Supramolecular routes to hierarchical structures: Comb-coil diblock copolymers organized with two length scales

We show that polymeric materials characterized by two length scales are obt ained if diblock copolymers are mixed with amphiphilic selective solvents, leading to self-organization which combines the "block copolymer length sca le" with a much shorter "nanoscale". In this work, the amphiphilic compound is 3-n-pentadecylphenol (PDP) which is hydrogen-bonded to the pyridine gro up of polystyrene-block-poly(4-vinylpyridine), i.e., PS-b-P4VP, The molecul ar architecture resembles comb-coil diblock. copolymers A-block-(B-graft-C) but is obtained using the supramolecular assembly route. The structures we re determined with. a combination of transmission electron microscopy and s mall-angle X-ray scattering. On the block copolymer scale (300 A range), th e PS blocks are microphase-separated from the P4VP(PDP)(x) blacks, where x denotes the ratio between the number of phenol and pyridine groups. For PS- b-P4VP block copolymers having a spherical morphology and P4VP as the minor ity component, the structure of PS-b-P4VP(PDP)(x) changes from spherical to hexagonal and further to lamellar as a function of the amount of PDP added . For all comb-call diblock copolymer morphologies, the P4VP(PDP)(x) domain s are further "nanophase-separated" into lamellar structures due to microph ase separation of the comb copolymer-like complex between P4VP and PDP, The morphology diagram is presented for stoichiometric conditions (x = 1), usi ng a range of different PS-b-P4VP block copolymers.