Polystyrene-carbon disulfide gels

FRA Francois, J., Gan, J.Y.S., and Guenet, J.M., Sol-gel transition and phase diagram of the system atactic polystyrene-carbon disulfide, A/ocrowo/eew/es, 19,2755,1986. 

Figure 3(b) depicts the gel point of polystyrene-carbon disulfide systems and die plot at constant molecular weight shows good linearity. 

Irie M, Iga R. 1986. Photoresponsive polymers 9. Photostimulated reversible sol gel transition of polystyrene with pendant azobenzene groups in carbon disulfide. Macro molecules 19(10) 2480 2484. 

Ire and Iga demonstrated that photostimulated sol-gel transitions are possible with gels of a polystyrene copolymer in carbon disulfide solution that carry some azobenzene groups. The transitions are reversible and take place upon ultraviolet light irradiation. The polymer undergoes cis to trans isomerization of the pendant azobenzene groups with a 62% conversion for polymers containing as much as 10.5% of azo groups ... 

Figure 7.24 DSC curves for polystyrene (PS)-carbon disulfide (CSj) gels at various gelation times (25]. 1,10 min II, 20 III, 30...

A. Hiltner Yes. You just made an important point which is that this is a general phenomenon and should nc% be considered as typical of atactic polystyrene in carbon disulfide. Because the solvent obviously affects the thermodynamics, if one finds the proper solvent, any polymer should gel. Your other point which is that it could be intra- as well as intermolecular is absolutely correct, and we just see the manifestation as gelation when it s intermolecular and forms a netwtnk. That s why the overlap is necessary. 

R.F. Boyer Yes. If you plot the reversible gel temperature as a function of the solubility parameter, it goes through a pretty well-defined minimum, exactly at 9.1, which is the cohesive energy density of polystyrene. As for carbon disulfide seeming to be unique, the only unique thing about it is that it s way out on the high solubili parameter side relative to polystyrene (11 vs. 9.1). I think it fits in exactly as I understood die point you were trying to make. The reader is referred to a recent paper of ours for details [R.F. Boyer, E. Baer, and A. Hiltner, Macromolecules, 18, 427-434 (1985)]. 

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