Adjusting Interface Action and Spacing for Control of Particle Potential

As the core issue of physical chemistry, how to acquire, control, even adjust surface charging of colloidal particle is far from being completely understood. So poly(lauryl methacrylate) (PLMA) is first introduced with different chain lengths onto crude anatase titanium dioxide (TiO₂) nanoparticles (150-200 nm) through two-step surface modification. Along with rising basic nonionic polyisobutylene succinimide (PIBS) concentration, those modified TiO₂ nanoparticles (TiO₂-NH-PLMA) with the low grafting amount (0.33-4.86 wt.%) and the short chain of the grafted PLMA fragments (layer thickness: 3.0-6.9 nm) underwent charge reversal from being positively to negatively charged in nonpolar isododecane solution. And the more modified ones (PLMA grafting amount: 11.10%; layer thickness: 9.5 nm) remained original electropositivity under same conditions. Based on molecular dynamics simulation, once the repeating unit number exceeds 12, these long grafted PLMA chains will bring about strong steric hindrance to increase interface spacing and weaken interface action against PIBS absorption. This may propose a unique strategy for adjusting or stabilizing surface potential of colloid particles by grafted polymer chains. It is anticipated to provide a facile, precise, and promising control to electronic ink for electrophoretic display.