Partículas inteligentes de poli (nisopropilacrilamida), quitosana e poli (ácido acrílico): efeito da temperatura e do pH sobre suas propriedades em suspensões aquosas

摘要

The present study describes the stability and rheological behavior of suspensions ofpoly (N-isopropylacrylamide) (PNIPAM), poly (N-isopropylacrylamide)-chitosan (PNIPAMCS),and poly (N-isopropylacrylamide)-chitosan-poly (acrylic acid) (PNIPAM-CS-PAA)crosslinked particles sensitive to pH and temperature. These dual-sensitive materials weresimply obtained by one-pot method, via free-radical precipitation copolymerization withpotassium persulfate, using N,N -methylenebisacrylamide (MBA) as a crosslinking agent.Incorporation of the precursor materials into the chemical networks was confirmed byelementary analysis and infrared spectroscopy. The influence of external stimuli such as pHand temperature, or both, on particle behavior was investigated through rheologicalmeasurements, visual stability tests and analytical centrifugation. The PNIPAM-CS particlesshowed higher stability in acid and neutral media, whereas PNIPAM-CS-PAA particles weremore stable in neutral and alkaline media, both below and above the LCST of poly (Nisopropylacrylamide)(stability data). This is due to different interparticle interactions, as wellas those between the particles and the medium (also evidenced by rheological data), whichwere also influenced by the pH and temperature of the medium. Based on the results obtained,we found that the introduction of pH-sensitive polymers to crosslinked poly (Nisopropylacrylamide)particles not only produced dual-sensitive materials, but allowedparticle stability to be adjusted, making phase separation faster or slower, depending on thedesired application. Thus, it is possible to adapt the material to different media