Towards Monodomains of Self-Organized Comb-Shaped Polymeric Supramolecules

Abstract

AbstractWe have previously shown that hierarchical self-organization is achieved upon physically bonding amphiphilic molecules to diblock copolymers. Here we discuss the effect of imposed shear flow to achieve overall alignment of the locally self-organized structures. We will first present shear aligned polystyrene-block-poly(4-vinyl pyridine) diblock copolymers (PS-b-P4VP), where pentadecyl phenol (PDP) has been hydrogen bonded to the pyridines. Depending on the selected molecular weights, eg. hexagonal arrangement of PS cylinders in the lamellar matrix of P4VP(PDP) can be obtained with high overall order of both structures. This is a template to obtain discrete PS nanorods, which have P4VP corona once the PDP molecules have been cleaved off by a solvent treatment. Selecting a relatively high molecular weight PS block and a short P4VP block leads to mesoporous materials with emptied cylinders with P4VP brushes at the walls. The glassy state of the PS matrix prevents the pores from collapsing. The pyridine groups of PS-b-P4VP can be protonated using eg. toluene sulphonic acid and the resulting polymeric salt has been complexed using PDP. The weight fractions have been selected so that the polyelectrolyte/amphiphile complex self-organizes into cylindrical domains with hexagonal packing. Shear alignment leads to high overall order. SAXS in combination with structural models suggests that within the cylinders there are parallel self-organized layers. The conductivity is anisotropic. We will also discuss dielectric reflectors based on self-organized block polyelectrolytes consisting PS-b-P4VP where DBSA has been complexed to P4VP. In this case, plasticization due to the oligomeric side chains promotes a facile structure formation at long periodicities in comparison to concepts based on eg. blends of high molecular weight polymers and block copolymers. Finally, plasticized comb-shaped supramolecules based on rigid conjugated poly(p-pyridine) are discussed. Even gentle shearing leads to highly aligned lamellar structures, which show efficient polarized photoluminescence.