Critical gelation concentration

Pronounced self-assembly of 281 and 282 in nonpolar solvents (e.g., aliphatic and aromatic hydrocarbons) takes place as a result of hydrogen bonding between amide groups to result in the formation of gels above a critical gelation concentration. 

GAG) for the associative thickener. Although it is tempting to call this the critical gelation concentration, this name would be misleading as systems a little above this concentration were observed to phase-separate into a lower gel phase and an upper lower viscosity phase if left to stand for a time in excess of 2 weeks. The increased slope of the T red vs. c plot for c > 0.075 g dL" is a clear indication of very extensive aggregation. 

In the presence of a selective solvent, ordered block copolymers form micelles that, at sufficiently high copolymer concentrations, serve to stabilize a diree-dimensional network and promote physical gelation. This study examines the steady and dynamic rheological properties of micellar solutions composed of AB diblock, ABA triblock and bidisperse mfactures of AB and ABA copolymer molecules. Of particular interest is the unexpected improvement in network development upon addition of an AB copolymer to an ABA copolymer at constant solution composition. This behavior is observed for ABA/solvent systems above and below the critical gelation concentration, and is interpreted in terms of the volume exclusion that occurs in bidisperse mixture of grafted chains. 

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