Hierarchical Self-Assembly of Symmetric Supramolecular Double-Comb Diblock Copolymers: A Comb Density Study

A double-comb diblock copolymer was constructed experimentally using a double supramolecular approach. Addition of 3-nonadecylphenol (3-NDP) amphiphiles to a symmetric, double hydrogen bond accepting poly(4-vinylpyridine)-block-poly(N-acryloylpiperidine) (P4VP-b-PAPI) diblock copolymer resulted in microphase separation on both the block copolymer and polymeramphiphile level. Variation of the comb density x in these [P4VP-b-PAPI](3-NDP)_x supramolecular complexes gave rise to several unique hierarchical nanostructures. For high comb densities (x = 0.8 - 1.2) double perpendicular lamellae-in-lamellae were observed, while lowering the density to x = 0.5 resulted in a double parallel lamellar morphology as demonstrated by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Further decreasing the concentration of 3-NDP (x = 0.3) caused the complex to self-assemble into cylinders-in-lamellae, while for x = 0.1 3-NDP only serves as a plasticizing agent. The phase transitions identified as a function of x are all in excellent agreement with our previously performed theoretical analysis.