Density Measurements of Annealed Amorphous Polymers

The flotation method of the density measurement was adapted to reach sufficient accuracy with which the differences due to annealing amorphous polymers above their glass transition temperature can be traced. The densities of amorphous poly(methyl methacrylate) and polystyrene increase logarithmically in the course of the annealing, which suggests that some arrangement or ordering takes place. However, the changes are not stable.