Valentina Nigro1, Roberta Angelini2, Benedetta Rosi3, Monica Bertoldo4, Elena Buratti4, Stefano Casciardi5, Simona Sennato6, Barbara Ruzicka7. 1. Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), sede Sapienza, Pz.le Aldo Moro 5, I-00185 Roma, Italy; Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy. Electronic address: valentina.nigro@uniroma1.it. 2. Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), sede Sapienza, Pz.le Aldo Moro 5, I-00185 Roma, Italy; Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy. Electronic address: roberta.angelini@cnr.it. 3. Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy. 4. Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, Via G.Moruzzi 1, I-56124 Pisa, Italy. 5. Department of Occupational and Environmental Medicine, Epidemiology and Hygiene, National Institution for Insurance Against Accidents at Work (INAIL Research), Via Fontana Candida 1, Monte Porzio Catone, 00040 Rome, Italy. 6. Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), sede Sapienza, Pz.le Aldo Moro 5, I-00185 Roma, Italy; Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy. 7. Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR), sede Sapienza, Pz.le Aldo Moro 5, I-00185 Roma, Italy; Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy. Electronic address: barbara.ruzicka@cnr.it.
Abstract
HYPOTHESIS: The peculiar swelling behaviour of poly(N-isopropylacrylamide) (PNIPAM)4-based responsive microgels provides the possibility to tune both softness and volume fraction with temperature, making these systems of great interest for technological applications and theoretical implications. Their intriguing phase diagram can be even more complex if poly(acrylic acid) (PAAc)5 is interpenetrated within PNIPAM network to form Interpenetrating Polymer Network (IPN)6 microgels that exhibit an additional pH-sensitivity. The effect of the PAAc/PNIPAM polymeric ratio on both swelling capability and dynamics is still matter of investigation. EXPERIMENTS: Here we investigate the role of PAAc in the behaviour of IPN microgels across the volume phase transition through dynamic light scattering (DLS),7 transmission electron microscopy (TEM)8 and electrophoretic measurements as a function of microgel concentration and pH. FINDINGS: Our results highlight that aggregation is favored at increasing weight concentration, PAAc content and pH and that a crossover PAAc content CPAAc∗9 exists above which the ionic charges on the microgel become relevant. Moreover we show that the softness of IPN microgels can be tuned ad hoc by changing the PAAc/PNIPAM ratio. These findings provide new insights into the possibility to control experimentally aggregation properties, charge and softness of IPN microgels by varying PAAc content.
HYPOTHESIS: The peculiar swelling behaviour of poly(N-isopropylacrylamide) (PNIPAM)4-based responsive microgels provides the possibility to tune both softness and volume fraction with temperature, making these systems of great interest for technological applications and theoretical implications. Their intriguing phase diagram can be even more complex if poly(acrylic acid) (PAAc)5 is interpenetrated within PNIPAM network to form Interpenetrating Polymer Network (IPN)6 microgels that exhibit an additional pH-sensitivity. The effect of the PAAc/PNIPAM polymeric ratio on both swelling capability and dynamics is still matter of investigation. EXPERIMENTS: Here we investigate the role of PAAc in the behaviour of IPN microgels across the volume phase transition through dynamic light scattering (DLS),7 transmission electron microscopy (TEM)8 and electrophoretic measurements as a function of microgel concentration and pH. FINDINGS: Our results highlight that aggregation is favored at increasing weight concentration, PAAc content and pH and that a crossover PAAc content CPAAc∗9 exists above which the ionic charges on the microgel become relevant. Moreover we show that the softness of IPN microgels can be tuned ad hoc by changing the PAAc/PNIPAM ratio. These findings provide new insights into the possibility to control experimentally aggregation properties, charge and softness of IPN microgels by varying PAAc content.
Authors: Elena Yu Kozhunova; Galina A Komarova; Oxana V Vyshivannaya; Irina R Nasimova; Anastasia E Kuvarina; Vera S Sadykova Journal: Int J Mol Sci Date: 2022-04-15 Impact factor: 6.208