title: Local structure of temperature and pH-sensitive colloidal microgels.
abstract: The temperature dependence of the local intra-particle structure of colloidal microgel particles, composed of interpenetrated polymer networks, has been investigated by small-angle neutron scattering at different pH and concentrations, in the range (299÷315) K, where a volume phase transition from a swollen to a shrunken state takes place. Data are well described by a theoretical model that takes into account the presence of both interpenetrated polymer networks and cross-linkers. Two different behaviors are found across the volume phase transition. At neutral pH and T ≈ 307 K, a sharp change of the local structure from a water rich open inhomogeneous interpenetrated polymer network to a homogeneous porous solid-like structure after expelling water is observed. Differently, at acidic pH, the local structure changes almost continuously. These findings demonstrate that a fine control of the pH of the system allows to tune the sharpness of the volume-phase transition.
authors.affiliation: Dipartimento di Scienze, Sezione di Nanoscienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Nigro
authors.affiliation: Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR) UOS Sapienza and Dipartimento di Fisica, Sapienza Università, Pz.le Aldo Moro 5, I-00185 Roma, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Angelini
authors.affiliation: Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, Via G. Moruzzi 1, I-56124 Pisa, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Bertoldo
authors.affiliation: Dipartimento di Scienze, Sezione di Nanoscienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Bruni
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via G. Moruzzi 3, I-56126 Pisa, Italy.
authors.forename: Valter
authors.initials: V
authors.lastname: Castelvetro
authors.affiliation: Dipartimento di Scienze, Sezione di Nanoscienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy.
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Ricci
authors.affiliation: ISIS-STFC, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, United Kingdom.
authors.forename: Sarah
authors.initials: S
authors.lastname: Rogers
authors.affiliation: Istituto dei Sistemi Complessi del Consiglio Nazionale delle Ricerche (ISC-CNR) UOS Sapienza and Dipartimento di Fisica, Sapienza Università, Pz.le Aldo Moro 5, I-00185 Roma, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Ruzicka