I am looking for some literature on critical gels. I did get my hands on the detailed work by Winter and Chambon. They stop polymerization to produce a critical gel state. However I have not come across much work on physical gels that are in a critical state. Is it possible to prepare and retain a physical gel system that is at the critical stage? Are there reports of systems that provide imaging/ visualization insights into the sol/gel transitions?
Apparently you have in view of obtaining a sol of the polymer from its solution (gel) under spinodal decomposition. The separation in the polymer / solvent system occurs on the spinodal. The critical state of the system is reached on the spinodal. It is better to get acquainted with this voice with a lecture
http://www.eng.utah.edu/~lzang/images/lecture-22.pdf
In my opinion, you cannot keep a physical gel in the critical state. I'm thinking of systems like gelatin or carrageenan. Since such systems age, they cannot be held in any particular state. They are continuously evolving.
I don't know of any visualization studies - it's difficult - maybe using electron microscopy after ultra-rapid cooling, using slushy propane or whatever. In any case, I don't think that visualization is very helpful. The subtle changes in connectivity close to the sol/gel transition are not obvious to the eye.
The critical gel in physical system can be observed using rheological experiment. I have worked on one of such system which show physical gelation. We used Winter-Chambon criteria to observe the critical gel state. However keeping a physical gel at the critical gel state is not possible, as it will keep on evolving to gain it's strength. We have also shown a evolved gel network state using cryo-TEM. It is difficult to do imaging of critical gel because it is most fragile state of a gel.
Look at literature on thermoreversible sol-gel transition in physical gels. In such case, you can retain the critical state if you maintain the constant temperature.
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