Re: What's the best way to explain polymers?

Aah yes, goopy stuff!. I guess the glue you used was white school glue; let's start with that. That's made with polyvinylalcohol (PVA), or maybe you used "latex glue". This sticky stuff is basically a latex suspension, that is a mixture of very small rubber particles in water (the usual odor of ammonia is real... it is there as a preservative). Both PVA and this natural particular rubber ("cis 1,4 polyisoprene" to be exact) are polymers (you probably guessed that from their chemical names). OK, so let's get down to the nitty gritty... what's a polymer? Ready for some Greek? Poly means many or much, and "mer" comes from meros meaning part. Just think of a polymer molecule as simply thousands (even millions) of the same building block molecule ("monomer") joined together. Maybe like those plastic beads young girls snap together to make bracelets and necklaces. Linear polymers like these glues are just as wiggly as that end-to-end bunch of beads. So what's up with the borax (sodium borate)? The borax is a "cross-linking" agent. It actually reacts with the rubber molecules forming bridges between strands of linear polymer. Now the rubber becomes more solid but can still flex... even spring back into shape - its not entirely rigid (these crosslinks are not too strong). Plus there's still a lot of water around when you make the goopy stuff and that gets caught up in the cross linked polymer.

Too much water (weak glue or the washable type) and the goopy stuff is slimey rather than "rubbery". You've probably heard of "vulcanization" of rubber. That's another method of crosslinking, normally using sulfur.

See also Could you please help me with molecule and polymer?
and Wha t holds rubber together?

Goopy wishes!