Sonochemical synthesis and characterisation of thermoresponsive microgel particles

Thermoresponsive microgel particles of N-isopropylmethacrylamide and N,N′-methylenebisacrylamide were sonochemically synthesised in water containing sodium dodecylsulfate. Fluorescence spectroscopic measurements using the probes, pyrene and 1-pyrene-carboxaldehyde, showed that microgel systems with a higher crosslinker (N,N′-methylenebisacrylamide) percentage had a more rigid structure. It was also found that a higher crosslinker percentage gave a more hydrophobic surface with a greater density of crosslinking whereas a lower crosslinker percentage gave microgel particles with polymer chains extending out from the surface. Electrophoretic mobility measurements indicated that the microgel particles were electrokinetically unstable since the surface layer of the particles only possessed a low charge (reflective of potentials <|25| mV). However, the majority of the systems were sterically stabilised.

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► Thermosensitive microgel particles of N-isopropylmethacrylamide and N,N′-methylenebisacrylamide were successfully synthesized by sonochemical means.
► It was found that the conversion percentage depended on the reaction temperature with a lower conversion for microgel systems synthesised at a higher temperature.
► The study also showed that only microgel systems synthesised at the higher temperatures were monodisperse and that the hydrodynamic diameter of the microgel particles increased with reaction temperature and crosslinker percentage.
► Fluorescence spectroscopy measurements using the probes pyrene and pyrene carboxaldehyde showed that microgel systems with a higher crosslinker percentage possessed a more rigid structure.
► These microgels have potential applications in drug delivery procedures.