Small-angle neutron scattering

The measurements have been performed using two SANS instruments, SANS-I at the Paul Scherrer Institut (Villigen, Switzerland) and D11 at the Institut Laue-Langevin (Grenoble, France). SANS-I has been operated using a neutron wavelength λ = 1.1 nm for the sample-to-detector distance d_SD = 18 m, and a λ = 0.5 nm for d_SD = 6 m. D11 has been operated at a constant λ = 0.6 nm for d_SD = 28, 5.5, and 1.7 m. SANS-I has a ³He detector with a pixel size of 7.5 mm by 7.5 mm. While D11 has Stokes multitube arrays with pixels of 4 mm by 8 mm. The error in wavelength selection is Δλ/λ = 10%. All measurements were performed at a constant temperature of (20.0 ± 0.1)°C.

All the suspensions were prepared in pure D₂O to contrast-match the scattering length density of the d_83%PEG and the solvent. In this way, the contribution to the scattering signal of d_83%PEG is masked and the scattered intensity depends only on the size and internal architecture of the hydrogenated nanogels in solution. A similar approach that uses deuterated nanogels instead of d_83%PEG to create an “invisible” matrix with a few interspersed hydrogenated nanogels that are embedded has been largely used to access the response of nanogels with different internal architecture and sizes to crowding (2, 48). These nanogels come from the same batches of the nanogels used in the literature (19, 49, 50). More information about the precipitation polymerization synthesis can be found in section S2 and in (19, 49, 50).