Secondary minimum state colloids

A definite prediction of DLVO theory is that charge-stabilized colloids can only be kinetically, as opposed to thermodynamically, stable. The theory does not mean anything at all if we cannot identify the crystalline clay state (d 20 A) with the primary minimum and the clay gel state (d 100 to 1000 A) with the secondary minimum in a well-defined model experimental system. We were therefore amazed to discover a reversible phase transition of clear thermodynamic character in the n-butylammonium vermiculite system, both with respect to temperature T and pressure P. These results rock the foundations of colloid science to their roots and... 

While it has been stated that there are inherent limitations in the DLVO theory, it does appear to be useful in explaining adhesion and contact in some biological cell systems. An early paper by Van den Tempel in 1958 showed that the theory could be used to analyze systems that were similar to colloidal ones. His work on emulsified oil globules, in relation to contact phenomena, enabled him to set up equations of repulsion and attraction resulting from the double layer. These equations, which are a direct result of the DLVO theory, have been applied with great success to biological systems. Van den Tempel was able to measure the thickness of the double layer and he confirmed that the secondary minimum predicted in the DLVO theory does exist. 

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