Dear Mahesh,

In my understanding, a polymer gel is a three-dimensionally crosslinked polymer network swollen by a solvent, most typically water (then it is named "hydrogel").  By contrast, a particulate gel, which I better know under the name "colloidal gel", is a suspension of colloidal particles at volume fractions where particle movement is largely restricted, thereby leading to a solidlike system.  In this latter case, the gel state is pretty similar to the glass state, and it depends on the particle volume fraction which one is present.

According to this definition, I would assume(!) the metal alkoxides that you refer to to be a particulate gel.

Here's two review papers on both these different classes of gels:

Ann. Rev. Cond. Mat. Phys. 2013, 4, 217.

Adv. Polym. Sci. 1997, 130, 1.

Greetings,

Sebastian Seiffert

Dear Maresh.

This was well-explained by Brinker & Scherer see: http://depts.washington.edu/solgel/documents/class_docs/MSE502/Sol-Gel_Science_The_physics_and_chemistry_of_sol-gel_processing_-_Brinker_1990.pdf           (roughly at page 102and further)

A polymeric netwok consist of weakly branched chains that have a low fractal dimension as it is the case for acid catalyzed silicon alkoxides. This wire-like structure that contains micropores typically smaller than 3 nm.

An particulate gel is an assembly of dense spherical particles as it is the case for base catalyzed silica. These materials exhibit lager pores >3nm and are meso or macroporous.

Metal alkoxides or other metal oxide precursors typically form particulate gels. This due to the tendency of metals to favor high coordination numbers and therefore form dense spherical primairy particles. It is a general belief that coordination number can be surpressed by chelating agents and affect the type of gel being formed. Nevertheless, these statements have been questioned by a critical review of Vadim Kessler et al. see: Kessler, V. G.; Spijksma, G. I.; Seisenbaeva, G. A.; Håkansson, S.; Blank, D. H. A.; Bouwmeester, H. J. M., New insight in the role of modifying ligands in the sol-gel processing of metal alkoxide precursors: A possibility to approach new classes of materials. J. Sol-Gel Sci. Technol. 2006, 40 (2-3), 163-179.

greetings, rogier

thank you sir for your valuable time and answers

Here is an excellent reference which defines all there terms [Pure Appl. Chem., Vol. 79, No. 10, pp. 1801–1829, 2007.

doi:10.1351/pac200779101801]. What I don't know is what the difference between a gel and an elastomer is. A gel is often defined as a viscoelastic fluid where the storage modulus is greater than the loss modulus. An elastomer is viscoelastic/viscoplastic but is not necessarily a fluid. Can anyone shed more light on this?