[AussieWog93]

From the article:

>The new material is a two-dimensional polymer that self-assembles into sheets, unlike all other polymers, which form one-dimensional, spaghetti-like chains. Until now, scientists had believed it was impossible to induce polymers to form 2D sheets.

ie: the existing polymers use 1D chains, not 3D.

[adrian_b]

The existing thermoplastic polymers use 1D chains.

The thermosetting polymers are initially synthesized as 1D chains, but after they are made into their intended form, the curing reaction cross-links all the 1D chains into a 3D network.

Because of its 3D structure, a cured thermosetting polymer can no longer be dissolved or melted. At high temperatures it will decompose or burn, instead of melting.

However, the thermosetting polymers, unlike covalent crystals like diamond, boron or silicon, have a 3D structure with big holes in it, so they are permeable to gases and other substances with small molecules.

The 2D polymer discussed in the parent article has a 2D structure similar to graphite sheets, i.e. a dense 2D lattice, without holes or pores.

This dense structure allows applications that cannot be done with traditional polymer coatings. This coating should be inpermeable like a glass, without being fragile.

The fact that it is light, as mentioned in the title, is pretty much irrelevant, because this is a material that is suitable only for coatings on objects made of other materials, not for the bulk material of an object.

[Karliss]

The article also said that one of biggest challenges with making 2D polymer was keeping it 2D without it going 3D. But there was no explanation why that would be worse.

[abracadaniel]

Normally the molecules can only assemble in a chain. They can make solids in three dimensions by being long and making a big tangled mess. It's like extruding dough into spaghetti, then stirring it around to make a big tangled ball. Instead, they found a way to roll the dough out into an arbitrarily large flat lasagna-like noodle. Then they stacked them and found they stick to each other well and could make a much stronger material than the spaghetti ball. The only real limit being the amount of dough and a space to roll it out on.