  When two bubbles submerged in a liquid are brought closely together, the
intermediate liquid film separating the bubbles begins to drain. Once the film
ruptures, the bubbles coalesce and form a neck that expands with time. The
dynamics of the neck growth are well understood in the context of pure,
Newtonian liquids. Yet, much less is known about the dynamics of this
singularity when the surrounding liquid contains long flexible polymers, which
provide viscoelastic characteristics to the liquid's properties. Here, we
experimentally study the coalescence of bubbles surrounded by polymer
solutions. In contrast to drop coalescence, and in spite of the singular
stretching of polymers, we find that the presence of the dissolved polymers
does not at all affect the coalescence dynamics at early times. The polymer
elasticity is found to slow down the flow only during the later stages of
coalescence. These observations are interpreted using an asymptotic solution of
the Oldroyd-B model, which predicts a strong stress singularity near the
extremity of the neck. However, the polymer stress turns out to diverge only in
the azimuthal direction, which can explain why elastic effects remain
subdominant during the initial stages of coalescence.
