Mechanistic aspects of the thermoreversible gelation of syndiotactic poly(methyl methacrylate) in toluene

The thermoreversible gelation of syndiotactic poly(methyl methacrylate) in toluene has been investigated in detail. The two-step mechanism, proposed i n an earlier publication, has been confirmed and illustrated in detail thro ugh the combination of FTIR investigations and rheological and NMR observat ions. The basic steps of this gelation mechanism are the equilibrium coil-t o-single helix transition (first step) and the helix association into dimer s (second steps) and larger multichain association units. The coil-to-helix transition is a true equilibrium process that can be detected separately t hrough kinetic trapping. The comparative analysis of the infrared and rheol ogical data and the temperature dependence of the line widths of the H-1 si gnals support the validity of this proposition.