Temperature hydrogels

Figure 2. Swelling ratio of poly(DMAEMA) hydrogels in deionized water as a function of temperature. Hydrogels were prepared by bulk polymerization with 1.0wt% EGDMA as a crosslinker.

Hydrogels. Controlled swelling of hydrophilic polymers, derived from the glossy/mbbery properties of polymers, is used to control the rate of dmg release from matrices. In the mbbery state, accompHshed by lowering the polymer s glass-transition temperature to an appropriate level, the dispersed dmg diffuses as the polymer swells in the presence of water. 

Chatterjee S., Bohidar H.B. 2005. Effect of cationic size on gelation temperature and properties of gelatin hydrogels. International Journal of Biological Macromolecules 35, 81-88. 

Spherical microparticles are more difficult to manufacture and can be prepared by several methods. One method prepares silica hydrogel beads by emulsification of a silica sol in an immiscible organic liquid [20,21,24,25]. To promote gelling a silica hydrosol, prepared as before, is dispersed into small droplets in a iater immiscible liquid and the temperature, pH, and/or electrolyte concentration adjusted to promote solidification. Over time the liquid droplets become increasingly viscous and solidify as a coherent assembly of particles in bead form. The hydrogel beads are then dehydrated to porous, spherical, silica beads. An alternative approach is based on the agglutination of a silica sol by coacervation [25-27], Urea and formaldehyde are polymerized at low pH in the presence of colloidal silica. Coacervatec liquid... 

DC Harsh, SH Gehrke. Controlling the swelling characteristics of temperature-sensitive cellulose ether hydrogels. J Controlled Release 17 175-186, 1991. 

X Huang, H Unno, T Akehata, O Hirasa. Analysis of kinetic behavior of temperature-sensitive water-absorbing hydrogel. J Chem Eng Jpn 20 123-128, 1987. 

A Afrassiabi, AS Hoffman, LA Cadwell. Effect of temperature on the release rate of biomolecules from thermally reversible hydrogels. J Membrane Sci 33 191-200,... 

Even though, structure and dynamics are most important to characterize hydrogels, protein fibrils, and membrane proteins, they cannot be simultaneously determined. We emphasize here the importance of the dynamic aspect mainly available from NMR measurements at ambient temperature, even though structural data can be obtained more easily at lower temperatures under suppressed dynamics. 

---