Poly (N-isopropylacrylamide) microgel particles are found to form colloidal
crystals similar to those occurring in typical hard-sphere colloids like p
oly(methylmethacrylate) beads. Samples made of particles with different cro
sslinker concentrations are investigated and their deswelling ratio is dete
rmined using dynamic light scattering. Small-angle neutron scattering data
are also presented and analysed in terms of a face-centred-cubic crystal st
ructure. The characteristic length, a, of the elementary cell is found to b
e 535 +/- 16 and 495 +/- 15 nm for the two systems investigated. This leads
to particle radii of 189 +/- 6 and 175 +/- 5 nm, respectively. These value
s compare well to the radii determined using several different methods.