Ultrasonic degradation of poly(acrylic acid)

Abstract

The ultrasonic degradation of poly(acrylic acid), a water-soluble polymer, was studied in the presence of persulfates at different temperatures in binary solvent mixtures of methanol and water. The degraded samples were analyzed by gel permeation chromatography for the time evolution of the molecular weight distributions. A continuous distribution kinetics model based on midpoint chain scission was developed, and the degradation rate coefficients were determined. The decline in the rate of degradation of poly(acrylic acid) with increasing temperature and with an increment in the methanol content in the binary solvent mixture of methanol and water was attributed to the increased vapor pressure of the solutions. The experimental data showed an augmentation of the degradation rate of the polymer with increasing oxidizing agent (persulfate) concentrations. Different concentrations of three persulfates-potassium persulfate, ammonium persulfate, and sodium persulfate-were used. It was found that the ratio of the polymer degradation rate coefficient to the dissociation rate constant of the persulfate was constant. This implies that the ultrasonic degradation rate of poly(acrylic acid) can be determined a priori in the presence of any initiator.

Photo, thermal, and ultrasonic degradation of EGDMA‐crosslinked poly(acrylic acid‐co‐sodium acrylate‐co‐acrylamide) superabsorbents

“…k US (μ) is assumed to be a linear function of viscosity, that is, $ {\rm{k}}_{{\rm{US}}} {\rm{(\mu ) = \kappa }}_{{\rm{US}}} {\rm{ (\mu - \mu }}_{{\rm{lim}}} {\rm{)}} $ . Similar dependence of the ultrasonic degradation rate coefficient on the MW has been previously reported 30, 31. The higher molecular weight species undergo degradation at a faster rate than those of lower molecular weights, and no degradation occurs below a limiting molecular weight 30.…”

“…Similar dependence of the ultrasonic degradation rate coefficient on the MW has been previously reported. 30,31 The higher molecular weight species undergo degradation at a faster rate than those of lower molecular weights, and no degradation occurs below a limiting molecular weight. 30 This relationship ensures that the rate coefficient becomes zero when viscosity reaches the limiting viscosity (l lim ) and no further degradation of the gel takes place.…”

“…The ultrasonic degradation of the polymers is interesting because of its distinctive characteristics such as preferential scission at the mid‐point of the chain,29 higher rates of degradation of the higher molecular weight species, and existence of a limiting molecular weight below which degradation does not occur 30. The ultrasonic degradation of the water‐soluble polymers such as poly(ethylene oxide),30 poly(acrylamide),30 and poly(acrylic acid)31 has been widely studied; however, there are no reports of the degradation of AA‐based crosslinked SAPs.…”

Kinetics of adsorption of methylene blue and rhodamine 6G on acrylic acid‐based superabsorbents

“…The understanding of the adsorption characteristics of the equilibrium swollen SAPs is important, as the SAPs from the domestic waste in contact with textile effluents may be either in dry or in equilibrium swollen state. In our previous study,26 the adsorption of four cationic dyes Acriflavine, Auramine‐O, Azure‐I, and Pyronin‐Y on dry ethylene glycol dimethacrylate (EGDMA) crosslinked poly(acrylic acid‐ co ‐sodium acrylate‐ co ‐acrylamide) superabsorbents was investigated. In this study, we investigate the adsorption of different dyes (MB and rhodamine 6G) on both the dry and swollen polymer.…”

The Study of Ultrasonic Degradation of Superabsorbent Hydrogels

“…Shortening of the polymer chains can be achieved by various methods such as thermal, photo, and catalytic degradation [6][7][8]. The methods like UV [9][10][11][12][13], gamma radiation [13,14], and microwave [14,15] are also important. Ultrasound, photo, and chemical methods require less energy for polymer degradation.…”