Observation of Concentration Fluctuations in Polymer Gels Performed by Neutron Spin Echo

Abstract

We applied these methods of small-angle neutron scattering (SANS) and neutron spin echo (NSE) on a swollen poly (N-isopropyl acrylamide) (NIPA) gel in order to observe the elastic scattering of frozen concentration fluctuations due to crosslinks. We successfully obtained the structure factor for the frozen concentration fluctuations in a q-domain of q > 0.01 A⁻¹ while in a q-domain of q < 0.01 A⁻¹; this attempt failed due to the limited performance of the q-resolution and the Fourier time tF of the current specifications of the NSE spectrometers. This technical hurdle for the spectrometer should be overcome on an intensified neutron source for the next generation, realizing t_F of µs-order and the q-resolution down closer to 0.001 A⁻¹.