## 2 Experimental Section  
### Instrumentation  
Standard SEC was performed with THF as the mobile phase (flow rate 1 mL min\({}^{-1}\)) on a SDV column set from PSS (SDV 1000, SDV 100000, SDV 1000000) at 30 \({}^{\circ}\)C. Calibration was carried out using PS standards (from Polymer Standard Service, Mainz). For the SEC-MALLS experiments, a system composed of a Waters 515 pump (Waters, Milford, CT), a TSP AS100 autosampler, a Waters column oven, a Waters 486 UV detector operating at 254 nm, a Waters 410 RI-detector and a DAWN DSP light scattering detector (Wyatt Technology, Santa Barbara, CA) was used. For data acquisition and evaluation of the light-scattering experiments, Astra version 4.73 (Wyatt Technology, Santa Barbara, CA) was used. The light-scattering instrument was calibrated using pure toluene, assuming a Rayleigh ratio of \(9.78\times 10^{-6}\) cm\({}^{-1}\) at 690 nm. An injection volume of 118 \(\upmu\)L, a sample concentration of 1-2 g L\({}^{-1}\), a column temperature of 35 \({}^{\circ}\)C and a THF flow rate of 1 mL min\({}^{-1}\) have been applied. SEC analysis was performed on a high resolution column set from PSS (SDV 5 \(\upmu\)m 106 A, SDV 5 \(\upmu\)m 105 A, SDV 5 \(\upmu\)m 1000 A). Subsequent slow addition of monomer for the PS latex synthesis was carried out by using a precision piston pump (mikro Prominent). TEM experiments were carried out with a Zeiss EM 10 electron microscope operating at 80 kV. All shown images were recorded with a slow-scan charge-coupled device (CCD) camera obtained from TRS (Trondle) in bright field mode. Camera control was computer aided using the ImageSP software from TRS. Centrifugation was performed with an Avanti J-30I from Beckman Coulter for half an hour with a speed of 17,000 rpm. Dynamic light scattering (DLS) experiments were performed with a setup based on a He-Ne laser with a wavelength of \(\lambda\) = 632.8 nm and a goniometer allowing one to measure at scattering angles 20 from 30\({}^{\circ}\) to 160\({}^{\circ}\). Polarization of the primary beam was defined by a Glan-Thomson prism. The scattered beam polarization was again analyzed for its polarization, and all experiments were performed in vertical-vertical geometry. Scattered intensity was detected with an optical fiber coupled to two phototubes. In this way, background could be minimized using the cross-correlated signal from both tubes. The correlation function of intensity was calculated with an ALV 5000 autocorrelator. The sample was filled in a cylindrical cuvette (Hellma) and immersed in a temperature controlled index matching bath. DLS measurements were carried out at 25 \({}^{\circ}\)C in THF. The concentrations of the nanoparticle dispersions were approximately 0.01 w% after ultrasonic treatment (3 h for the polymer-grafted particles and 6 h for bare PS particles). After that sonication time, the experimentally obtained value of the hydrodynamic radius, R\({}_{\mathrm{h}}\), was constant. The scattering intensity was measured in a range of scattering angles, \(\theta\), from 50\({}^{\circ}\) to 130\({}^{\circ}\). The autocorrelation function of intensity, g\({}_{2}\)(t, \(q\)), was thus obtained. SAXS measurements were carried using a custom made system. The scattered intensity was measured as a function of scattering vector \(q=4\pi\lambda\mathrm{sin}\theta\), where \(\lambda\) is the X-ray wavelength and 2\(\theta\) the scattering angle. The experimental setup used monochromatized Cu K\({}_{a}\) radiation with \(\lambda\) = 1.54 A, a pinhole collimation and a two-dimensional position sensitive detector by Molecular Metrology. The accessed q-range is from 0.008 A\({}^{-1}\) to 0.25 A\({}^{-1}\). The two-dimensional scattering image from the detector was calibrated using Ag-behenate and radially averaged to calculate the intensity I(\(q\)).