Gels Swollen after Cross-Linking

Figure 3 Liquid crystalline (A) and gel-based alignment medium (B) at various stages (A) dry PBLG and the readily prepared lyotropic mesophase. (B) Cross-linked PS as an unswollen polymer stick in a standard NMR tube (left), polymer stick directly after polymerization, fully swollen polymer stick, polymer stick swollen in an NMR tube with an effective stretching along the tube axis (right). (Reproduced from refs. 17 and 53 with permission from Wiley-VCH Verlag GmbH Co. KGaA (Copyright).)...

The density of cross-links in the elastomer network was determined by the method of equilibrium swelling according to standard PN-74/C-04236. The samples of the composite material were subjected to equilibrium swelling in toluene for 48 h at room temperature. Then, the swollen samples were weighed on a torsion balance, next dried at a temperature of 60 to a constant weight and after 48 h they were reweighed. Based on the Flory-Rehner s equation [20] the crosslink density was determined, assuming the elastomer-solvent interactions parameter as x = 0.501 + 0.273 Vr, where Vr is the volume fraction of the elastomer in the swollen gel. 

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