A polymer-diluent model exhibiting antiplasticization has beendeveloped and characterized by molecular dynamics simulations. Antiplasticizer molecules are shown to decrease the glass transition temperature Tg, but to increase the elastic moduli of the polymeric material. The addition of antiplasticizing particles renders the polymer melt a stronger glass-forming material through various characteristic temperatures, the fragility parameter D from fits to the VFTH equation, and through the observation of the temperature dependence of the size of cooperatively rearranging regions (strings) in each system. The length of the strings exhibits a weaker temperature dependence in the antiplasticized glass-forming system than in the more fragile pure polymer, consistent with the Adam-Gibbs model of glass formation.Upon cooling, the strings become increasingly concentrated in the antiplasticizer particles. Finally, we discuss several structuralindicators of cooperative dynamics, and find that that the dynamic propensity gives a strong correlation with the mobility in eachsystem.
Citation: Journal of Chemical Physics
Pub Type: Journals
antiplasticer additives, film imprinting, fragility, glass transition, nanoparticles, polymer melt, shear modulus, voronoi volume