## 2 Materials and Methods  
3,4,5,6-Pentafluorostyrene (PPS) (Fluorochem, Hadfield, United Kingdom), poly(ethylene glycol) monomethyl ether (mPEG8, average \(M_{\rm{n}}\) = 350 Da) (Sigma-Aldrich, Darmstadt, Germany), and tin(II) 2-ethylhexanoate (Sn(EH)\({}_{2}\)) (Sigma-Aldrich, Darmstadt, Germany) were used as received. Anisole (Sigma-Aldrich, Darmstadt, Germany) was vacuum distilled over sodium, tetrahydrofuran (THF) (Sigma-Aldrich, Darmstadt, Germany) was refluxed over calcium hydride for 3 h and distilled under nitrogen, \(N\),\(N\),\(N^{\prime}\),\(N^{\prime\prime}\),\(N^{\prime\prime}\)-pentamethyldiethylenediamine (PMDTA) and (1-bromoethyl)benzene (1-BEB) (Sigma-Aldrich, Darmstadt, Germany) were vacuum distilled, and CuBr\({}_{2}\) (Sigma-Aldrich, Darmstadt, Germany) was recrystallized from a filtered aqueous solution. Solvents were purchased from Sigma-Aldrich (Darmstadt, Germany) and used as received. \({}^{1}\)H and \({}^{19}\)F nuclear magnetic resonance (NMR) measurements were carried out on a Bruker (Billerica, Massachusetts, MA, USA) Advance 400 (400 MHz) spectrometer with deuterated solvents (Sigma-Aldrich, Darmstadt, Germany) at room temperature. The sample concentration was approximately 30 g/L. For \({}^{19}\)F NMR chemical shift attribution, hexafluorobenzene was used as the internal standard, to which a chemical shift of \(-\)161.64 ppm is attributed in CDCl\({}_{3}\) compared to CFCl\({}_{3}\). For \({}^{1}\)H spectra the internal standard was the solvent peak. The number and weight average molecular weights (\(M_{\rm n}\), \(M_{\rm w}\)) were determined by gel permeation chromatography (GPC) using a Jasco (Hachioji-shi, Tokyo, Japan) PU-2089 Plus liquid chromatograph equipped with two PL gel 5 \(\upmu\)m mixed-D columns, a Jasco RI-2031 Plus refractive index detector, and a Jasco UV-2077 Plus UV/vis detector. Measurements were carried out using chloroform as the mobile phase at a flow rate of 1 mL/min and a temperature of 30 \({}^{\circ}\)C maintained by a Jasco CO 2063 Plus column thermostat. Polystyrene standards (Sigma-Aldrich Darmstadt, Germany) were used for calibration. The refractive index detector was used to obtain reported values. Samples were filtered with a 0.2 \(\upmu\)m polytetrafluoroethylene (PTFE) filter before injection. UV-Vis measurements were carried out using a Perkin-Elmer (Waltham, MA, USA) Lambda 650 and a Shimadzu (Kyoto, Japan) 2450 spectrometer. Samples were put into quartz cuvettes with a 10 mm optical path. Transmittance was measured at a fixed wavelength of 700 nm. The cloud point temperature (\(T_{\rm cp}\)) was defined as the temperature at which transmittance decreased to 50%. Aqueous solutions of the polymers at different concentrations (from 0.1 to 30 g/L) were tested. Measurements were taken at various temperatures, ranging from room temperature to higher than the \(T_{\rm cp}\) of the given substance. The temperature was varied manually using a thermostat. DLS measurements were carried out in polymer solutions with a Malvern (Malvern, Worcestershire, United Kingdom) Zetasizer Nano ZS particle analyzer (detection angle = 173\({}^{\circ}\)). Intensity, volume, and number distributions were obtained from the signal autocorrelation function through CONTIN analysis in the instrument software. Samples were prepared using high pressure liquid chromatography (HPLC)-grade water filtered through a 0.2 \(\upmu\)m cellulose acetate filter. After dissolving the chosen substance, the solution was then filtered through a 5 \(\upmu\)m cellulose acetate filter. At least 5 separate measurements were carried out for each solution. When all the results were coherent with each other, an average size distribution curve created by the instrument software was considered as an overall representative of the system. Reported hydrodynamic diameters are always calculated according to the intensity size distribution. To investigate the aggregation during the phase separation process, temperature-dependent DLS measurements were performed.