ABSTRACT
Apart from the aqueous solubility mentioned earlier, the other signi cant difference between ND and ND-PG is susceptibility to aggregation. As revealed by dynamic light scattering, ND30 displayed a very broad size distribution in water with a mean hydrodynamic diameter of 75.3 nm, indicating that large aggregates were included in the dispersion (Figure 28.2a). In the case of ND30-PG, the size distribution was much narrower, and its mean hydrodynamic diameter was as small as 46.9 nm (Figure 28.2b). Scanning transmission electron microscopy (STEM) images showed that ND30 particles were prone to aggregate, while ND30-PG particles were individually dispersed (Figure 28.2c and d). These results suggest that the grafted PG layer ef ciently protects ND-PG particles from aggregation by steric shielding.
