Phase diagrams of thermoreversible gels

The molecular origin of at-PS cross-linking has been the subject of a number of works [14,16-19], but there still remains a divergence in opinions. One series of studies [16] postulate the existence of short crystallizable stereoregular segment sequences on polymer chains, even if they are atactic, that are responsible for the formation of microcrystalline junctions. 

Other studies [18,17] propose that cross-linking takes place by specific interaction, such as the formation of stoichiometric compounds involving solvent molecules. If such complex formations were the mechanism of cross-linking, the gelation temperature should show a maximum at the stoichiometric concentration [17]. Existence of specific interaction was later suggested by a light seattering study of at-PS dilute solution mixture of CS2 and toluene [20]. 

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