Effects of temperature and molecular weight on the porous structure formation of polymer chemical gels

The effects of temperature and molecular weight on the formation of inhomog eneous polymer gels, in which chemical gelation and phase separation take p lace simultaneously, were investigated. Slow chemical gelation by gamma ray irradiation was suitable for systematic analysis. In starting from ordinar y polymer solutions, the characteristic wavenumber of the porous structure decreases very sharply with depth of temperature jump. However, with approp riate amount of pre-dose, the effects of temperature are almost taken over by those of the pre-dose. The shape of the phase boundary also contributes to this temperature insensitive region. Hence, pre-dose of polymer solution s, which induces the molecular weight build up, is an important factor that facilitates controlled preparations of inhomogeneous porous structures of chemical gel networks.