Polyelectrolyte microgels based on poly-N-isopropylacrylamide:influence of charge density on microgel properties,binding of poly-diallyldimethylammonium chloride,and properties of polyelectrolyte complexes

摘要

The influence of the charge density of microgelsnon the binding of oppositely charged polyelectrolytes wasninvestigated. The charge density in the microgels wasnvaried via the amounts of charged comonomer (as e.g.,nmethacrylic acid) during microgel synthesis and also bynchanging the reaction conditions in order to influence thendistribution of the charged comonomer inside the poly-Nisopropylacrylamide-nco-methacrylic acid microgel. Thenvariation in charge density was monitored by takingnadvantage of the polyelectrolyte effect during acid–basentitration. Data of titrations of several microgels werenanalyzed by a modified Henderson–Hasselbalch equationnto monitor the influence of the charge density. Thenmicrogels contain either different amounts of cross-linkernbut same amounts of charged comonomer or the microgelsnwere synthesized with same amounts of cross-linker butndifferent functional monomers with different reactivitiesnyielding different spatial distributions. Charge density andnspatial distribution of charges in the microgel stronglyninfluence swelling and interaction with polyelectrolytes. Asnexpected, a highly charged microgel binds more polyelectrolytenthan a microgel with low amount of charged groups.nThe amount, however, does not only scale with the numbernof charges per microgel but also with the charge density ofnthe microgel. The lower the charge density of the microgel,nthe more polyelectrolyte per negative charge can bind. Innaddition, the charge density determines whether and at whichncomposition charge reversal of the microgel–polyelectrolytencomplexes occur.