Polyhedral oligomeric silsesquioxanes (POSS), a class of nanomaterials, are inorganic, highly crystalline, three-dimensional building blocks based on a silicon cubic cage nanostructure. POSS nanoparticles have been used as fillers in composite materials for a wide range of applications for optical and electrical devices, aerospace, biomaterials, and nanocomposites due to their nanoscale size, flexible functionality and biocompatibility.
The control of the interactions between nanomaterials and matrixes toward advanced nanocomposite materials must be achieved through specific modifications of the surface of nanomaterials. Such control may allow for improved dispersion or loading of nanomaterials within the main matrix and good adhesion between nanomaterials and the matrix, providing invaluable opportunities towards the design of materials with custom-designed thermo–electrical, mechanical, or catalytic properties. Current production methods to functionalize POSS, include hydrolysis and condensation from silica derivatives and functionalization from pre-formed POSS cages by chemical reactions. These methods are generally lengthy, require costly chemicals, lead to a range of sub-products, and produce environmentally unfriendly waste effluents.
Chemical structure of octa-methyl POSS and theoretical schematic plasma process for amine functionalization. The arrow with the indication CW + P Plasma denotes three steps of the process: step 1) continuous wave Ar plasma, step 2) N2/H2(15%) continuous wave plasma, and step 3) pulsed plasma with the same feed composition.
In a new study, an innovative and cost-effective alternative technique for the plasma functionalization of POSS micro-powders without damaging the cage structure is proposed for the first time.
Australian and Italian researchers developed combined plasma mode of continuous waves (CW) and pulsed (P) method in order to improve the efficiency and yield for the functional groups. This approach was used for the functionalization of POSS. The effect of the input power and duty cycle on the performance of plasma functionalization of octamethyl POSS was investigated and shows nitrogen-containing groups being successfully introduced on the POSS surface, and their cage structure was maintained after plasma treatment. While the results reported here are confined to one type of POSS derivative, the results provide a new platform to template POSS materials with a controllable degree of functionality using an environmentally-friendly, yet, effective methodology.
