Structure and polymer dynamics within PNIPAM-based microgel particles

• SANS demonstrated that PNIPAM microgels present a core–shell structure.
• Incoherent neutron scattering permits us to study collective dynamics of microgel chains.
• The polymer dynamics investigated by DOSY-NMR complements the results of neutron scattering.
• The dynamics of water within microgels was studied by solvent relaxation NMR.

The synthesis of temperature-responsive microgels of poly(N-isopropylacrylamide) (PNIPAM) was first reported in 1986 and, since then, there have been hundreds of publications describing the preparation, characterization and applications of these systems. This paper reviews the developments concerning the study of the structure of PNIPAM-based microgels performed over the last years using small angle neutron scattering (SANS) and also the investigations of the polymer-chain dynamics within the microgels carried out with incoherent elastic and quasielastic neutron scattering, and pulse field gradient nuclear magnetic resonance (PFG-NMR) techniques. Furthermore, the self-diffusion coefficient of the water molecules within the microgel, determined by means of solvent relaxation NMR, is also discussed as a function of the polymer volume fraction of the microgels.

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