Triple-network gels

Fig. 22 Phase-contrast micrographs of BFAECs cultured on double network (DN) and triple network (TN) gels PNaAMPS/PDMAAm DN gel (a), PNaAMPS/PDMAAm/poly(NaAMPS-co-DMAAni I TN gels (b-d). In the third network. NaAMPS molar fraction was F = 0.5. The cross-linker concentration of the third network was 0 (a), 2 (b), and 4 mol% (c). Scale bar. lOOpm. (Reproduced, with permission, from [98])...

At low temperatures the nematic gel coexists with excess solvent, i.e., the i-N biphasic coexistence. Above the triple point TJ, excess solvent coexists with an isotropic gel, i.e., the i-I coexistence. Also, above this temperature, the isotropic and the nematic phases of a gel can coexist, i.e., I-N phases. Beyond the phase gap, a single nematic phase exists. The I-N region terminates at the = 1 axis. This is at T the N-I transition temperature of the undiluted network which, in turn, is close to Tni, the transition temperature of the uncrosslinked polymer melt from which the network derives. The nematic order is not expected for any 4> for T above. This is the limit of stability for even the undiluted case. 

---