Sponge-like gel

Breulmann, M., Colfen, H., Flentze, FI.-P Antonietti, M., Walsh, D. and Mann, S. (1998) Elastic Magnets Template controlled mineralization of iron oxide colloids in a sponge-like gel matrix. Advanced Materials 10 237-241. 

On the other hand, according to the results obtained by energy dispersive X-ray analysis (EDAX), a uniform distribution of TPA along bead radius was obtained. The secondary electron micrographs of the bead inner shows an sponge-like gel structure. 

In case of a porous gel, the collapsed network chains form a thicker layer. It acts as a barrier and prevents shrinking processes. The shrinkage barrier separates the inner swollen part of the gel from the outer part. The shown distribution of solvent inside the sponge-like gel was measured three days after immersion it into water/methanol. 

Fig. 29 Distribution of water inside a collapsed PNIPAAm gel. The volume phase transition was induced by per-deuterated methanol. The figures show Fourier images (slice selection, T2-weight-ed) of a vertical plane of PNIPAAm swollen in D2O. Distribution of water inside (a) a homogeneous gel and (b) a sponge-like gel. (c) Structure of the sponge-like gel (FESEM micrograph), scale bar 250 nm. 1 D2O/CH3OD environment 2 collapsed skin 3 shrunken gel (shrinkage barrier) 4 swollen gel. Reproduced from (Arndt et al. 2006), Fig. 7, p.l88, with kind permission of Springer Science and Business Media...

The final products of such cryostructuring are macroporous, sometimes wide-pore sponge-like, gel matrices, i.e., cryogels. 

Figure 29 Distribution of water in collapsed PNlPAAm gel, deswelling induced by methanol. Fourier images (slice selection, T2 weighted) of a vertical plane of PNlPAAm gels, (a) Homogeneous gel and (b) sponge-like gel after 3 days in D2O/CH3OD. Reproduced from Arndt, K.-F. ...

Gels of low concentration (0.1 -1.0%) give separated droplets and myelin. At concentrations above 4.5% the gels turn into a sponge-like continuous network of sheets and stands with small amounts of droplets and myelin. Amylose and amylo-pectin also undergo coacervation.277... 

Transparent anatase Ti02-based multilayered photocatalytic films synthesized via a sol-gel process on porous alumina and glass substrates showed a sponge-like microstructure and a mean crystallite dimension of ca. 8 nm [152]. Doping such films with iron(III) impeded the photocatalytic activity. 

The sponge-like structure of CPG probably also explains why its resistance to pH is a little higher than that of silica gel. The solublity of SiOj increases with pH, but in the case of CPG this process rarely interferes with normal laboratory operation unless pH exceeds 9.0 or even 9.5. For silica gel pH above 8.0 is significant - see Fig. 4. 

Irradiation of a high concentrated solution (again above overlap concentration) yields to a porous sponge-like macroscopic gel. Gels with high porosity show a fast swell kinetic (Arndt et al. 2001b). 

Fig. 12 shows micro-gel particles cross-linked by irradiation of a phase- separated solution in the two differently swollen states, at 25°C in a highly-swollen state and at 40°C at low degree of swelling. For details see (Amdt et al. 2001a). Irradiation of a high concentrated solution results in a bulky hydrogel with typical dimension in the cm-range. The sponge-like stmcture of the formed PVME hydrogel (irradiation of a PVME-solution in the phase-separated state) at different temperatures (swollen above and below the volume phase transition temperature) is shown in Fig. 13. The irradiation dose was 50 kGy.

Suspension polymerization, in which a mixture of monomers and crosslinking reagents is polymerized in the presence of an inert solvent, is used to prepare porous polymer beads [148]. The microstructure of the gel, formed within the droplet in the early stages, gradually grows into a sponge-like structure, with inert solvent filling the space between the microstructures. After solvent removal, the porous structure remains, pro-... 

It may be conceivable that the structure formation of barnacle adhesive is determined by critical self-assembly concentrations of the adhesive proteins within an interfacial gap between a barnacle base and a substrate. It can further be suggested that the biopolymers form coherent gel structures, in which two transitions of critical protein concentrations determine the arrangement of adhesive globules from a dense sheet-like formation to a slightly loose sponge-like formation to a very loose branched or web-like structure. 

Ti-TUD-1 Sponge-like pore structure TBOT TEOS TEA TEA, Ti fi-butoxide, TEAOH and aging and heating dry gel in autoclave Room temperature, 1—4 days Shan, 2001 (47)... 

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