The Critical Gel

Nature allows polymers to pass through the gel point with striking simplicity and elegance. However, what are the rheological properties at the gel point? Is the polymer at the gel point, the ‘critical gel’, at a distinct material state that has its own properties? It seems that these questions, until recently, have not been pursued. The questions might have been avoided since it was well known that the established rheological concepts fail altogether at the gel point: the concept of a viscosity is inapplicable since the viscosity diverges to infinity and the concept of an equilibrium modulus is useless since the modulus is still zero at the gel point. The gel point itself had remained mysterious.