Imidization of styrene–maleic anhydride copolymer for dispersing nano-SiO2 in water

Achieving functional styrene–maleic anhydride (SMA) copolymer dispersant is highly attractive but still remains a challenge. Conventional modified SMA dispersants have complex modification steps, poor performance, and limited applications. Thus, a series of styrene–maleimide (SMI) copolymers with different functionality as amphiphilic dispersants for dispersing nano-SiO 2 in an aqueous solution were synthesized using a simple preparation process. The changes in the maleic anhydride groups during imidization were tracked using FTIR spectroscopy, 1 H-NMR, and GPC. A rotational viscometer and an inverted bottle method were used to measure the viscosity and coagulation time of the nano-SiO 2 aqueous dispersion system, respectively, after adding the SMI dispersants. The particle size, size distribution, and dispersant adsorption amount of the dispersion were analyzed using laser particle size analysis; FTIR spectroscopy and SEM; and TGA, respectively. The results showed that the hydrogen bonds formed between the amino groups in the dispersant and the hydroxyl groups on the SiO 2 surface during stirring allowed the dispersant to be adsorbed onto the SiO 2 surface after being added to the nano-SiO 2 aqueous system. The addition of the SMI dispersant enhanced the steric hindrance and electrostatic repulsion between the nanoparticles, thus making it possible for the SiO 2 nanoparticles not to easily aggregate in water, improving their dispersity and stability. Additionally, the type and amount of SMI dispersant used significantly affected the SiO 2 nanoparticles' ability to disperse in water. This makes SiO 2 particles convenient to use and transport, not produce dust pollution, and easy to store. Graphical abstract