## 2 Sample Environment Components
### Light Scattering  
Dynamic light scattering is a well established method for the characterization of particles in suspension by probing their diffusive behavior [38]. For the dynamic light scattering setup inspired by [36; 37], the light scattering plane is inclined by 20\({}^{\circ}\) relative to the SANS plane, to prevent problems arising from reflections on the cuvettes. A scheme of the optical setup can be found in Figure 3.  
The laser light (633 nm, 21 mW, HNL210L-EC, Thorlabs, Newton, NJ, USA) passes a shutter (SH05/M, Thorlabs, Newton, NJ, USA) and a filter wheel (FW212C, Thorlabs, Newton, NJ, USA) equipped with neutral density filters with optical densities of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 1.0, 1.3, 2.0 and 3.0 and is coupled into a polarization-maintaining single mode fiber (P3-630 PM-FC-1, Thorlabs, Newton, NJ, USA) with a fiber port (PAF-X-5-A, Thorlabs, Newton, NJ, USA). The laser light is emitted from a fiber collimator (60 FC-4-M5-33, Schafter and Kirchhoff, Hamburg, Germany) and focused onto the sample through a Glan-Thompson polarizer (GTH10M-A, Thorlabs, Newton, NJ, USA). After passing another Glan-Thompson polarizer and a laser line filter (FL632.8-1, Thorlabs, Newton, NJ, USA) the light scattered by the sample is collected by the same collimator type and coupled into a single mode optical fiber (630 HP with FC/PC and FC/APC connectors, Thorlabs, Newton, NJ, USA). For the detection in pseudo-cross configuration, a fiber optic beam splitter (ALV, Langen, Germany) is used to split the scattered light in a ratio of about 50:50. Afterwards, the light is detected into two single photon counting modules (SPCM-AQRH-14-FC, Excelitas Technologies, Waltham, MA, USA). For correlation, a field programmable gate array board (Spartan-6 FPGA, Xilinx, San Jose, CA, USA) is programmed analogously to a previous implementation for fluorescence correlation spectroscopy [39]. For the alignment of the setup, at first the incident laser beam is focused on the sample position. Then, an auxiliary laser is coupled into the fiber couplers of the detection side, to enable a prealignment by eye. After that, the detection can be easily adjusted to maximum scattered intensity and the quality of the correlation function. The sample environment for in situ dynamic light scattering and SANS measurements is equipped with two parallel setups for measuring dynamic light scattering at two different scattering angles \(\theta\) of approximately 120\({}^{\circ}\) and 71\({}^{\circ}\). Due to refraction on the cuvette-air and cuvette-solvent interfaces, the precise scattering angle is calculated using the refractive index \(n\) of the solvent according to [PERSON]'s law for each temperature. To validate the correct operation of the dynamic light scattering setup, polystyrene standard spheres with a radius of 25 nm and 200 nm were measured. Figure 4 shows a autocorrelation function and the respective cumulant fit for each angle of measurement as an example. Here, sound autocorrelation functions with an intercept of about 1 indicate a well-adjusted light scattering setup. The measurement of an autocorrelation function is completed within 30 s. This enables multiple DLS experiments within the duration of a SANS experiment (some 10 min) and therefore the in situ monitoring of the sample stability. Figure 3: Scheme of the instrument components required for light scattering and the resulting beampath. The relaxations rates \(\Gamma\) received from the fit can be converted into the translational diffusion coefficient \(D_{T}\) with the magnitude of the scattering vector \(q=\frac{4\pi m}{\lambda}\sin(\frac{\Theta}{2})\). Here, \(\lambda\) is the wavelength, \(\Theta\) is the scattering angle and \(n\) is the refractive index of the solvent.