Gelation polymer gels

Ross-Murphy, SB, Physical Gelation of Synthetic and Biological Macromolecules. In Polymer Gels, Fundamentals and Biomedical Applications DeRossi, D Kajiwara, K Osada, Y Yamauchi, A, eds. Plenum Press New York, 1991 21. 

Menjivar, J.A. "On the Use of Gelation Theory to Characterize Metal Crosslinked Polymer Gels," Chapter 13, Advances in Chemistry Series 213, American Chemical Society, Washington, DC 1986. 

Horton, J. C., and Donald, A. M. (1991). Gelation in a synthetic polypeptide system. In Food Polymers, Gels and Colloids, Dickinson, E. (Ed.), pp. 508-512. Royal Chem. Soc., London. 

According to the Flory-Stockmayer (29a) theory of gelation, the gel point, corresponding to the formation of an infinite network, is reached when one cross-link per initial polymer molecule present has formed. 

Ozaki K, Sugino H, Shlrasakl Y, Aokl T, Arakawa T, Funatsu T, Shoji S (2010) Microfluidic cell sorter with flow switching triggered by a sol-gel Transition of a therm-resersible gelation polymer. Sens Actuators B 150 449 55... 

Gelation rate, gel strength, and long term gel stability are the gel properties that describe gelation. As mentioned previously, there are many system variables that can affect gelation. Temperature, crosslinker properties, polymer properties, water properties, and shear all have major effects on gelation. Z.11.14.1 -19.21-, ... 

J. A. Menjivar, On the Use of Gelation Theory to Characterize Metal Crossllnked Polymer Gels, Polym. Mater. Sci. Eng., 51 88 (1984). 

The sequence in the treatment of a core with a polymer gel system is similar to that just described and typically involves three steps. First, the initial permeability of the core sample is measured with brine. Then the core is treated with a polymer/crosslinker solution at a constant rate using a dual piston HPLC pump and a transfer cell (see Figure 5) while monitoring pressure with a differential pressure transducer. The core effluent is fractionated for analysis. This includes the determination of polymer and crosslinker concentration, the measurement of sample gelation tendencies, and the investigation of rock/polymer interactions. Finally, after a waiting period to allow gelation, the final permeability of the core is measured with brine to evaluate the effectiveness of the treatment. 

Polymer gels can be formed by physical connections or by chemical crosslinks. A physical polymer gel may be formed when solvent is added to a lyophilic polymer but in insufficient amount to completely dissolve the individual polymer molecules. Then, crystalline domains still remain and connect the flexible chains. Also, changing environmental conditions such as pH, ionic strength, solvent polarity, and the like may trigger the transition from a molecular solution into a gel, or vice versa. In those cases, the gelation process is often caused by a coil-to-helix transition in some parts of the polymer molecules. The helical parts tend to associate because they have a low solubility due to their relatively low conformational entropy in solution. Some proteins may form physical gels. The most well-known example is gelatin. 

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