Morphological Characterization of High Molecular Weight Poly(styrene-b-isoprene) or PS-b-PI and Its Hydrogenated, Sulfonated Derivatives: An AFM Study.

The surface morphology of high molecular weight poly(styrene-b-isoprene) block copolymer was analyzed after chemical modification. Poly(styrene-b-isoprene) was converted into poly(styrene-b-(ethylene-alt-propylene)) by hydrogenation and into poly(styrene-b-sulfonated isoprene) by mild sulfonation of the PI block. Obtained morphologies were examined by atomic force microscopy, analyzing the effect of sample preparation parameters such as solvent (tetrahydrofuran, toluene, and cyclohexane), casting technique (spin casting and drop casting), and annealing temperature [room temperature, 80, 100, and 120 °C]. Significant morphological and topographical changes were found depending on the different parameters. Each modification step introduces new variables that can affect the final structure and properties of the copolymer. Finding the balance between solvent choice, casting technique, and annealing conditions was a difficult task and required extensive experimentation and understanding of the principles of block copolymer self-assembly.