Bursting Dynamics of Thin Free Liquid Films from Newtonian and Viscoelastic Solutions

During the last decade, attention to confined liquid layers increased rapidly. This is explained by very different properties of these systems compared to their bulk analogies—thin and ultrathin films demonstrate an enhanced viscoelastic behavior (see, for example, [1‐ 6]). In the present Letter, we investigate the bursting behavior of very thin films from Newtonian and viscoelastic solutions, which cannot be explained within the frame of existing theories. In [4], we have improved the experimental setup of McEntee and Mysels [7], and reported a few new features of the rupture dynamics of very thin films from Newtonian and viscoelastic solutions. In those experiments, rupture was initiated by an electric spark, which triggered simultaneously a high-speed cine-photoflash. In the latter, a nanosecond pulse generator activates periodically a light flash with repeating capability of about 10 4 s 21 with an accuracy within 2%. With our setup, one can follow the evolution of a hole in a liquid film on one single photo. This allows observing additional fine details of the dynamic rupture process, which were not reported before. We have carried out experiments with free liquid films drawn from Newtonian, sodium dodecylsulfate (SDS) solutions and from viscoelastic cetyl-trimethyl ammonium bromide (CTAB-gel) solutions as well. Films from CTAB-gel up to ,1 mm thickness burst with a significantly lower velocity than that predicted by Culick [8], but for thicker films a transition to a Culick-like behavior occurs. The main new feature, that all CTAB-gel films demonstrate, is a deceleration of the rupture process. This deceleration becomes more pronounced as the film thickness decreases. Also, films of the “equilibrium” thicknesses have a scalloped appearance of the rim, which was discussed in more detail in [4,5]. In Fig. 1, a typical result of experiments with the Newton-black film of a Newtonian solution (a) and of a CTAB-gel solution (b) as well, is presented. The pictures closely resemble each other, suggesting that both systems on this length scale have many common features, which determine the overall macroscopic behavior of these very