Facile and controllable synthesis of hybrid silica nanoparticles densely grafted with poly(ethylene glycol)

Abstract

Abstract We report that a mixture of good and poor solvents greatly enhances the grafting density of nanosized silica grafted with poly(ethylene glycol) ( PEG ) by the ‘grafting to’ method. Methoxypolyethylene glycol ( MPEG ) (molecular weight 750, 2000 and 4000 g mol −1 ) was modified in a controlled manner to prepare epoxide terminated PEG ( MPEG‐EO ). Silica nanoparticles were modified with N ‐(2‐aminoethy)‐3‐aminopropylmethyldimethoxysilane through the silanization coupling reaction to obtain a well‐defined siloxane structure. MPEG‐EO was coupled to the modified silica by the reaction of their terminal groups in a mixed solvent ( n ‐decane/toluene). The grafting density of MPEG‐EO was found to be controlled by the concentration of MPEG‐EO and the ratio of n ‐decane to toluene in the grafting system. Based on TGA , the maximum grafting density was found to be about 2.8, 1.47 and 0.76 chains nm −2 for molecular weights of 750, 2000 and 4000, respectively, which is extremely high compared to previous reports. This high grafting density can be explained by the decreased chain dimension of PEG in the presence of the poor solvent. The method can be applied to other nanoparticles and polymers which can greatly enhance the application of SiO 2 nanocomposites. © 2017 Society of Chemical Industry