Defined Complexes of Negatively Charged Multisensitive Poly(N-isopropylacrylamide-co-methacrylic acid) Microgels and Poly(diallydimethylammonium chloride)

Abstract

The influence of poly(diallyldimethylammonium chloride) (PDADMAC) on pH-and temperaturesensitive negatively charged microgels was investigated with regards to different ratios between positive charges having their origin in PDADMAC and negative charges resulting from copolymerization of N-isopropylacrylamide (NiPAM) with methaacrylic acid (MAA). The concentration of the PDADMAC solution (regarding to monomeric units) was determined by argentometric and polyelectrolyte titration, the amount of MAA in the microgel was characterized with conductometric titration. The composition of the complexes between microgel and PDADMAC was available by centrifugation of the mixture and comparing the PDADMAC concentration in the supernatant with the initial concentration. Different from many other systems, we observed no flocculation at any microgel and PDADMAC ratio, but stable complexes were obtained. Because of the softness of a microgel in contrast to rigid particles, the microgel properties are strongly altered by the polyelectrolyte. Consequently, size, ζ-potential as well as the pH and temperature sensitivity of the microgel-polyelectrolyte complexes can be influenced by the adsorbed polyelectrolyte. Thus, polyelectrolyte adsorption allows tailoring the behavior of "smart" environmentally sensitive microgels.

Interaction between lysozyme and colloidal poly(NIPAM-co-acrylic acid) microgels

“…At high charge ratios binding also becomes influenced by excluded volume interactions (the protein volume fraction is estimated to be 0.2-0.3 at b = 1). Again it is interesting to note that Kleinen and Richtering clearly observed ''charge reversal" when the polycation charges were in excess over the microgel charges in the mixtures [42]. A possible explanation to this is that the polycation only partially penetrates into the network, so that the binding resembles adsorption more than absorption, as pointed out by these authors.…”

“…In particular, this work investigates how the binding of lysozyme affects the microgel size and electrophoretic mobility, and how these properties correlate with the colloidal stability of the microgel dispersion. Similar aspects have recently been investigated for mixtures of linear polyelectrolytes and oppositely charged colloidal poly(NIPAM-co-methacrylic acid) microgels [42].…”

“…The relatively large negative surface charge of the microgels shows that the effect is not simply due to neutralization of the surface regions of the microgels, but instead caused by fairly strong attractive forces between the microgels. Interestingly, recently Kleinen and Richtering reported that the binding of the linear polycation PDADMAC did not, in general, lead to precipitation of poly(NIPAM-co-methacrylic acid) microgels [42]. The reason for this discrepancy is not clear, but can possibly be due to the very low ionic strength in their study, leading to strong electric double layer repulsions.…”

“…The interaction between microgels and oppositely charged surfactants [29][30][31][32][33][34][35], polypeptides [36][37][38][39][40][41], and linear polyions [42] have been studied in some detail, and there are features in common with microgel-protein interactions, such as the importance of electrostatic interactions and the frequent appearance of core/ shell structures. For proteins, the latter phenomenon was first reported for the uptake into oppositely charged macrogels [17,19].…”

Microgels by Precipitation Polymerization: Synthesis, Characterization, and Functionalization

“…The layer-by-layer technique was used by the same group to design complex microgel colloids (Fig. 18) [118].…”