Hydrogels crosslink density

M.J. Garland, T.R.R. Singh, A.D. Woolfson, and R.F Donnelly, Electrically enhanced solute permeation across poly(ethylene glycol)-crosslinked poly(methyl vinyl ether-co-maleic acid) hydrogels Effect of hydrogel crosslink density and ionic conductivity, Int. J. Pharm.,... 

Bian, L., Hou, C., Tons, E., Rai, R., Mauck, R.L., Burdick, J.A., 2013. The influence of hyaluronic acid hydrogel crosslinking density and macromolecular diffusivity on human MSC chondrogenesis and hypertrophy. Biomaterials 34,413 21. 

To determine the crosslinking density from the equilibrium elastic modulus, Eq. (3.5) or some of its modifications are used. For example, this analysis has been performed for the PA Am-based hydrogels, both neutral [18] and polyelectrolyte [19,22,42,120,121]. For gels obtained by free-radical copolymerization, the network densities determined experimentally have been correlated with values calculated from the initial concentration of crosslinker. Figure 1 shows that the experimental molecular weight between crosslinks considerably exceeds the expected value in a wide range of monomer and crosslinker concentrations. These results as well as other data [19, 22, 42] point to various imperfections of the PAAm network structure. 

Kofinas et al. (1996) have prepared PEO hydrogels by a similar technique. In this work, they studied the diffusional behavior of two macromolecules, cytochrome C and hemoglobin, in these gels. They noted an interesting, yet previously unreported dependence between the crosslink density and protein diffusion coefficient and the initial molecular weight of the linear PEGs. 

Hydrogel degradation time was controlled by the molecular weight obtained and the crosslink density of the material. 

In hydrogels can be measured and is a measure of polymer structure, crosslinking density, solvent content and polymer-solvent interactions, as can be seen from Table 8.6. 

Fig. 2 The modulus of elasticity Go, the effective crosslink density Vo (a) and the volume swelling ratio 2v of PAAc hydrogels in water (b) as function of the polymer network concentration ip2, 1.2 mol % MBAAm. The inset to Fig. 2a shows a double logarithmic Go vs. 9 plot. Reprinted from Yazici and Okay (2005) with kind permission from Elsevier...

Figure 10. Absorption of the VLPs VA387 by hydrogels of different crosslinker density A) controlled sample B) glycosylated hydrogel with 0.75% of crosslinker C) with 1.0% of crosslinker D) with 2.0% of crosslinker.

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