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Title: Local structure of temperature and pH-sensitive colloidal microgels

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:
; ;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5]
  1. Dipartimento di Scienze, Sezione di Nanoscienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma (Italy)
  2. 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)
  3. Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, Via G. Moruzzi 1, I-56124 Pisa (Italy)
  4. Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via G. Moruzzi 3, I-56126 Pisa (Italy)
  5. ISIS-STFC, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX (United Kingdom)
Publication Date:
OSTI Identifier:
22489626
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 11; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CONCENTRATION RATIO; CONTROL; NEUTRON DIFFRACTION; PARTICLE STRUCTURE; PARTICLES; PH VALUE; PHASE TRANSFORMATIONS; POLYMERS; POROUS MATERIALS; SMALL ANGLE SCATTERING; SOLIDS; TEMPERATURE DEPENDENCE; WATER