Critical Concentration for Gelation

An interesting dependence of CS on the molecular weight of precursor FPs was found in the case of rigid aromatic polyamides. A series of FPs was 

It is interesting to note that, although we could not prepare networks from FPs at Co eg, networks prepared at Cq Cg could be swollen in a good solvent 

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A limited biopolymer incompatibility under the conditions of pH (7) and low biopolymers concentration may contribute to increased hardness and thermal properties of gels. Excluded volume effects favour gelation of hydrocolloids. For incompatible biopolymers in mixed solutions, the rate of gelation is higher and the critical concentration for gelation is lower than for each of them individually.18,19... 

Acetate Branches Butyl Branches Appearance Critical concentration for gelation ... 

When the molecular weight distribution of the original carboxy telechelic polymer is very narrow, the increase of the solution viscosity is very sharp and the critical concentration for gelation (Cgel) is accurately determined by the vertical asymptote of the log n rel vs. concentration curve. 

Van der Linden and Sagis (2001) have suggested that, once a critical concentration for gel formation is known, one can predict, for example, the dependence of the gel elasticity on the concentration of protein. The minimum gelation concentration may be expressed in terms of the basic fibre characteristics like the stiffness and also as a function of salt concentration (Veerman, 2004 Sagis et al., 2004). It is pointed out by van der Linden (2006) that there are two important factors which allow the manipulation of this minimum gelation concentration to an extremely low value. The first factor is that the nano-fibre should be robust against dilution. And the second is that the fibre should robust also with respect to other treatments, especially the adjustment of the pH. It would appear that each of these conditions is satisfied. 

Finding the critical concentration of gelation for the PVA cryogels case... 

Observations from this viscosity study and previous studies with other gel systems suggest that there is a minimum polymer concentration for gelation for a particular polymer. Below this concentration, IMC may be overwhelming. For the Aldrich polyacrylamide, this minimum concentration appears to fall somewhere between 2000 and 4000 ppm. The minimum concentration is suspected to be related to the critical overlap concentration commonly used to describe the transition between a dilute solution and a semi-dilute solution. The critical overlap concentration for the Aldrich PAAM was estimated from its intrinsic viscosity (5.0 g/dl)... 

Protein Concentration. For a given type of protein, a critical concentration Is required for the formation of a gel and the type of gel varies with the protein concentration. For example, gelatin and polysaccharide solutions will form gels at relatively low concentrations of the gelling material. Considerably higher protein concentration Is usually required for the gelation of globular proteins. 

Percolation describes the geometrical transition between disconnected and connected phases as the concentration of bonds in a lattice increases. It is the foundation for the physical properties of many disordered systems and has been applied to gelation phenomena (de Gennes, 1979 Stauffer et al., 1982). At just above gelation threshold, denoting the fraction of reacted bonds as p and p=Pc + A/ , pc the critical concentration (infinite cluster), the scaling laws (critical exponents) for gel fraction (5oo) and modulus E) are ... 

By decreasing monomer and initiator concentration it is possible to eliminate gelation because polymers which form gels by crystallization from solution do so at a critical concentration and molecular weight ] ). The effect of monomer and initiator concentration for the polymerization reaction at 34°C is also shown by the data in Table V. 

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