Synthesis of PS-b-PEG Grafted SiO2 Nanoparticles with Room Temperature Esterification Method

Polystyrene-poly(ethylene glycol) copolymer grafted SiO2 composite nanoparticles (SiO2-PS-PEG) were in this study synthesized via room temperature esterification method. The successful synthesis of the SiO2-PS-PEG was confirmed by Fourier transform infrared spectroscopy (FT-IR), proton magnetic resonance (H-1-NMR), gel permeation chromatography (GPC), and X-ray photoelectron spectroscopy (XPS). Results from the 1H-NMR analysis showed that the incorporated weight of PS and PEG in the grafted PS-PEG diblock copolymer accounted for 58.0 wt% and 42.0 wt%, respectively, which were very close to the theoretical amount of 56.3 wt% and 43.7 wt%, respectively. Results from the X-ray diffraction (XRD) showed that the grafted PS domain existed in the amorphous phase while the grafted PEG domain presented in the crystal phase with monoclinic structure. Additionally, results from the differential scanning calorimetry (DSC) showed that the glass transition temperature of the grafted PS increased about 21.4 degrees C as compared to that of the ungrafted PS. This was because of PS chains mobility hindering after the PS chains grafting onto the SiO2 nanoparticles. In addition, similar hindering of the PEG chains mobility after the PEG chains grafting onto the SiO2 nanoparticles resulted into less crystals or faulty crystals. Consequently, the grafted PEG melting point decreased ca. 10.8 degrees C, as compared to that of the free PEG.