Plasticization effect of C60on the fast dynamics of polystyrene and related polymers: an incoherent neutron scattering study

We utilize inelastic incoherent neutron scattering (INS) to quantify how fullerenes affect the 'fast' molecular dynamics of a family of polystyrene related macromolecules. In particular, we prepared bulk nanocomposites of (hydrogenous and ring-deuterated) polystyrene and poly(4-methyl styrene) using a rapid precipitation method where the C 60 relative mass fraction ranged from 0% to 4%. Elastic window scan measurements, using a high resolution (0.9 µeV) backscattering spectrometer, are reported over a wide temperature range (2–450 K). Apparent Debye–Waller (DW) factors , characterizing the mean-square amplitude of proton displacements, are determined as a function of temperature, T . We find that the addition of C 60 to these polymers leads to a progressive increase in relative to the pure polymer value over the entire temperature range investigated, where the effect is larger for larger nanoparticle concentration. This general trend seems to indicate that the C 60 nanoparticles plasticize the fast (≈10 −15 s) local (≈1 Å) dynamics of these polymer glasses. Generally, we expect nanoparticle additives to affect polymer dynamics in a similar fashion to thin films in the sense that the high interfacial area may cause both a speeding up and slowing down of the glass state dynamics depending on the polymer–surface interaction.