Overshooting Effect of Poly(Dimethylaminoethyl Methacrylate) Hydrogels

An overshooting effect was observed during the swelling procedure of poly(dimethylaminoethyl methacrylate) (PDMAEMA) gel for the first time. The effects of the temperature, ionic strength, and pH on the overshooting effect of the PDMAEMA gel were investigated. We found that the overshooting effect of the gel could not be eliminated by changing the temperature; however, the overshooting effect was indiscernible in high-concentration NaCl solutions (> 0.2 mol/L) and basic (pH 11.9) and acidic solutions (pH = 2.1). The overshooting effect of the PDMAEMA gel was attributed to the dynamic conformational changes of the side chains of dimethylaminoethyl methacrylate (DMAEMA) units during the swelling of the gels. In the presence of NaCl or NaOH, the stretching of the macromolecular chains of the gels was disrupted. While in acidic solution, the protonation of tertiary amino groups in the DMAEMA units made the side chains of the DMAEMA units change from the cyclic conformation to the stretched one; this was analyzed with the aid of Fourier transform infrared spectroscopy. (c) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2027-2033, 2011