Parts‐per‐million polyhedral oligomeric silsesquioxane loading induced mechanical reinforcement in polyethylene nanocomposites. When small and well‐dispersed yields big

The expectation that composites fabricated with nanoscale reinforcing materials will exhibit exceptional mechanical properties remains to be fulfilled. Here, octaisobutyl‐polyhedral oligomeric silsesquioxane (buPOSS) nanochemical was melt blended with low‐density/linear low‐density polyethylene (LDPE/LLDPE) to form nanostructured films. We demonstrate that buPOSS concentrations of only 80 to 400 parts‐per‐million (ppm) are enough to produce nearly 2‐fold increase of the film's tensile Young's modulus, E MD . Strikingly, there was no penalty on strain at fracture ε f,MD , as usually seen in reinforced (nano) composites, rather ε f,MD increased with buPOSS content. Furthermore, other important mechanical properties like toughness, yield stress, tear resistance, and dart impact strength were also an increasing function of buPOSS content. The dispersion of buPOSS into the polyethylene matrix at nearly single cage unit is the key to mechanical reinforcement. The buPOSS size D , smaller than the virtual tube diameter d t defined by Doi and Edwards, indicate that buPOSS is capable to intercalate the entangled macromolecules and mechanically reinforce without acting as stress concentrators. Furthermore, the entanglement intercalation and consequent reduction of free volume induced reduction of oxygen transmission (OTR) through the films and the barrier properties were intact after 18 months aging at room temperature. The nanosized and efficient dispersion of buPOSS is key to the mechanical reinforcement at only ppm loading and these results add a new paradigm to polymer nanocomposites formulation.