Self-assembly of multiblock copolymers with two length scales

The morphology of self-assembled structures of AB diblock copolymers are well studied. Structures like cylinders, lamellae or more complex gyroid structures will be formed depending on the A/B volume fraction ratios. In addition to these diblocks more complex systems such as ABA triblock copolymers, ABC triblock copolymers and (AB)_n multiblock copolymers have been studied extensively as well.

The focus in our research is on A-(BA)_n-B multiblock copolymers composed of multiple short middle diblock units (n) and two long end blocks. Multiblock copolymers of polystyrene and poly(tert-butoxy styrene) were synthesized through sequential anionic polymerization giving hexa, octa and even hexadeca multiblock copolymers with a low overall polydispersity. The self-assembly of these multiblock copolymers was investigated using Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM). A unique two-length-scale lamellar morphology with multiple periodicities was observed for the octablock copolymer.