Interfacial dynamics of polydimethylsiloxane adsorbed on fumed metal oxide particles of a wide range of specific surface area

- Interfacial polymer fraction increases with specific surface area, S, of nanooxides.
- Interfacial dynamics and cooperativity are enhanced with increasing of surface roughness (S).
- Changes in interfacial polymer and overall dielectric response can be well described in terms of bimodal conformations.

Interfacial dynamics of polydimethylsiloxane adsorbed on silica and titania nanoparticles of a wide range of specific surface area (S, 25-342 m2/g) and size (8-80 nm in diameter for primary particles) was studied employing differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS). Both techniques revealed an increase of the interfacial polymer fraction with increasing of surface roughness S, accompanied with an enhancement of dynamics and cooperativity of the corresponding segmental relaxation (interfacial relaxation, αint). At the same time, bulk dynamics (glass transition temperature, Tg, and time scale of α relaxation) was not significantly affected. The results are discussed in terms of bimodal conformations of polymers adsorbed on solid surfaces and in terms of an increase of the apparent thickness of the interfacial layer with increasing of surface roughness.

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