Synthesis of hollow silica nanoparticles using poly (acrylic acid) (PAA)-amine aggregates as nano-sized template was proposed. The PAA-amine mixtures dissolve in water, but not in ethanol, therefore the mixtures can be a template for hollow particle in ethanol and can be removed from the core-shell particle by addition of water. In order to investigate effect of amines on hollow particle formation, four kinds of amines; ethylenediamine (EDA), N,. N,. N',. N'-tetramethylethylenediamine (TED), 3,3'-diaminodipropylamine (DDA), triethylenetetramine (TTA), which interact with carboxylic acid of PAA were chosen. The PAA-each amine nanoparticles were formed with around 200. nm by dropping of PAA/amine mixtures in ethanol under the optimum conditions. Using the PAA-DDA template, hollow silica nanoparticles with spherical form were successfully prepared for the shortest reaction time in four hours. The primary amines and secondary amine of DDA work as not only cross-linker for PAA, but also sol-gel reacting catalyst. It can be clear from that the EDA with two primary amines also worked as sol-gel catalyst while the TED with two tertiary amines didn't. On the other hands, TTA with two primary and secondary amines also provided hollow silica nanoparticles, however, the silica shell of particles were mostly collapsed. It could be thought that the four amines of TTA promote sol-gel reaction, at the same time, high water content in the template induces molecular motion.
Takai-Yamashita, C., Imabeppu, H., & Fuji, M. (2015). Synthesis of hollow silica nanoparticles using poly (acrylic acid)-3,3’-diaminodipropylamine template. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 483, 81–86. https://doi.org/10.1016/j.colsurfa.2015.07.022