Single Molecule Study on Polymer-Nanoparticle Interactions: The Particle Shape Matters

The study on. the nanoparticle polymer interactions is very important for the design/preparation of high performance polymer nanocomposite. Here we present a method to quantify the polymer particle interaction at single molecule level by using AFM-based single molecille force spectroscopy (SMFS). As a proof-of concept study, we-choose poly-L-lysine (PLL). as the polymer and several different types of polyoxometa,lates (POM) as the model particles to construct several different polymer nanocomposites and to reveal the binding mode and quantify the binding strength in these systems. Our results reveal that the shape of the nanoparticle and the binding geometry in the composite have significantly influenced the P2 binding Strength of the PLL/POM complexes. Our dynamic force spectroscopy studies indicate that the disk-like geometry facilitate the rinbindirig of PLL/AtMo6,complexes in shearing mode, while the,mizipping mode becomes dominate in spherical PLL-P8W48 system. We have also systeinatically investigated the effects. of charge-numbers, particle size, and ionic strength-on the binding strength and binding mode Of PLL/POM,-respectively. Our results show that electroStatic interactions dominate the stability of PLL/POM complexes. These findings provide a way for tuning the Mechanical properties of polyelectrolyte nanoparticle composites: