Gels properties

R. S. Hadand, R. K. Pmd homme, Poly electrolyte Gels, Properties and Applications, American Chemical Society, Washiagton, D.C., 1992. 

The theories of Miller and Macosko are used to derive expressions for pre-gel and post-gel properties of a crosslinking mixture when two crosslinking reactions occur. The mixture consists of a polymer and a crosslinker, each with reactive functional groups. Both the polymer and crosslinker can be either collections of oligomeric species or random copolymers with arbitrary ratios of M /Mj. The two independent crosslinking reactions are the condensation of a functional group on the polymer with one on the crosslinker, and the self-condensation of functional groups on the crosslinker. 

In this paper a simple BASIC program for calculating pre-gel and post-gel properties of thermoset coatings has been presented. The program is based on the work of Miller and Macosko and has been extended to incorporate two independent crosslinking reactions. In... 

As might be expected, these differences in the pre-gel properties are also reflected in the post-gel regime. The sol fraction varies more smoothly with conversion for the branched prepolymer compositions, cf. Figures 3 and 6. But because the gel point is at (so... 

Small variations in the conversion of A in the first stage (but a complete conversion of h in stage 2) have a very significant impact on the characteristics of P2 and on the pre- and post-gel properties in stage 3. This is exemplified in Figures 12-14. 

Michov, BM, Radically Simplifying the Henry Eunction, Electrophoresis 9, 199, 1988. Miller, DR Macosko, CW, A New Derivation of Post Gel Properties of Network Polymers, Macromolecules 9, 206, 1976. 

Serwer, P, Agarose Gels Properties and Use for Electrophoresis, Electrophoresis 4,375,1983. 

Tanaka, T, Phase Transitions of Gels. In Polyelectrolyte Gels, Properties, Preparation, and Applications, ACS Symposium Series Harland, RS Prud homme, RK, eds. American Chemical Society Washington, DC, 1992 Vol. 480, p 1. 

Tietz, D, Evaluation of Mobihty Data Obtained from Gel Electrophoresis Shategies in the Computation of Particle and Gel Properties on the Basis of the Extended Ogston Model, Advances in Electrophoresis 2, 109, 1988. 

The gel properties will also be influenced by many other parameters including the nature of the cross-links, synthesis conditions, type and concentration of initiator used, phase separation, and the presence of noncovalent interactions such as hydrogen bonding and hydrophobic interactions. Nonetheless, the gel properties depend primarily upon the monomers used. 

DR Miller, CW Macosko. A new derivation of post gel properties of network polymers. Macromolecules 9 206-211, 1976. 

Time-resolved measurements on the changing sample have the advantages that the critical gel properties can be obtained from a single experiment and that a value for the rate of evolution of properties comes with the data. 

From a practical point of view, it is advantageous that critical gel properties depend on molecular parameters. It allows us to prepare materials near the gel point with a wide range of properties for applications such as adhesives, absorbents, vibration dampers, sealants, membranes, and others. By proper molecular design, it will be possible to tailor network structures, relaxation character, and the stiffness of gels to one s requirements. 

Oppermann, W., Swelling Behavior and Elastic Properties of Ionic Hydrogels, in Polyelectrolyte Gels Properties, Preparation, and Applications (R. S. Harland and R. K. Prud homme Eds.), pp. 159-170. American Chemical Society, Washington (1992). 

The gel properties as well as the gelling conditions are radically different for the two types of pectin. High methoxyl pectins produce a gel that does not remelt, while some low methoxyl pectin gels are thermoreversible. 

The determination of the kinetic regularities for different systems is important in the first turn for understandina of the process of the networks formation and for the study of sol and gel properties. On the other hand, the solution of the kinetic problem is of the great importance from the viewpoint of the further development of the general theory of macromole-cular reactions. 

Mixing different cross-linkers (19b and 19c) yielded systems with a strong gel-weak gel transition, rather than a distinct sol-gel shift. When the concentration of each of the cross-linkers was above the critical percolation threshold, the kinetically slower cross-linker (19c) dictated the gel properties. Upon addition of enough of a competitive binding additive, such as DMAP, to drop the concentration of the active cross-linking units below their individual percolation thresholds but still allowing the total amount of both active cross-linkers (19b and 19c) to be above the percolation threshold results in a gel whose properties are now controlled by the kinetically faster cross-linker (19c). 

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