Polymer Nano-Materials Through Self-Assembly of Polymeric POSS Systems

Abstract

The self-organization of polyhedral silsesquioxane (POSS) moieties tethered as side groups onto flexible backbones of amorphous siloxanes and poly(1,2-butadiene) was investigated. For comparison, linear oligosiloxanes substituted with POSS units at the chain end (α- or α,ω-functionalization) were examined. The properties of POSS-functionalized materials were studied (SAXS, WAXD, DSC, TGA, and optical microscopy). The formation of organized POSS assemblies was monitored as a function of the structure of the polymer chain, as well as the POSS concentration in the polymer matrix. It was confirmed that the rubbery polymers allow the pendant POSS units to assemble without the competition of the main chain crystallization. Materials with a larger number of POSS groups tend to form lamellar structures. It was found that the process of disintegration of POSS assemblies in siloxanes is thermally driven. The temperature of melting depends on the structure of a POSS assembly, and the time needed for the organized structure recovery from the melt depends on the type of arrangement of POSS-moieties that is to be formed. At a low POSS content besides the POSS assemblies, which are crystallites of nanometric size, larger polycrystalline objects of micrometric sizes are formed. They consist of a greater number of POSS crystallites embedded in the siloxane polymer. Their shapes and sizes are dependent on the polymer structure and the history of the polymer sample.