Controlled chemical stabilization of self-assembled PS-P4VP nanostructures

Supramolecular self-assemblies in selective solvents give rise to many patterning possibilities. The diblock copolymer polystyrene-b-poly(4-vinylpyridine) (PS-P4VP) is one such polymer that self-assembles into neat nanostructures in toluene. These nanostructures once formed are highly susceptible to solvent influence. Unfortunately, for use as nanotemplates and in the synthesis of nanoparticles, the susceptibility of the films to solvents can be a problem. In this study, we present a method to stabilize the structures through chemical means in solution. We used 1,4-dibromobutane in solution to chemically crosslink the pyridine residues of each of PS-P4VP to yield a series of stable spherical aggregates. In this way, the cross-linking ratio can be precisely controlled. The solution properties were studied using dynamic light scattering and small angle X-ray scattering and the morphology of the resulting micellar film was studied using transmission electron microscopy (TEM). The size of the micelles formed was found to be dependent on the amount of cross-linking and the shape of the PS-P4VP micelles remains stable when exposed to a selective solvent for PS.