Sprecher
Beschreibung
Literature dealing with polyelectrolyte (PE) chains with atomic/molecular compensating ions in solution is vast [1–3]. Studies of PE chains in the presence of charged colloids or nanoparticles (NPs)[4] are less common. Interesting recent examples include PE complexes with gold and silica NPs[3], forming coacervates, or precipitates, with potential applications in phase separation processes, including extraction and depollution[5]. Little research has focused on PE behavior in the presence of molecular colloids, of intermediate size between ions and colloids[6]. Polyhedral oligomeric silsesquioxanes (POSS) are molecular colloids with a size range of 1–3 nm, intermediate between ions and nanoparticles. Their interactions in solution can be tuned via the nature and length of pendant groups attached to the apices of a Si-O central cage. The compounds synthesized in the laboratory are a closed cage containing 8 silicon atoms and are stable in aqueous solution at a pH 2. The size of the Si-O cage was determined using the form factor and measures 0.8 nm. This tunability makes POSS ideal for studying their interactions in aqueous solution to form self-assemblies made of positively or negatively charged POSS with oppositely charged polyelectrolytes (PEs). We explore the POSS/PE assembly of Sodium Polystyrene Sulfonate ([-] charged PE) and primary amine-functionalized POSS. The mixtures form macroscopic aggregates and their structure is analyzed by small angle x-ray scattering (SAXS). The SAXS results obtained for POSS-PSS mixtures show a contribution from the POSS that depends on the [-]/[+] loading ratio. At a remarkable ratio close to 1, all the PSS seems to interact with all the POSS in solution, while at the other ration either PSS or POSS is in excess. Small angle neutron scattering (SANS) would be a technique of choice to identify the contribution and structure of each component using contrast matching. Using these methods, we investigate the influence of ionic strength, charge ratio to determine the key parameters the formation of complex POSS/PE architectures.