The Study of Ultrasonic Degradation of Superabsorbent Hydrogels

Viscometry is a valid and practical approach for monitoring the degradation of polymers in solution. In this work, at constant power and pulse, the effects of different operating parameters such as time of irradiation, temperature, solution concentration, volume, solvent, and immersion depth of horn on the rate of degradation have been investigated in aqueous solution using laboratory scale operation. A method of viscometry was used to study the degradation behavior of aqueous dispersions of microgels. The experimental results show that the viscosity of polymer solution decreased with an increase in the ultrasonic irradiation time and approached a limiting value. The present work has enabled us to understand the role of the different operating parameters in deciding the extent of viscosity reduction in aqueous dispersions of microgels and also the controlling effects of them. 1. Introduction Hydrogels, both natural and synthetic, are used in a myriad of applications, particularly as medical devices, including therapeutic contact lenses, wound dressings, injectable drug-delivery vehicles, and tissue-regeneration scaffolds. Biomaterials need to be removed from the body once they complete their roles in the body, and degradable materials could be ideal for this purpose [1–5]. In addition, drug molecules may be covalently bound to nondegradable polymer networks with a degradable linkage. As such, the rate of release for these gels is dependent on the cleavage kinetics of the drug-network linkage. Shortening of the polymer chains can be achieved by various methods such as thermal, photo, and catalytic degradation [6–8]. The methods like UV [9–13], gamma radiation [13, 14], and microwave [14, 15] are also important. Ultrasound, photo, and chemical methods require less energy for polymer degradation. Further, interaction between them and the polymeric systems can help find the degradation pathways or mechanisms [8–10, 16–18]. Many scientists have investigated the ultrasound degradation of polymers [7, 10, 12–14]. The effects of various parameters like ultrasound pulse and intensity [12, 17–20], frequency [20, 21], temperature [17, 22–24], vapor pressure, volume [19, 23, 24], solvent [17, 22], dissolved gases [21], molecular weight [25, 26], and polymer concentration [12, 19, 20] on the ultrasonic degradation of macromolecules have been studied. The ultrasonic degradation of low density polyethylene at different concentrations, volumes, and temperatures has been studied. The results showed that the extent of degradation decreased with an increase in reaction