I recently made a shelf. (no, no images, it’s not up to the demands of my perfectionist tendencies, and I will not have your opinion of me lowered by substandard carpentry.) Back to the shelf. Due to the mediocrity of my fastening system, I needed to fill some gaps, Wood Putty to the rescue! The next morning I realized, what is that crap made of?

ooooohhhh. Acrylic. But what kind of polymer is that? Well, lots of kinds. Could be thermoplastic, could be thermoset; acrylic acid, or methacrylic acid. Options. The defining feature is that it is a resin (vague) and that its polymerization is precipitated by the application of heat and a initiator to the monomer (really vague). But… don’t worry there is a more specific answer to my query. 

It ends up that most acrylic in paint is Poly(methyl methacrylate) or PMMA. This is the clear glass-like plastic seen in products like Lucite® and Plexiglas®. Once dried it gives that hard solid finish desirable in paints, or wood fillers. Interestingly PMMA is hydrophobic and hence water insoluble. (But the package says cleans with water!?) In this case a co-polymer is used, to suspend the PMMA in water, poly(vinyl alcohol-co-vinyl acetate. Just like lipids this polymer has hydrophobic and hydrophilic groups; in-order to satisfy both halves of its “personality” the vinyl co-polymer loops into a circle with the phobic acetate groups facing in and the phillic alcohol groups facing out. This shape leaves a nice dry center for the PMMA to hide from the water in. It is by this means that insoluble groups are suspended in water based materials. This wrapping of a molecule by a second molecule, for the goal of suspension, is termed a latex; hence latex paints. (Latex fun fact by the fine folks at the Macrogalleria)