Novel microgel-particle colloids: the detailed characterisation of the layer structure and chain topology of silica : poly(NIPAM) core-shell particles

A monodisperse core-shell microgel has been synthesised in which silica pro vides the core (average diameter 1367 Angstrom), and poly(NIPAM) the cross linked shell. Transmission Electron Microscopy and Photon Correlation Spect roscopy (PCS) measurements have confirmed the existence of a thick polymer layer. PCS measurements have shown that the hydrodynamic thickness of the l ayer is similar to 2450 Angstrom at 25 degrees C, collapsing to 600 Angstro m when heated to 70 degrees C. Small-angle neutron scattering (SANS) experi ments on the core-shell microgels show a high volume fraction near the surf ace and suggest an exponential volume fraction profile. PCS and SANS measur ements have also been used to measure the de-swelling of the layer with cha nge in temperature and the results are compared with classical microgel par ticles. (C) 2000 Elsevier Science Ltd. All rights reserved.