Thermoreversible gelation of polyethylene/decalin mixtures by self-nucleated crystallization

Abstract

The critical gelation concentration of polyethylene gels formed in decalin by self-nucleation was studied as a function of the gelation temperature, the polymer dissolution temperature, and the time at the dissolution temperature. A comparison was also made with gels formed after cooling from a high temperature. The morphology of the various gels was examined to elucidate the gelation behavior. Self-nucleation of crystalline polymers in solution produces efficient gels that have a low critical gelation concentration and are relatively stronger at higher polymer concentrations than gels produced otherwise. The efficiency arises from the structural unit being a single lamella (but not necessarily a single polymer crystal) and by neighboring lamellae tending to rotate in solution to approach coplanarity, which allows an extensive attachment area between the lamellae. In addition, the lamellae in the gels appeared to all have the same size, and the critical gelation concentration was found to be relatively independent of the lamellar size.