Surface Modification of Thermoresponsive Microgels via Layer-by-Layer Assembly of Polyelectrolyte Multilayers

This study describes the layer-by-layer (LbL) assembly of polyelectrolyte multilayers of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(styrenesulfonate) (PSS) on soft and porous supports as provided by the entangled mesh network of poly(

N

-isopropylacrylamide) (PNiPAM) microgels with varying thermoresponsive core and core-shell structures. Dynamic light scattering was used to follow the build-up of the PDADMAC/PSS multilayer assembly on thermoresponsive microgel particles and electrophoresis measurements were used to confirm charge reversal after each layer deposition. We demonstrate an “odd-even” effect of the size of the coated microgel depending on the type of polyelectrolytes in the outermost layer. We also show that a priming layer of polyethyleneimine (PEI) causes drastic surface modification of the microgel, but that on subsequent adsorption of the next layer (PSS) the thermoresponsive behavior of the native microgel can be recovered. Similarities and differences to LbL assembly of polyelectrolyte multilayers on hard and rigid supports will be discussed.