Mixing poly(ethylene glycol) (PEG) solutions with aqueous dispersions of clay platelets (Laponite) results in the formation of nanocomposite hydrogels. NMR spectroscopy was used to probe the evolution of the PEG local dynamics during gelation: these NMR measurements led to the description of the chain ordering induced by the clay layer assembling. These experiments also pointed out a significant slowing-down of the PEG chain motions close to the platelets.The segmental dynamics of these interfacial PEG chains was then investigated through solid-state NMR. While such chain portions are �frozen� on the tens of nanoseconds time scale, PEG segmental motions were detected over several tens of microseconds. Such motions are highly restricted since at room temperature, their frequencies were found to be similar to the ones displayed by bulk  amorphized PEG chains, considered 10 K below. Complementary 2H NMR experiments enabled to precise the geometry of these reorientational motions.

Surface-induced ordering and interfacial dynamics in nanocomposite polymer-based hydrogels: A solid-state NMR investigation

245th National Meeting (2013)

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