Adam Nunns

Large-Area Nanosquare Arrays from Shear-Aligned Block Copolymer Thin Films

While block copolymer lithography has been broadly applied as a bottom-up patterning technique, only a few nanopattern symmetries, such as hexagonally packed dots or parallel stripes, can be produced by spontaneous self-assembly of simple diblock copolymers; even a simple square packing has heretofore required more intricate macromolecular architectures or nanoscale substrate prepatterning. In this study, we demonstrate that square, rectangular, and rhombic arrays can be created via shear-alignment of distinct layers of cylinder-forming block copolymers, coupled with cross-linking of the layers using ultraviolet light. Furthermore, these block copolymer arrays can in turn be used as templates to fabricate dense, substrate-supported arrays of nanostructures comprising a wide variety of elements: deep (>50 nm) nanowells, nanoposts, and thin metal nanodots (3 nm thick, 35 nm pitch) are all demonstrated.

Ordered nanoscale Archimedean tilings of a templated 3-miktoarm star terpolymer.

The directed self-assembly of 3-miktoarm star terpolymer chains (polyisoprene-arm-polystyrene-arm-polyferrocenylethylmethylsilane (3 μ-ISF)) into 2D Archimedean tilings is described. A morphological change from (4.8(2)) to (6(3)) tiling is reported in the 3 μ-ISF thin film blended with PS homopolymer when a greater swelling of PI is achieved during the solvent annealing process. Highly oriented (4.8(2)) tilings were produced by templating the self-assembled three colored structures in blended thin films. The use of (4.8(2)) and (6(3)) tilings as nanolithographic masks to transfer square and triangular hole arrays into the substrate is also demonstrated.

Thin film knitting pattern morphology from a miktoarm star terpolymer.

Thin film knitting pattern from a miktoarm star terpolymer is demonstrated. Such structures have been predicted but not observed in bulk or thin film form. The knitting pattern exhibits well organized periodic structures consisting of undulating lamellae and alternating cylinders, with well-defined defects that result in sharp 90° bends and T junctions.

Synthesis and self-assembly of poly(ferrocenyldimethylsilane)-block-poly(2-alkyl-2-oxazoline) block copolymers

Herein, we demonstrate the synthesis of chain-end functionalized poly(ferrocenyldimethylsilane) (PFDMS) and poly(2-alkyl-2-oxazoline)s (POx) of different molar mass, and the subsequent macromolecular conjugation to organometallic PFDMS-b-POx block copolymers of different composition via copper-catalyzed azide–alkyne cycloaddition (CuAAC). We distinguish between amphiphilic crystalline-coil PFDMS-b-PEtOx (poly(2-ethyl-2-oxazoline)) and potentially double crystalline PFDMS-b-PiPrOx (poly(2-iso-propyl-2-oxazoline)) materials. After characterization of the obtained block copolymers via SEC, NMR, FT-IR and X-ray scattering, the solution behavior in acetone as a non-solvent for PFDMS was investigated. We found various aggregate morphologies with a PFDMS core and a POx corona (sheets, vesicles, rods), depending on the weight fraction of the organometallic PFDMS segment.

Square and Rectangular Symmetry Tiles from Bulk and Thin Film 3‐Miktoarm Star Terpolymers

The directed self assembly of a 3-miktoarm star terpolymer (polyisoprene-arm-polystyrene-arm-polyferrocenylethylmethylsilane (3μ-ISF)) into a (4.8²) square symmetry Archimedean tiling pattern is described. Bulk samples of 3μ-ISF generate equilibrium columnar (4.8²) tile patterns (symmetry p 4 mm) on annealing, which is preceded by a metastable c 2 mm centered rectangular structure. In contrast, in thin films of 3μ-ISF blended with PS homopolymer, the c 2 mm phase is stable with columns oriented out of plane when the film thickness is below 50 nm. However, the 3μ-ISF/homopolymer blend rapidly forms a p 4 mm symmetry when the film thickness is ∼80 nm, with grain sizes of several μm and excellent order. Defects in the p 4 mm structure are described.

Cyclopropenylidene carbene ligands in palladium catalysed coupling reactions: carbene ligand rotation and application to the Stille reaction

Reaction of [Pd(PPh(3))(4)] with 1,1-dichloro-2,3-diarylcyclopropenes gives complexes of the type cis-[PdCl(2)(PPh(3))(C(3)(Ar)(2))] (Ar = Ph 5, Mes 6). Reaction of [Pd(dba)(2)] with 1,1-dichloro-2,3-diarylcyclopropenes in benzene gave the corresponding binuclear palladium complexes trans-[PdCl(2)(C(3)(Ar)(2))](2) (Ar = Ph 7, p-(OMe)C(6)H(4)8, p-(F)C(6)H(4)9). Alternatively, when the reactions were performed in acetonitrile, the complexes trans-[PdCl(2)(NCMe)(C(3)(Ar)(2))] (Ar = Ph 10, p-(OMe)C(6)H(4)11 and p-(F)C(6)H(4)) 12) were isolated. Addition of phosphine ligands to the binuclear palladium complex 7 or acetonitrile adducts 11 and 12 gave complexes of the type cis-[PdCl(2)(PR(3))(C(3)(Ar)(2))] (Ar = Ph, R = Cy 13, Ar = p-(OMe)C(6)H(4), R = Ph 14, Ar = p-(F)C(6)H(4), R = Ph 15). Crystal structures of complexes 6·3.25CHCl(3), 10, 11·H(2)O and 12-15 are reported. DFT calculations of complexes 10-12 indicate the barrier to rotation about the carbene-palladium bond is very low, suggesting limited double bond character in these species. Complexes 5-9 were tested for catalytic activity in C-C coupling (Mizoroki-Heck, Suzuki-Miyaura and, for the first time, Stille reactions) and C-N coupling (Buchwald-Hartwig amination) showing excellent conversion with moderate to high selectivity.

Hierarchical Self-Assembly of Double-Crystalline Poly(ferrocenyldimethylsilane)-block-poly(2-iso-propyl-2-oxazoline) (PFDMS-b-PiPrOx) Block Copolymers

The step-wise solution self-assembly of double crystalline organometallic poly(ferrocenyldimethylsilane)-block-poly(2-iso-propyl-2-oxazoline) (PFDMS-b-PiPrOx) diblock copolymers is demonstrated. Two block copolymers are obtained by copper-catalyzed azide-alkyne cycloaddition (CuAAC), featuring PFDMS/PiPrOx weight fractions of 46/54 (PFDMS30-b-PiPrOx75) and 30/70 (PFDMS30-b-PiPrOx155). Nonsolvent induced crystallization of PFDMS in acetone leads in both cases to cylindrical micelles with a PFDMS core. Afterward, the structures are transferred into water for sequential temperature-induced crystallization of the PiPrOx corona, leading to hierarchical double crystalline superstructures, which are investigated using scanning electron microscopy, wide angle X-ray scattering, and differential scanning calorimetry.