Non-spherical nanostructures derived from soft matter and with uniform size-that is, monodisperse materials-are of particular utility and interest, but are very rare outside the biological domain. We report the controlled formation of highly monodisperse cylindrical block copolymer micelles (length dispersity < or = 1.03; length range, approximately 200 nm to 2 microm) by the use of very small (approximately 20 nm) uniform crystallite seeds that serve as initiators for the crystallization-driven living self-assembly of added block-copolymer unimers with a crystallizable, core-forming metalloblock. This process is analogous to the use of small initiator molecules in classical living polymerization reactions. The length of the nanocylinders could be precisely controlled by variation of the unimer-to-crystallite seed ratio. Samples of the highly monodisperse nanocylinders of different lengths that are accessible using this approach have been shown to exhibit distinct liquid-crystalline alignment behaviour.

With the aim of accessing colloidally stable, fiberlike, π-conjugated nanostructures of controlled length, we have studied the solution self-assembly of two asymmetric crystalline-coil, regioregular poly(3-hexylthiophene)-b-poly(2-vinylpyridine) (P3HT-b-P2VP) diblock copolymers, P3HT23-b-P2VP115 (block ratio=1:5) and P3HT44-b-P2VP115 (block ratio=ca. 1:3). The self-assembly studies were performed under a variety of solvent conditions that were selective for the P2VP block. The block copolymers were prepared by using Cu-catalyzed azide-alkyne cycloaddition reactions of azide-terminated P2VP and alkyne end-functionalized P3HT homopolymers. When the block copolymers were self-assembled in a solution of a 50% (v/v) mixture of THF (a good solvent for both blocks) and an alcohol (a selective solvent for the P2VP block) by means of the slow evaporation of the common solvent; fiberlike micelles with a P3HT core and a P2VP corona were observed by transmission electron microscopy (TEM). The average lengths of the micelles were found to increase as the length of the hydrocarbon chain increased in the P2VP-selective alcoholic solvent (MeOH3 μm) fiberlike micelles were prepared by the dialysis of solutions of the block copolymers in THF against iPrOH. Furthermore the widths of the fibers were dependent on the degree of polymerization of the chain-extended P3HT blocks. The crystallinity and π-conjugated nature of the P3HT core in the fiberlike micelles was confirmed by a combination of UV/Vis spectroscopy, photoluminescence (PL) measurements, and wide-angle X-ray scattering (WAXS). Intense sonication (iPrOH, 1 h, 0 °C) of the fiberlike micelles formed by P3HT23-b-P2VP115 resulted in small (ca. 25 nm long) stublike fragments that were subsequently used as initiators in seeded growth experiments. Addition of P3HT23-b-P2VP115 unimers to the seeds allowed the preparation of fiberlike micelles with narrow length distributions (L(w)/L(n) < 1.11) and lengths from about 100-300 nm, that were dependent on the unimer-to-seed micelle ratio.

The redox properties of verdazyl radicals are presented using cyclic voltammetry techniques. These radicals can be reversibly reduced as well as oxidized. Electron-donating and -withdrawing substituents have significant effects on the oxidation and reduction potentials as well as the cell potential (E(cell) = | E(ox) degrees - E(red) degrees |) for these radicals; a correlation between the electron spin distribution and redox properties is developed.

The self-assembly of block copolymers in selective solvents represents a powerful approach to functional core-shell nanoparticles. Crystallization of the core can play a critical role in directing self-assembly toward desirable, nonspherical morphologies with low mean interfacial curvature. Moreover, epitaxial growth processes have been implicated in recent advances that permit access to monodisperse cylinders, cylindrical block comicelles with segmented cores and/or coronas, and complex hierarchical architectures. However, how the core-forming block crystallizes in an inherently curved nanoscopic environment has not been resolved. Herein we report the results of synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) studies of well-defined, monodisperse crystalline-coil polyisoprene-block-polyferrocenylsilane cylindrical micelles aligned in an electric field. WAXS studies of the aligned cylinders have provided key structural information on the nature of the PFS micelle core together with insight into the role of polymer crystallinity in the self-assembly of these and potentially related crystalline-coil block copolymers.

Water-soluble, high-molecular-weight polycobaltocenium polyelectrolytes have been prepared by ring-opening polymerization (ROP) techniques. Anionic polymerization of a strained 19-electron dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium chloride resulted in the formation of oligomers with up to nine repeat units. Thermal ROP of dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium nitrate resulted in the formation of high-molecular-weight polycobaltocenium nitrate, a redox-active cobalt-containing polyelectrolyte.

The straightforward synthesis of a series of 3-cyanoformazanate boron difluoride dyes is reported. Phenyl, 4-methoxyphenyl and 4-cyanophenyl N-substituted derivatives were isolated and characterized by single-crystal X-ray crystallography, cyclic voltammetry, and UV/Vis spectroscopy. The compounds were demonstrated to possess tunable, substituent-dependent absorption, emission, and electrochemical properties, which were rationalized through electronic structure calculations.

Formazans react with boron triacetate to produce boratatetrazines, which can be reduced to yield borataverdazyl radical anions--the first boron containing verdazyl radicals.

Metal-containing polymers are attracting growing attention as functional materials as a result of the useful physical and catalytic properties that arise from the presence of metal centers.[1] For example, metallopolymers with reversible redox properties are of interest for applications in electrocatalysis [2] and sensing, [3] as responsive surfaces [4] and capsules, [5] and as the active components of photonic crystal displays.[6] Block copolymers containing metal centers present additional features of considerable interest as a result of their ability to undergo self-assembly in the solid state or solution. Studies of such materials have led to applications as nanotemplates in lithography [7] and as precursors to patterned magnetic nanostructures [8] and nanocatalysts for carbon nanotube growth.[9] However, the synthesis of materials containing metalloblocks by living polymerization protocols presents substantial challenges as a result of undesirable side reactions of many metal centers with ionic and radical propagating sites. Herein, we describe our initial results on the synthesis and properties of unusual main-chain heterobimetallic diblock copolymers with different redox-active centers in each metalloblock.The ring-opening polymerization (ROP) of strained metallocenophanes 1 provides a well-studied route to functional metallopolymers 2. [10][11][12] In particular, the ROP of 18-electron sila[1]ferrocenophanes (1, M= Fe, E x R y = SiR 2 ) represents a useful route to polyferrocenylsilanes (PFSs, 2, M = Fe, E x R y = SiR 2 ) which exhibit many interesting characteristics.[13] Living anionic polymerization of sila[1]ferrocenophanes (1, M = Fe, E x R y = SiR 2 ) using organolithium initiators such as nBuLi proceeds by cleavage of the Si-Cp bond (Cp = cyclopentadienyl), and has been developed as a route to a variety of PFS block copolymers.[14] An alternative procedure, living photocontrolled ROP in the presence of cyclopentadienide anion initiators, [15] involves photoactivation and subsequent cleavage of the Fe-Cp bond. + homopolymer and also ring-opening oligomerizations of 3 appeared to proceed through Co-Cp bond cleavage. [19] The successful synthesis of PFS-b- [PCE] + block copolymers was accomplished by sequential photocontrolled ROP of 1 (M = Fe, E x R y = SiMe 2 ) and 3 followed by oxidation of the 19-electron cobaltocene centers (Scheme 1). [19][20][21][22] The living PFS blocks were synthesized by addition of sodium cyclopentadienide (NaCp) as initiator to a solution of 1 (M = Fe, E x R y = SiMe 2 ) in tetrahydrofuran (THF) under anhydrous conditions, followed by prolonged irradiation (5-24 h) of the solutions at 5 8C. The living PFS chains were then combined with 19-electron cobaltocenophane 3, and the solutions irradiated at 20 8C (to increase solubility) until the block copolymers precipitated from solution (15-24 h). The living polymer chains were quenched by, and the resulting product washed with degassed methanol, oxidized by air in the presence of ammonium triflate ([NH 4 ][OTf]), and dia...