system
Given the following post, respond as if you're commenting on Reddit:
human
What in rubber's structure allows it to stretch?

What is natural rubber composed of on a molecular level that allows it to stretch?
gpt
There are a few things that give rubber some "stretchiness". Long molecular chains comprise the majority of elastic materials. However, long linear chains alone don't make something "stretchy". More often, they just make it viscous, like a bowl of spaghetti. However, adding a crosslinker, which connects long molecules together in sparse locations gives the bowl of spaghetti some rigid structure, making it less flowable, so it can return to some original state. But the crosslinking connections (added to rubbers via vulcanization, as an example) are sparse and sporadic which still allows the molecules to move enough to straighten when stretched, and coil/curl/deform when retracted.