Polyisobutenylsuccinimide Derivatives: Synthesis and Their Application in the Dispersing of TiO2 Nanoparticles

A series of polyisobutenylsuccinimide derivatives, in which polyisobutenylene block with a definite chain length was linked with four different ethylenediamine end groups (diaminoethane, diethylenetriamine, triethylenetetraamine, and tetraethylenepentaamine), were synthesized and used to disperse TiO2 nanoparticles in nonpolar solvent. The influences of the sizes of hydrophilic/hydrophobic groups on the dispersibility of TiO2 nanoparticles were investigated, and it was found that: when the molecular weight of polyisobutenylene block was fixed at 2000, Zeta potentials of TiO2 particles increased while their particle sizes decreased with the increasing of the length of ethylenediamine chain in the dispersants, implying that the interactions between the dispersant and TiO2 nanoparticles became stronger. It was also disclosed that when the polyamine end group came to be tetraethylenepentaamine, polyisobutenylsuccinimide with a 2000 molecualr weight of polyisobutenylene block showed the best dispersing ability while compared to those with 1000 and 3000 molecular weights of polyisobutenylene segments. Thus, the most appropriate HLB (hydrophile-lipophile balance) value of the dispersant was estimated as around 2.5. The obtained TiO2 nanoparticles treated with such a dispersant demonstrated good electrophoretic displays.