system
Given the following post, respond as if you're commenting on Reddit:
human
How does stickiness work? (xpost from /askreddit)

I've always been curious as to how glue and tape adhesive properties work, particularly the strong stuff, and glues that can hold even in water.
gpt
iorgfeflkd the unspellable summed it up pretty well, stickiness is the result of you having to break millions and millions of bonds all at once. However, some adhesives work by worming their way into cracks and pores on a surface, then hardening, which holds together something with mechanical force instead of chemical force.

To hold in water, a substance needs to be insoluble, or unable to be readily dissolved in water. Solubility in water is based on hydrogen bonding. While water is overall a neutral molecule, electrons like to hang out on the oxygen, leaving it slightly negative, and the hydrogens slightly positive. These partial charges can form weak bonds with other nearby charges, known as hydrogen bonds. Dissolving is the end result of many weak hydrogen bonds ripping apart stronger bonds. Molecules must have some kind of polarity to be soluble in water. Back to the original point, if a glue isn't a polar molecule, it'll hold in water.

Super glue, or cyanoacrylate, is a neat demonstration of all of the above. In general, it holds stuff together through mechanical force, by rapidly changing from a gel to a solid, though there is some degree of chemical bonding. Because most of its strength comes from mechanical force, it's not very good at holding nonporous substances together, as it can't get a very good hold on it.

Cyanoacrylate is a polar molecule, and is very much soluble in water - gluing something together at the bottom of a lake won't work. However, when you expose it to water, all the cyanoacrylates start forming strong bonds between each other, making long nonpolar cyanoacrylate chains. These chains make a solid substance that is insoluble in water.