Discussion of unusually low dispersity in highly degraded LLDPE samples Samples of the LLDPE (Mw = 120 kg/mol, Ð = 2.5) that were heavily degraded due to hydrogenolysis, resulting in Mw < 5 kg/mol, displayed dispersities Ð = Mw/Mn < 1.5, which is significantly smaller than what is expected due to the random cleavage of CC backbone bonds, Ð ≈ 2. We speculate here on three possible reasons for this behavior.

Carbon nanotube aerogels are interesting platforms for the manufacture of lightweight composites. To guide the development, we screen with tight-binding atomistic calculations two primary crystalline organizations of nanotubes with 1.4−4.5 nm radii and 1−3 number of walls. Calculations reveal a crossover from polygonized nanotubes with hexagonal close-packing organizations to collapsed shapes organized in stacks. The energies of the two modes are captured into a concise form, which predicts the crossover radii and domains of their dominance. The graphite-like phase formed with collapsed nanotubes allows for ∼1 TPa Young's moduli. Bundles of collapsed nanotubes emerge as natural candidates for the developmnent of ultrastrong composites.