I mean on a molecular level, what about the surface of tape makes it adhesive?
In: Chemistry
It depends on the kind of tape, but AFAIK the adhesives used in tape – like most other adhesives such as glue or even just sticky things like paint – have to do two main things. The first thing they have to do is “wet” (or spread out all over) the substrate to which you’re trying to adhere, sort of like water, but more like a thin layer of play-doh or silly putty. It needs to get into all the nooks and crannies, and almost every material (even smooth glass!) has these at both macroscopic and microscopic levels.
The second thing adhesive has to do is resist getting pulled back out (water is only just OK at that), and the third thing it to do is resist getting broken apart from itself or separating from the tape strip. These two jobs are what make tape “stick,” and are sort of at odds with each other. There are different ways to make adhesive not want to separate from the substrate, including some crazy molecular-level interactions that are kind of like static electricity or magnets. That is a question for your next ELI5 though.
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