Exploration on structure and stability of polypropylene during heating and cooling processes in terms of molecular dynamics simulations

Polymer materials are widely applied as drug solid dispersion reagents. The exploration and investigation on the structure and stability of different phases of polypropylene (PP) are very important and challenging, which will be very helpful for understanding of the reason why drug solid dispersion reagents can stabilize the drugs. In this work, the structure, thermodynamic and kinetic behaviors of PP polymers with different chain length during heating and cooling processes are examined and investigated based on molecular dynamics simulations. The simulated glass transition temperatures of the PP polymers are in agreement with experimental values. The amorphous PP1000–PP3000 exhibit higher stability than their crystalline states, but it is not the case for PP4000. Results reveal that the two important factors, that is, large entropy and relatively low molecular mobility lead to the high stability of amorphous PP1000–PP3000.