –OH group of PVA in their aqueous solution.…”

“…Since PVA contains both hydrophilic and hydrophobic groups, it will form a micelle-like structure and provide ideal conditions for the solubilization of weakly aqueous soluble curcumin. The formation of multiple stranded micelle-like structures contributes to changes in physical properties (Rahman et al 2020 ). The rheological properties and adsorption characteristics at solid–liquid interfaces of these solutions vary from the aqueous medium.…”