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Small Molecule Diffusion in Semicrystalline Polymers

Alessandro Mattozzi, Mikael Hedenqvist, and Ulf Gedde. Dept. of Fibre and Polymer Technology, Royal Institute of Technology, Stockholm, Sweden

Diffusion of small molecules in semicrystalline polymers was studied by analyzing the different factors governing it. The variations in diffusion impedance due to changes in crystal morphology were calculated from morphological data and compared with n-hexane diffusion data. Mesoscale modeling was used to simulate the effect of crystal morphology on the diffusivity: an algorithm able to generate spherulite-like structures was developed and small molecule diffusion was simulated in the structures. The segmental mobility of the interfacial and of the amorphous component, assessed by solid-state 13C-NMR- spectroscopy, and the degree of molecular packing, determined by wide angle X-ray scattering, were measured for a series of poly(ethylene-co-octene)s after exposure to n-hexane and compared with the native materials. Atomistic simulations of n-hexane in amorphous poly(ethylene-co-octene) were used to study the penetrant dynamics within of the amorphous component.