  Large scale molecular dynamics simulations on polyvinyl alcohol were used to
investigate the distribution of unoccupied space under different heat
treatments. Representative volume elements consisting of 3600 chains of 300
monomers were equilibrated at melt state and cooled by different cooling rates.
The positions of center of mass of the monomers were extracted and a series of
spatial analysis were conducted to estimate the distribution of free volume or
unoccupied space by Voronoi tessellation algorithm. An open-source software was
employed which incorporates both compilers of Matlab and C programing languages
to reduce the computational costs associated with Voronoi calculations and
statistical analysis. The results confirmed that low free volume content is
achievable through annealing while high free volume content is achievable
through quenching samples at high cooling rates. An appreciable degree of
short-range order in the packing of chains is revealed in annealed samples.
