PEGylated NiPAM microgels: synthesis, characterization and colloidal stability. Issue 5 (17th January 2019) - Es Sayed, Julien
Abstract : The incorporation of hydrophilic PEG chains into the synthesis of thermoresponsive NiPAM microgels allows size-controlled and monodisperse microgels with both a constant VPTT and a high colloidal stability to be obtained. Abstract : The objective of this work is to synthesize highly stable thermoresponsive microgels that could be used in diverse applications. To achieve this, N -isopropylacrylamide (NiPAM) based microgels were first synthesized by surfactant-free precipitation polymerization of NiPAM in the presence of poly(ethylene glycol)methacrylate (PEG) as a macro-comonomer and methylenebisacrylamide (MBA) as a chemical crosslinker. By combining a complete set of techniques such as dynamic light scattering (DLS), scanning electron microscopy (SEM), zetametry, 1 H NMR and micro-differential scanning calorimetry (μDSC), we clearly demonstrate that (i) the incorporation of the PEG chains controls the size and the polydispersity of the NiPAM-based microgels, whereas the thermal behavior in solution (enthalpy, volume phase transition temperature (VPTT)) remains almost the same as for pure NiPAM microgels; (ii) the PEG chains are mainly located on the microgel periphery; and (iii) the presence of the PEG chains strongly increases the colloidal stability of microgels in electrolyte solutions at high temperatures.