Our gels are based on triblock copolymers with poly(methyl methacrylate) end blocks and a poly(n-butyl acrylate midblock). The structure of these materials has been studied by small angle x-ray scattering, and is reported in reference 44, along with a discussion of their application as adhesives. At temperatures above the gel point (about 60 °C), the materials are freely flowing polymer solutions. The following picture shows one of these solutions (including in this case a relatively high volume fraction of ceramic filler particles) being poured from a vial:

Below the gel point, which corresponds to the 'critical micelle temperature' (CMT) of the triblock copolymers, the PMMA end-blocks aggregate as illustrated in the picture below:

The relaxation time of the ordered gel is determined by the proximity to the glass transition temperature (Tg) of the PMMA domains. The overall transition from a low viscosity liquid to a high strength elastic solid is quite abrupt, and is due to the close proximity of CMT to Tg, as described in more detail in reference 60.

We have used these materials as model systems in our fundamental studies of the adhesion of soft elastic solids (reference 30, reference 31, reference 42). More recently, we have studied the large strain behavior of these elastic materials, and have shown that shape instabilities generally associated with the flow of a material are observed in purely elastic materials as well (reference 46). The elastic nature of these materials at room temperature is illustrated by the pictures below, which shows a gel being strained in tension to the point of fracture:

Gel strained in tension just prior to fracture

Fractured gel