IBM researchers, with collaborators at Stanford University, have
combined their expertise in porous materials for microprocessors and thin film
mechanical properties to study the fundamental properties of polymers under
Their challenge was to fill tiny holes called nanopores (1/10,000 the size of a
human hair) with long and bulky molecules. The equivalent of fitting a 300
passenger commercial plane into your car garage. While the latter is physically
impossible, polymers can deform to adapt to such a significant form factor
change. During this process, their intrinsic properties are dramatically
modified – which is precisely what our researchers were looking for. But the
results weren’t what they expected.
In their normal state (not confined), polymers' mechanical properties mainly
depend upon the number of entanglements (i.e, the number of knots). When you
pull on one chain, you pull on many knots such that a tremendous amount of
energy has to be dissipated before reaching a breaking point. This is what give
polymers their physical strength: from your plastic cup to your suitcase.
|Hybrid nanocomposite art|
by students at Stanford University
Think about trying to pull one noodle from a full plate of cooked pasta. It is
almost impossible to pull only one from the bunch. But if you could force all
the noodles into a tiny espresso cup, the knots would magically disappear because
it is the only way for the entangled pasta to accommodate such a small space.
Similarly in polymer physics, polymers' mechanical properties such as resistance
to fracture, decrease under confinement due to the loss of entanglements.
For the resulting nanocomposite materials, it was then predicted
that their mechanical properties would follow the same trend. Surprisingly, the
exact opposite is what IBM and Stanford researchers uncovered. The polymers’ resistance
to fracture increased with decreasing entanglements. The results showed that five
times more energy was required to break these nanocomposites as initially
The discovery has significant implications for the microelectronic industry as
microprocessors continue to shrink, and porous materials are widely used in
devices such as smartphones, and tablets due to their prominent insulating
properties. Its increased strength could help prevent mechanical failures of
the next generation of microprocessors when more porous materials, better
insulators but more fragile materials, are manufactured. This strategy is
currently under development at our Albany research and development center for
Read more about this breakthrough in the Nature Materials article Fundamental limits of material toughening in molecularly confined polymers.
Labels: Almaden, microprocessor, nanotechnology, polymer, Stanford