Fifth Floor- Solution Polymerization

If the temperatures required to melt the monomer are too high, or if bulk polymerization would be so exothermic as to be hazardous, you may wish to (or have to) use solution polymerization.

The solubility of a polymer decreases with increasing molecular weight and it is necessary to select a good solvent to dissolve the polymer. To select a good solvent, you may wish to compare the solubility parameter of your polymer to the solubility parameters of the available solvents. You may remember the expression "like dissolves like", and this relates to a molecule's cohesive energy density.

[Allcock-414] The Flory-Huggins interaction parameter,

, is the energy change that occurs when a mole of solvent molecules is removed from the pure solvent and immersed in an infinite amount of pure polymer.

There is an energy change in the removing the solvent from the the other solvent, and there is an energy change when this mole is solvent goes into the polymer.
In this scenario it could be said that the polymer dissolves the solvent.

The Flory-Rehner Equation is important too.

You may remember solution thermodynamics calculations from physical chemistry. They apply to the dissolving of a polymer in a solvent.

Last Update- July 4, 1995- wld