Solubility study of polyacrylamide in polar solvents

Contact angles and surface tension data were measured to obtain the surface tension components of polyacrylamide (PAM). According to Van Oss, Chaudhury, and Good (VCG) theory, the surface tension components were used to calculate the PAM solubility in five different polar solvents: water, ethylene glycol (EG), acetone, ethanol, and dimethyl formamide (DMF). It was found that PAM had a monopolar surface nature, which resulted in polymer dissolution in water. The solubility of PAM in water was greater than in EG, but PAM was solvophobic in the other three solvents. For PAM, water, and the second solvent (cosolvent) ternary system, the solubility of PAM could not be calculated directly. Surface tension was used as an index of polarity for cosolvent systems (the mixture of water and the second solvent). The cosolvent polarity decreased when the composition of the second solvent increased. PAM would be dissolved in the cosolvent when the system's polar contribution was greater than the apolar contribution. The apparent surface tension of PAM aqueous solutions was not sensitive enough to show polymer conformation changes when additive concentrations were changed. The solubility of PAM in binary polar solvent systems or ternary cosolvent systems was used to estimating the swelling properties of a PAM hydrogel under corresponding external conditions. (C) 2004 Wiley Periodicals, Inc.