Influence of octakis-functionalized polyhedral oligomeric silsesquioxanes on the physical properties of their polymer nanocomposites

We synthesized the polyhedral oligomeric silsesquioxane (POSS) derivatives octakis[dimethyl(phenethyl)siloxy]silsesquioxane (OS-POSS), octakis[dimethyl(4-acetoxy phenethyl)siloxy]silsesquioxane (OA-POSS), and octakis[dimethyl(4-hydroxyphenethyl)siloxy] silsesquioxane (OP-POSS) through hydrosilylation with octakis(dimethylsiloxy)silsesquioxane (Q₈M₈^H). To investigate the influence of these octuply functionalized POSS derivatives in polymer nanocomposites, we blended OP-POSS, OA-POSS, and OP-POSS with the homopolymer poly(ethylene oxide) (PEO) and characterized its resulting intermolecular interactions (e.g., hydroxyl-ether and carbonyl-ethylene oxide) using FTIR spectroscopy. The thermal properties of these blend systems were investigated using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The crystallization kinetics in the miscible binary blends of the crystalline polymer and these inorganic nanoparticles were also determined through DSC and optical microscopy (OM) analyses. Herein, we emphasize the effects of the functional groups on POSS nanocomposites on the crystallization kinetics of PEO. We found that OP-POSS/PEO blend had the highest thermal stability and lowest crystallization rate because its hydrogen bonding interactions (between its hydroxyl and ether units) were stronger than those (between carbonyl and methylene groups) in OA-POSS/PEO.