## 3 Results and Discussions
### Synthesis of Polymer-Grafted Nanoparticles
In the spectrum of SiO\({}_{2}\)-\(g\)-PtBA, the absorption peak at 1730 cm\({}^{-1}\) belongs to the stretching vibration of the -O-C=O group (Figure 2d), and the absorption peak at 3410 cm\({}^{-1}\) in the spectrum of SiO\({}_{2}\)-\(g\)-PAA belongs to the -OH group formed after the hydrolysis of tBA (Figure 2e). In the spectrum of SiO\({}_{2}\)-\(g\)-P(OEGMA\({}_{50}\)-\(stat\)-tBA\({}_{50}\)), the absorption peak at 1730 cm\({}^{-1}\) belongs to the stretching vibration of the -O-C=O group (Figure 2f), and the absorption peak at 3410 cm\({}^{-1}\) in the spectrum of SiO\({}_{2}\)-\(g\)-P(OEGMA\({}_{50}\)-\(stat\)-AA\({}_{50}\)) belongs to the -OH group formed after the hydrolysis of tBA (Figure 2g). The results of the FT-IR spectrum indicate that the polymers were successfully grafted onto silica particles. In addition, the chemical compositions of the prepared free polymers, including POEGMA, PtBA, P(OEGMA\({}_{30}\)-\(stat\)-tBA\({}_{70}\)), P(OEGMA\({}_{50}\)-\(stat\)-tBA\({}_{50}\)), and P(OEGMA\({}_{70}\)-\(stat\)-tBA\({}_{30}\)) were characterized by NMR. The \({}^{1}\)H NMR spectrum of POEGMA (Figure 3a) shows all the characteristic peaks of polymer, the signals at 1.89 ppm and 1.65 ppm are attributed to -CH\({}_{2}\)- and -CH\({}_{3}\) of the main polymer chain, respectively. The signals between 3.41-4.25 ppm and at 3.31 ppm are attributed to -CH\({}_{2}\)- and -CH\({}_{3}\) of OEGMA, respectively. For PtBA (Figure 3b), the signals at 2.25 ppm and 1.75 ppm are attributed to -CH\({}_{2}\)- and -CH\({}_{3}\) of the main polymer chain, respectively. The signal at 1.41 ppm is attributed to -CH\({}_{3}\) in the side chain. The \({}^{1}\)H NMR spectrum of P(OEGMA\({}_{30}\)-\(stat\)-tBA\({}_{70}\)), P(OEGMA\({}_{50}\)-\(stat\)-tBA\({}_{50}\)) and P(OEGMA\({}_{70}\)-\(stat\)-tBA\({}_{30}\)) are shown in Figure 3c. The signals at 1.4 ppm are attributedto -CH\({}_{3}\) of tBA, the area of the peaks increases with tBA content in the polymers. The signals between 3.49-4.25 ppm and at 3.41 ppm are attributed to -CH\({}_{2}\)- protons and -CH\({}_{3}\) of OEGMA. These results indicate that the polymerization of the monomers was successful. The TGA thermograms obtained from the bare silica, amino-modified silica, initiator-functionalized silica, and polymer-grafted nanoparticles are shown in Figure 4. A weight loss of 13.1%, 16.1%, and 19.1% was observed from the TGA curve of SiO\({}_{2}\), SiO\({}_{2}\)-NH\({}_{2}\), and SiO\({}_{2}\)-Br, respectively. The weight loss of bare silica nanoparticles was likely due to the continued condensation reaction and associated water loss [33]. The TGA result shows that 3.0 wt% difference in the weight retentions of the amino-modified and initiator-modified silica nanoparticles. The grafting density of the initiators on the silica nanoparticles' surface was calculated to be 2.43 initiator/nm\({}^{2}\), if assuming the density of the silica nanoparticles is identical to that of the bulk silica (2.07 g/cm\({}^{3}\)) [34] and using the residual mass of the amino-modified silica nanoparticles as the reference. Moreover, a weight loss of 27.6%, 29.5%, 32.1%, 28.2%, and 39.5% were observed from the curve of SiO\({}_{2}\)-g-PtBA, SiO\({}_{2}\)-g-POEGMA, SiO\({}_{2}\)-g-P(OEGMA\({}_{30}\)-_stat_-tBA\({}_{70}\)), SiO\({}_{2}\)-g-P(OEGMA\({}_{50}\)-_stat_-tBA\({}_{50}\)), and SiO\({}_{2}\)-g-P(OEGMA\({}_{70}\)-_stat_-tBA\({}_{30}\)), respectively. The weight loss of the polymer-grafted nanoparticles is due to the grafted polymer decomposing into small molecules at sufficiently high temperatures. These results indicate that the polymers were successfully grafted onto the silica nanoparticle by SI-ATR. The molecular weight and molecular weight distribution of the free polymers, including POEGMA, PtBA, P(OEGMA\({}_{30}\)-_stat_-tBA\({}_{70}\)), P(OEGMA\({}_{50}\)-_stat_-tBA\({}_{50}\)), and P(OEGMA\({}_{70}\)-_stat_-tBA\({}_{30}\)), were determined by GPC.