Everyday physics - polymers - Part 1

 The science of polymers is claimed by chemists, but I'm going to yank that control away and bring it to physics.  They can cry if they want to.

A polymer starts as a monomer, which can be a very long molecule.  You create a monomer in a vat with chemistry.  The main property is very active end points and not much chemical activity along the sides.  For physics, we think of the activity as charges, so that we have high charges (forces) at the ends, and none along the sides.

So, it is basically a single strand of spaghetti, and you can mix (create) it as a batch of cooked spag in water.  In the water, it is a slinky, slimy mess.

We now deal with polymers all the time, and they have replaced many other things.  I have particular fun with polymer paint for the cottage.  The stains and paints used to be pigments in oil solvents, now they are all polymers in water.  This has caused a lot of problems

If the spag dries on that plate, it becomes a solid hunk.  The strength of the hunk is dependent on the 'cross-links' and strength of the strands.  The cross-links glue strand to strand where they cross.  A good paint polymer is easy to spread when wet, and the cross-links develop as it cures, or dries.  I also use a lot of epoxy, which doesn't use water.

The important physics for the cottage is the adhesion of the paint to the surface.  You can have a very strong polymer with long chains, and glue that only sticks strand to strand.  I've painted a polymer on the deck of the cottage, and next year it comes off in sheets, which are very strong.  Not useful.

So, I've had to play a game of long and short polymers. 

-to be continued