Effects of swelling on the viscoelastic properties of polyester films made from glycerol and glutaric acid

Viscoelastic properties have been determined for poly(glycerol‐co‐glutaric acid) films synthesized from Lewis acid‐catalyzed polyesterifications. The polymers were prepared by synthesizing polymer gels that were subsequently cured at 125°C to form polymer films. The polymers were evaluated for the extent of reaction before and after curing by Fourier transform infrared spectroscopy. They were subsequently immersed in dimethylsulfoxide, tetrahydrofuran, water, methanol, and hexane for 24 h. The amounts of solvent absorbed were monitored and recorded. Dependent up the solvent used, the polymers were able to absorb 9.5–261% of its weight. The effects of the solvent absorption on the viscoelastic properties of the polyester films were evaluated by determining their elastic modulus (G′), viscous modulus (G″), tan δG″/G′, and complex viscosity (η*) by performing oscillatory frequency sweep experiments. The elastic modulus (G′) and viscous modulus (G″) were both higher for the dry polymers than the solvent‐absorbed polymers. However, the polymer films were all higher in elastic (G′) character than viscous (G″) character. Therefore, tan δG″/G′ < 1 before and after immersion in solvents. Values for η* decreased with angular frequency for all of the polyesters tested in this study. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012