Shear alignment at two length scales:Comb-shaped supramolecules self-organized as cylinders-within-lamellar hierarchy

Large-amplitude oscillatory shear alignment of a hierarchically ordered system of comb-shaped supramolecules and the preparation of core-corona nanorods thereof are reported. The supramolecules consist of nearly symmetric polystyrene-b-poly(4-vinylpyridine) diblock copolymers with pentadecylphenol side chains hydrogen bonded to the poly(4-vinylpyridine) blocks. The polystyrene blocks, accounting for approximately 20% (w/w) of the supramolecules, are segregated in hexagonally ordered cylinders inside a matrix formed by the comb-shaped poly(4-vinylpyridine)-based blocks. The matrix further self-organizes in a layered structure below the order-disorder transition temperature of 70 degreesC. Thus, a cylinder-within-lamellar morphology is formed. Imposing shear leads to considerable alignment of both structures. The cylinders align along the shear flow with the (10) plane parallel with respect to the shear plane. The matrix layers align perpendicular to the cylinders, transverse to the flow. After elimination of pentadecylphenol by dialysis, crew-cut rods of 20-25 nm in diameter and 5-10 mum in length are obtained.