Polyhedral Oligomeric Silsesquioxanes Surfactants
Abstract
There has been recent interest in using polyhedral oligomeric silsesquioxanes (POSS) as the smallest particles of silica for reinforcement of polymers. These materials are monodisperse, have tailored functionality (including a hydrophobic coating) and should thus act as model nanoparticulate filler. Feher et al have shown that sol-gel condensation into cage compounds can yield two thermodynamically stable main isolates: a fully condensed R8T8 cube and an incompletely condensed R7T4D3(OH)3 trisilanol. (T refers to a SiO3/2 and D is a SiO2/2 moiety in a silicate framework) There are large differences in the solubility of POSS in common organic solvents based on the substitution of the cages. For example, a fully condensed iBu8T8 cube is more soluble than a similar cyclohexyl Cy8T8 cube which in turn is more soluble than a cyclopentyl Cp8T8 substituted cube. Furthermore the breaking of symmetry in the incompletely condensed cubes could also be expected to enhance solubility/compatibility. The dispersion of POSS will likely determine how well the material can act as a "nanofiller." Farmer et. al. have recently performed molecular dynamics simulations which suggest that POSS molecules have no tendency for aggregation in a polymeric matrix if they are originally well dispersed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2001
- Accession Number
- ADA410399
Entities
People
- Alan Esker
- Brent D. Viers
- Katie Farmer