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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.

A small/wide-angle X-ray scattering and grazing incidence diffraction study of comb-shaped supramolecules of conjugated poly(2,5-pyridinediyl), acid dopant and hydrogen bonded amphiphilic side chains is reported. In solution, polymers are dissolved rodlike particles. When the side-chains are introduced, polymers self-assemble in hierarchic liquid crystals (LC). Diffraction patterns of aligned LC show h00, 020, and 004 reflections, and additional small-angle reflections along the polymer axis. A triangular correlation function indicating a very large correlation length is seen along the smectic axis. An aligned solid structure can be formed by cleaving side chains from the aligned LC.

Macroscopic orientation of self-organized supramolecular polymeric materials has been demonstrated by oscillatory shear flow using in-situ small-angle X-ray scattering (SAXS). In the case when a homopolymer poly(4-vinylpyridine) and pentadecylphenol molecules are stoichiometrically complexed to form comb copolymer-like supermolecules, the self-organized lamellar local structures align parallel when sheared below the order-disorder transition temperature at 56 °C using 0.5 Hz frequency and 100% strain amplitude. Therefore, the hydrogen bonds between the phenolic and pyridine groups are strong enough to withstand the applied flow. In the case of a diblock copolymer of polystyrene and poly(4-vinylpyridine) stoichiometrically complexed with pentadecylphenol molecules to form the supermolecules, the self-organization yields lamellar-within-lamellar local structure near room temperature. The larger lamellar diblock copolymer structure showed a parallel orientation relative to the shearing plates upon shearing at 125 °C (i.e., above the order-disorder transition of the short length scale comb copolymer-like structure) with initially 0.5 Hz and finally 1 Hz, both at 50% strain amplitude. On cooling, the short length scale lamellar structure, consisting of poly(4-vinylpyridine) block and pentadecylphenol, is formed inside the layers of the comb copolymer-like material in perpendicular orientation.

We show that in a hydrogen bonded LC side chain diblock copolymer with lamellar morphology on the block copolymer level, two distinct packing mechanisms of the side chain blocks are possible depending on the amount of hydrogen bonded side chains. We mixed a hydrogen bonding mesogen, cholesteryl hemisuccinate (CholHS), with poly(1,2-butadiene)-block-poly(2-vinylpyridine) (PBd-P2VP) and poly(styrene)-block-poly(4-vinylpyridine) (PS-P4VP), in which the poly(vinylpyridine) act as host blocks, and we varied the CholHS to pyridine repeat unit ratio (x). With all x, a lamellar morphology on the block copolymer level was achieved. However, at low binding of CholHS to the host block, the CholHS side chains microphase separated into a single layer inside the poly(pyridine) lamellae resulting in a novel microphase separated structure. This includes, for example, the PS-P4VP sample with x = 0.25 and all the PBd-P2VP based samples since hydrogen bonding of CholHS to P2VP was sterically limited as revealed by infrared spectroscopy. No such limits were present in the rest of the PS-P4VP samples which showed a gradual shift from the single CholHS lamella morphology to exclusively liquid crystalline smectic layers oriented perpendicular to the block domain interfaces. © 2012 American Chemical Society.

A tooth rheometer, designed to investigate in-situ the influence of large-amplitude oscillatory shear on the macroscopic orientation of complex fluids, is used to study the alignment of two supramolecular systems composed of a polyisoprene-block-poly(2-vinylpyi-idine) block copolymer with octyl gallate (OG) hydrogen bonded to the vinylpyridine block. The molecular ratio x between OG and pyridine groups in these two PI-b-P2VP(OG)(x) systems is 0.50 and 0.75, respectively. In both cases, a hexagonally ordered cylindrical self-assembly was revealed by small-angle X-ray scattering in a broad temperature range. The spacing of the hexagonal structure decreases significantly on heating and reversibly increases on cooling. In in-situ SAXS experiments, performed with the tooth rheometer, a gradual macroscopic alignment of the nanoscale structure is observed on heating for both supramolecular systems. The most striking feature is a shear-induced transition from one hexagonal structure to another, more aligned, hexagonal structure observed for PI-b-P2VP(OG)0.75 in the temperature range 120-140degreesC. The transition is accompanied by an abrupt reduction of the domain spacing and additionally by a decrease of the phase angle measured by the rheometer. In the PI-b-P2V-P(OG)(0.5) system a comparable reduction in the spacing is observed at 90-95degreesC. In this case, it coincides with the most intensive macroscopic alignment of the sample, proceeding in a continuous rather than discontinuous fashion. This behavior is discussed in terms of the breaking of the hydrogen bonds between OG and P2VP being facilitated by shear.

A facile concept to prepare nano-objects based on self-organizing polymeric supramolecules (also called supramolecular block copolymers) is demonstrated using one particular shape, i.e., nanorods or nanofibers. Cylindrical aggregates consisting of a polystyrene (PS) core and a thin corona of poly(4-vinylpyridine) (P4VP) chains are prepared from P4VP(pentadecylphenol)-block-PS comb-coil supramolecules. Diblock copolymers P4VP-block-PS are stoichiometrically (with respect to the number of pyridine groups) hydrogen-bonded with pentadecylphenol (PDP) amphiphiles to yield P4VP(PDP)-block-PS comb-coil supramolecules. By the selection of appropriate relative block lengths for P4VP(PDP) and PS, a micro-phase-separated cylindrical morphology of PS cylinders inside a P4VP(PDP) matrix is obtained. Subsequent removal of the amphiphiles, accounting for ca. 75% of the matrix material, results in cylinders with a core of PS and a corona of easily adjustable thickness of P4VP. The advantages of the present concept compared to the existing procedures are discussed.

It was demonstrated that polymeric supramolecular nanostructures with several length scales allow straightforward tailoring of hierarchical order-disorder and order-order transitions and the concurrent switching of functional properties. Poly(4-vinyl pyridine) (P4VP) was stoichiometrically protonated with methane sulfonic acid (MSA) to form P4VP(MSA) 1.0 , which was then hydrogen-bonded to pentadecylphenol. Microphase separation, re-entrant closed-loop macrophase separation, and high-temperature macrophase separation were observed. When MSA and pentadecylphenol were complexed to the P4VP block of a microphase-separated diblock copolymer poly[styrene- block -(4-vinyl pyridine)], self-organized structures-in-structures were obtained whose hierarchical phase transitions can be controlled systematically. This microstructural control on two different length scales (in the present case, at 48 and 350 angstroms) was then used to introduce temperature-dependent transitions in electrical conductivity.

Application to rod-likepolymers (such as p-conjugated electroactive polymers)could lead to possible new applications, but is not straight-forward because such polymers tend to be infusible andpoorly soluble. For polymers containing rod-like moieties,self-organization has been achieved based on di-block co-polymers with flexible blocks