# Density of a dye

1. Feb 27, 2005

I'm trying to figure out the number density (molecules/unit volume) of the dye for a sample of dye doped PMMA. The information I have is that the dye makes up 1% by weight of the mixture used to make the sample. I also have the chemical structure of the dye. I looked up the structure of the PMMA and found it here: http://www.psrc.usm.edu/macrog/pmma.htm [Broken], but I don't understand what the brackets around the $$CH_2-C$$ group signify.

Last edited by a moderator: May 1, 2017
2. Feb 27, 2005

### Staff: Mentor

The diagram of the molecule shows the unit molecule or monomer - methyl methacrylate. PMMA, or poly-methyl methacrylate, is a polymerized structure. Presumably, they could not make the brackets large enough in that example.

For the molecular mass, try using MM of methyl methacrylate monomer, which has 2 less hydrogen atoms than the MMA molecule, because in the polymer, these sites bond with other carbon atoms in the adjacent MMA molecules.

Last edited: Feb 27, 2005