Atomic force microscopy imaging of novel macromolecular species,nanosponges, and their clusters

Atactic polystyrene of M = 330,000 Da and M_w/M_n = 1.04 was subjected to a complete chloromethylation. By heating the chloromethyl polystyrene with SnCl₄ in a very dilute solution in ethylene dichloride, the polymeric coils were converted into intramolecularly hypercrosslinked macromolecules, called “nanosponges.” These species have a molecular weight of about 370,000 Da and a diameter of about 17 nm. When in solution, the nanosponges display a tendency to reversibly self‐assemble into regular clusters. Preparative size‐exclusion chromatography isolates a fraction consisting predominantly of spherical clusters that are composed of 13 subunits and acquire a molecular weight of approximately 5.0 × 10⁶ Da and a diameter of 45 nm. Scanning atomic force microscopy (AFM) provides images of individual nanosponges, N = 13 clusters, as well as higher spherical clusters. The regular spherical species most probably belong to the cluster series N = 1 + ∑(10n² + 2), where n is the number of shells around the central nanosponge. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1451–1455, 1999