5982
Macromolecules 2000, 33, 5982-5987
Atomistic Dynamics of Nanoscale Polymer Particles Kazuhiko Fukui, Bobby G. Sumpter, Michael D. Barnes, and Donald W. Noid* Chemical and Analytical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6197 Received January 11, 2000; Revised Manuscript Received May 31, 2000
ABSTRACT: Full classical molecular dynamics was used to study the atomistic details of nanometer scale polymer particles. Using a previously developed efficient molecular dynamics-based method for the generation of polymeric nanoparticles, we model polyethylene (PE) with up to 120 000 atoms, poly(ethylproplyene) (PEP), atactic polypropylene (aPP), and polyisobutylene (PIB) with up to 12 000 backbone atoms. A variety of characteristics and thermodynamical properties of those nanoscale particles are obtained to interpret the properties of a fine polymer particle distinguished from the bulk solid phase. The molecular volume and total energy as a function of temperature are calculated to predict the melting point, glass transition temperature, and heat capacity for the nanoscale particles.
I. Introduction A recent technology based on microdroplet stream techniques was developed for creating monodisperse polymer particles of arbitrary composition and size from solution.1-3 This method can be used to produce polymer nano- and microparticles that can be made as small as ∼200 nm with size dispersion of about 1-2%. The refractive index obtained from the data analysis of the particles is consistent with bulk values, and the level of agreement indicates that the particles are nearly perfect spheres. With this technique, homogeneous polymer blend microparticles was also generated from bulk-immiscibe polymer components in solution. For small droplets of solution (
