Thermoreversible gelation in solutions of syndiotactic poly-styrene (sPS) is investigated. Gelation in the solvents toluene, chlorobenzene, 1,2-dichlorobenzene, chloroform, 1,4-dioxane, tetrahydrofuran, o-xylene, cis- and trans-decalin is obtained by quenching the solutions in an ice bath.
Depending on the temperature and solvent-type, two gel types can be formed. Elastic, hazy gels (type I) can be obtained in all solvents by qnenching in an ice bath. Cooling of the solutions in cis- and trans-decalin to high temperatures, and heating of type I gels, leads to the formation of past-like, opaque gels (type II). This gel type melts at higher temperatures than gel type I.
The solvent-dependence of this behaviour is related to the stability domains in the temperature-concentration diagram of different crystalline modifications. In cis- and trans-decalin, a transformation from the helical phase (gel type II) to be zigzag phase (gel type II) can take place on heating.