APPLICATIONS: Detection of nerve agents and explosives, surface acoustic wave sensor coatings, fuel cell membranes

IN A NUTSHELL: Polyhedral oligosilsesquioxanes (POSS) are stoichiometrically well-defined cage compounds prepared by the hydrolysis and condensation of trifunctional silanes of the form RSiX3, and are often described as a nanoscale form of silica. The condensation reactions can generate products ranging from small molecules, oligomers, and clusters to resins of highly complex structure, and the products obtained are highly dependent upon silane and water concentration, pH, temperature, solubility and catalyst.

Correct control of these variables results in the most common T8 form of POSS (Figure).  R8Si8O12 is a fully condensed compound with a distance of 1.5 nm between R groups on adjacent corners of the POSS cage.  POSS compounds carrying a variety of simple functional groups are commercially available from suppliers such as Hybrid Plastics, and Oxazogen has expertise in using these basic building blocks to create POSS compounds carrying smart groups that can be deployed in other materials systems and that can enhance their performance.

POSS functionalized with hydrogen-bond acidic resonant sensor groups (BSP3 POSS, FPOL POSS, SXFA POSS, Phenol POSS)

In order for array-based resonant chemical vapor sensors such as SAW sensors to collect the most chemical information, each element in the array must be coated with a different material. The collection of coatings must cover the full range of solubility interactions (dispersion, dipole-dipole and hydrogen-bonding), and needs to include non-polar, polarizable, dipolar, hydrogen-bond basic and hydrogen-bond acidic coatings.

Most materials exhibiting these types of interactions are commercially available, except for hydrogen-bond acidic materials which are essential for the detection of hydrogen-bond basic entities such as nerve agents and explosives. Normally, linear polymers carrying phenol or fluorinated aliphatic alcohol groups are used in hydrogen-bond acidic SAW coatings, but good sensor polymers do not necessarily make robust coatings.
In this line of products, hydrogen-bond acidic sensor groups have been placed on polyhedral oligosilsesquioxane nanofillers which can be formulated into a carrier polymer to give a reinforced SAW sensor coating. It has been shown that SAW sensors coated with sensor nanofiller formulations maintain better performance over time than SAW sensors coated with conventional linear polymers.

POSS functionalized with proton-conducting sulfonic acid groups for fuel cell membranes (S-POSS)
In this product, proton-conducting groups have been placed on a polyhedral oligosilsesquioxane (POSS) nanofiller which can be formulated into existing fuel cell proton exchange membranes, resulting in improved conductivity at low humidity and more robust physical properties.