Effect of Solvent Characteristics on the Ultrasonic Degradation of Poly(vinylpyrrolidone) Studied by On‐line Monitoring

Abstract

Ultrasonic degradation of high molecular weight poly(vinylpyrrolidone) is monitored on‐line, by light scattering. Degradations are performed in water/methanol mixtures of various compositions at room temperature. The evolutions of the weight average molecular weight and the radius of gyration are monitored. The dependence of the radius of gyration on the molecular weight is found. The second virial coefficients (A2) of polymer samples in each solvent are found using Zimm plots. These mixtures are found to be close to theta solvents for poly(vinylpyrrolidone). Degradation rate constants and limit molecular weights are correlated with the radii of gyration and A2 coefficients of the polymer in the solvents studied. It is found that degradation is more effective in better solvents.The dependence of the degradation parameters on solvent characteristics (e.g., the enthalpy of vaporization, solvent viscosity and surface tension) was also investigated and found to be much less significant than for the parameters above.magnified image

Ultrasonic degradation of polyvinyl pyrrolidone in mixed water/acetone

“…(5) and the value of parameters α and β in eq. (5) were obtained 1 and 0.6, respectively, the obtained order reaction is consistent with the results of Giz et al15 and Madras et al14 Nevertheless Taghizadeh et al13 reported various order of reaction for various molecular weights. The authors believed that the order of reaction can not be dependent to the molecular weight.…”

“…Giz and coworkers are suggested that the average molecular weight evolution could be approximated as14 where β is a measure of the heterogeneity of the process and left as a fit parameter. This model is fitted to experimental data and the best value of β is found to be 1/3.…”

“…Taghizadeh et al are investigated the effect of molecular weight on the ultrasonic degradation of PVP in water and chloroform 12, 13. Aarthi et al are studied the degradation of PVP under ultrasonic, ultraviolet radiation, and combined ultrasonic and ultraviolet 14. Akyuz et al are studied the ultrasonic degradation of PVP in mixtures of water/methanol 15.…”

Photo-Assisted Sondegradation of Hydrogels in the Presence of TiO2Nanoparticles

“…[50][51][52] Moore et al approved this idea by an isotope labeling experiment on ultrasonic degradation of linear PEG. They demonstrated that when a single weak azo link was positioned at the center of a linear PEG chain, mechanically-induced cleavage was localized almost exclusively to the single weak site.…”

A kinetic study of ultrasonic degradation of carboxymethyl cellulose

“…40,41 In general, polymer mechanochemistry induced by an acoustic field is a nonrandom process; for example, the scission of polymer chains in solution occurs at a preferential position near the midpoint. [42][43][44] Moore et al approved this idea by an isotope labeling experiment on ultrasonic degradation of linear polyethylene glycol (PEG). They demonstrated that when a single weak azo link was positioned at the center of a linear PEG chain, mechanically induced cleavage was localized almost exclusively to the single weak site.…”