Gelation mechanism of syndiotactic polystyrene in bromoform

The gelation of sPS in bromoform was investigated with different techniques. Calorimetric results allowed to conclude that bromoform acts as a good solvent for sPS and that at low polymer concentration the formation of very strong, elastic gels is possible without interaction with the crystallization of the polymer. The conformational transition from coil into helix was followed by means of infrared measurements. The mobility change of the polymer chain during the transition was monitored by H-1 NMR. These results were compared with rheological measurements that detect the network formation. The results point to a two-step gelation mechanism where a single helix, formed in a first step, associates into multiple helices in a second step, thus forming the cross-links of the gel network.