  Amorphous solids, which show characteristic differences from crystals, are
common in daily usage. Glasses, gels, and polymers are familiar examples, and
polymers are particularly important in terms of their role in construction and
crafting. Previous studies have mainly focused on the bulk properties of
polymeric products, and the local properties are less discussed. Here, we
designed a distinctive protocol using the negatively charged nitrogen vacancy
center in nanodiamond to study properties inside polymeric products in situ.
Choosing the curing of poly dimethylsiloxane and the polymerization of
cyanoacrylate as subjects of investigation, we measured the time dependence of
local pressure and strain in the materials during the chemical processes. From
the measurements, we were able to probe the local shear stress inside the two
polymeric substances in situ. By regarding the surprisingly large shear stress
as the internal tension, we attempted to provide a microscopic explanation for
the ultimate tensile strength of a bulk solid. Our current methodology is
applicable to any kind of transparent amorphous solids with the stress in the
order of MPa and to the study of in situ properties in nanoscale. With better
apparatus, we expect the limit can be pushed to sub-MPa scale.
