Influence of Silane Coupling Agents on Filler Network Structure and Stress-Induced Particle Rearrangement in Elastomer Nanocomposites.

Filled rubber materials are key in many technologies having a broad impact on the economy and sustainability, the most obvious being tire technology. Adding filler dramatically improves the strength of rubber by reinforcement and tailoring the type of filler, and the chemistry of the interface between the filler and rubber matrix is important for optimizing performance metrics such as fuel efficiency. In a highly loaded, silica-filled, cross-linked model rubber closely mimicking commercial materials, both the filler network structure and the dynamics of the silica filler particles change when the silica surface is modified with silane coupling agents.

Subtle End Group Functionalization of Polymer Chains Drives Surface Depletion of Entire Polymer Chains.

The surface of a blend of 6 kDa polystyrene and 6 kDa polystyrene functionalized with hydroxymethyl ends not only is depleted of the higher energy end groups but also is depleted of any segments belonging to the functionalized chains. This is demonstrated using the emerging technique of surface layer matrix-assisted laser desorption ionization time-of-flight mass spectrometry (SL-MALDI-ToF-MS), which detects entire chains that have any repeat unit at the outer surface, and requires no labeling. Detecting entire chains provides information about the relationship of chain functionalization to surface segregation behavior of entire chains.

The hierarchy of environmental health and safety practices in the U.S. nanotechnology workplace.

Manufacturing of nanoscale materials (nanomaterials) is a major outcome of nanotechnology. However, the potential adverse human health effects of manufactured nanomaterial exposure are not yet fully understood, and exposures in humans are mostly uncharacterized. Appropriate exposure control strategies to protect workers are still being developed and evaluated, and regulatory approaches rely largely on industry self-regulation and self-reporting.