Localized and Collective Dynamics in Liquid-like Polyethylenimine-Based Nanoparticle Organic Hybrid Materials

Broadband dielectric spectroscopy, rheology, and nuclear magnetic resonance spectroscopy are employed to study molecular dynamics in a nanoparticle organic hybrid material (NOHMs) system comprising 20 wt % silica nanoparticles ionically bonded to a polyethylenimine canopy. By comparing the neat polymer (used as a canopy) to the derivative NOHMs, we find that timescales characterizing segmental dynamics in the NOHM are identical to those for the neat polymer. Detailed analysis of the carbon-spin lattice relaxation times yields mechanistic insights into localized and collective dynamics, in quantitative agreement with dielectric results. Interestingly, the NOHMs retain liquid-like characteristics unlike conventional polymer nanocomposites but exhibit higher viscosity due to additional contributions from tethered polymer chains and mesoscopic structuring. These findings demonstrate the potential of achieving unique and desired material properties via NOHMs by an informed choice of the canopy material.

Automated summary

Broadband dielectric spectroscopy, rheology, and nuclear magnetic resonance spectroscopy were used to study molecular dynamics in a nanoparticle organic hybrid material (NOHMs) system with 20 wt % silica nanoparticles ionically bonded to a polyethylenimine canopy. The timescales characterizing segmental dynamics in the NOHM were found to be the same as those for the neat polymer canopy. Detailed analysis of carbon-spin lattice relaxation times provided mechanistic insights into localized and collective dynamics, in agreement with dielectric results. The NOHMs exhibited liquid-like characteristics but had higher viscosity due to contributions from tethered polymer chains and mesoscopic structuring.