Cross-linking elasticity

What happens upon equilibration with liquid water instead of water vapor According to Equation (6.13), the capillary radius would go to infinity for PVP —> 1. Thus, in terms of external conditions, swelling would be thermodynamically unlimited, corresponding to the formation of an infinitely dilute aqueous solution of ionomer. However, the self-organized polymer is an effectively cross-linked elastic medium. Under liquid-equilibrated conditions, swelling is not controlled by external vapor... 

Natural rubber (Section 14.7) is the most common example tomer. Rubber has the long chains and occasional cross-links elasticity, but its irregular geometry prevents close packing of into crystallites. Gutta-percha, by contrast, is highly crystalline an elastomer (Figure 31.5). 

Figure 2.4. The lefthand side shows a representative sheet of y-irradiation cross-linked elastic-contractile model protein, designed for the conversion of an input energy into the output of pumping iron, per-...

Obviously, the effect of raising the temperature of a loaded, cross-linked elastic band composed of elastic protein-based polymers of the poly(GVGVP) family is to drive hydrophobic association with the consequence of lifting of the attached weight. How does this combine with the above understanding of elasticity to perform mechanical work ... 

Axiom 2 Heating to raise the temperature from below to above the temperature interval for hydrophobic association of cross-linked elastic model protein chains drives contraction with the performance of mechanical work. 

Acid-base Titration Curves for Cross-linked Elastic Matrices of poly[0.82(GVGIP),0.18(GEGIP)] at different extending forces... 

Figure 5.23. Mechano-chemical transduction exhibited by carboxyl-containing cross-linked elastic model protein (A) Stretch gives nonlinear increases in pKa values despite the linear stress-strain curve...

The same graphical insights utilized above can be used to obtain insight into relative efficiency. These can then be compared with the direct experimental determination of the efficiency of each polymeric system and of the relative efficiencies. The relative ApAn areas can be observed for the polymers as well as their Hill coefficients. Finally, the acid-base titration curves are given for the cross-linked elastic matrices held at fixed force and the change in length determined. 

Muscle and Cross-linked Elastic Protein-based Polymer, (GVGVP) , Contract on Raising the Temperature over the Same Temperature Range... 

Raising the temperature to drive contraction by hydrophobic association is the fundamental property of the consilient mechanism as demonstrated in Chapter 5 by means of designed elastic-contractile model proteins. Thermal activation of muscle contraction also correlates with contraction by hydrophobic association, but assisted in this case by the thermal instability of phosphoanhydride bonds associated with ATP, which on breakdown most dramatically drive hydrophobic association. In particular, both muscle and cross-linked elastic protein-based polymer, (GVGVP) contract on raising... 

Figure 9.46. y-Irradiation cross-linked elastic disks of X -(GVGIP)26o, equilibrated in dipropylene glycol/propylene glycol/H20 (2 1 1) and loaded with 0,0.1,1, and lOmg/cm dazmegrel, a thrombox-... 

Furthermore, yet to be computed by any program is the fundamental thermo-mechanical transduction wherein the cross-linked elastic-contractile model proteins contract and perform mechanical work on raising the temperature through their respective inverse temperature transitions. These results first appeared in the literature in 1986 and have repeatedly appeared since that time with different preparations, compositions, and experimental characterizations. Additionally, the set of energies converted by moving the temperature of the inverse temperature transition (as the result of input energies for which the elastic-contractile model protein has been designed to be responsive) have yet to be described by computations routinely used to explain protein structure and function. 

As seen in Figure 9B, at fixed extension of the y-irradiation-cross-linked elastic matrix comprised of poly[0.8(GVGVP), 0.2(GEGVP)], protonation of four carboxylates per 100 residues results in development of elastic force. A thermoelasticity characterization of this matrix at low pH gives the same result of dominantly entropic elasticity as found in curve b of Figure 6B for poly(GVGVP) in the absence of carboxyl moieties. 

Another alternative for decreasing rejection and infection rates is the creation of a biodegradable device. A biodegradable cross-linked, elastic salmon collagen scaffold with wall compliance similar to native artery has been used as a vascular graft. 

Wheat starch is composed of two components itself amylose, a linear, amorphous polymer and amylopectin, a branched, semicrystaUine polymer (10). The protein is known as gluten, also composed of two polymers, gliadin, a low-molecular-weight, soluble polymer and glutenin, a high-molecular-weight, cross-linked, elastic polymer primarily responsible for the viscoelastic properties of bread doughs. 

Elasticity is exhibited by materials of varying chemical composition. The primary condition for a material to be elastic is that it should predominantly consist of long linear molecules, i.e. it should have a large number of recurring units linked together by strong chemical bonds, and these should he cross-linked. Elasticity is apparently independent of whether these units are identical throughout the whole chain or whether other monomers are present. Properties other than elasticity, however, such heat and fluid resistance, will be markedly affected by the structure and type of flie chemical units involved in the chain. 

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