395 research outputs found
Well-defined and stable nanomicelles self-assembled from brush cyclic and tadpole copolymer amphiphiles: a versatile smart carrier platform
No full textThis study reports the first well-defined and stable nanomicelles (20 - 30 nm in diameter) self-assembled from amphiphilic brush (comb-like) cyclic and tadpole-shaped copolymers composed of hydrophobic n-decyl and hydrophilic 2-(2-methoxyethoxy)ethoxy) ethyl bristle blocks based on a poly(glycidyl ether) backbone. The micelle formation behaviour and structural details were investigated by synchrotron X-ray scattering analysis in a rigorous and complementary manner. The amphiphilic brush cyclic topology facilitates more compact and stable aggregation behaviour in the micelle core and a more densely packed corona, which prevents intermicellar aggregation. The presence of a hydrophobic component with brush cyclic topology inside the core is identified as the primary micelle stabilizing factor, enabling stable core aggregation and sharper core-corona interface formation. The presence of a hydrophilic brush cyclic component in the corona is determined as the secondary micelle stabilizing factor, helping nullify the corona penetration by polymer chains from other micelles and ultimately prevent the intermicellar aggregation-mediated collapse of the micellar structure. Overall, the brush cyclic topology was confirmed to be beneficial for forming highly stable nanomicelles with an extremely narrow (pseudo-monodisperse) size distribution compared with conventional linear topology and tadpole topologies. All the results of this study provide a unique opportunity for designing advanced functional high-performance amphiphilic materials for nanomicelles that are unattainable by other conventional methods and broadening their applications in various fields, including drug delivery, biomedical imaging, foods, cosmetics, smart coatings, photonics and molecular electronics. c. The Author(s) 201711sci
High-Performance n-Type Electrical Memory and Morphology-Induced Memory-Mode Tuning of a Well-Defined Brush Polymer Bearing Perylene Diimide Moieties
No full textPoly(N-(1-hexylheptyl)-N'-(12-oxydodecyl)perylene-3,4,9,10-tetracarboxyldi-imide acrylate) (PAcPDI), a perylene diimide (PDI) containing brush polymer, is synthesized, revealing good solubility in organic solvents, excellent thermal stability up to around 340 degrees C, and two melting transitions over 130-220 degrees C. The self-assembly and n-type memory characteristics of PAcPDI in nanoscale thin films are quantitatively investigated. As-cast films of PAcPDI are completely amorphous and the PDI units nevertheless formed p-p stacks favorably. However, the PAcPDI molecules can self-assemble via thermal annealing, developing a well-ordered horizontal lamellar structure with monomorphic or polymorphic monoclinic PDI crystals. The formation of monomorphic or polymorphic monoclinic crystals is attributed to various p-p stack modes of the PDI units, and is shown to be dependent on the film thickness. The differences in the thin film morphologies are directly reflected into the electrical memory behavior. The thermally annealed films demonstrate high-performance n-type unipolar volatile memory behavior within the thickness range of 12-31 nm. The as-cast films show n-type unipolar nonvolatile or volatile memory behavior in the range of 12-53 nm. The memory mode of PAcPDI films can be tuned by changing either the morphology or the film thickness.11117sciescopu
Hierarchical Self-Assembly and Digital Memory Characteristics of Crystalline-Amorphous Brush Diblock Copolymers Bearing Electroactive Moieties
No full textTwo series of crystalline-amorphous brush diblock copolymers bearing electroactive moieties were newly synthesized by sequential anionic ring-opening copolymerizations of glycidyl derivatives and subsequent selective postfunctionalizations; their homopolymers and analogues were additionally synthesized. Self-assembly structural details and electrical memory behaviors of these polymers in nanoscale thin films were investigated. The diblock copolymers revealed complex hierarchical self-assembly structures depending on the compositions. The self-assembly structure and orientation of the crystalline block chains were severely affected by the geometrical confinement (i.e., size and shape) stemming from microphase separation. Such film morphologies were found to significantly influence the electrical properties; they exhibited electrical properties from p-type permanent memory behavior to dielectric-like behavior. The memory behaviors were governed by the trap-limited space charge limited conduction mechanism combined with ohmic conduction and the hopping paths composed of the electroactive moieties distributed locally. © 2016 American Chemical Society19101sciescopu
Investigation on the Mechanism behind Electrical Switching Behavior in Carbazole-Containing Polyimide Thin Films
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High Performance n-Type Digital Memory Devices Fabricated with Novel Fullerene Polymers
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Biocompatible Characteristics and Nanostructure of Glycopolymers: Synthesis, Bacterial Adhesion, Cell Adhesion and Structure
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Examining Cretaceous Strata of the Taylor Creek Group in British Columbia : Potential Connection of the Methow and Tyqughton Basins.
No full textColor poster with text and charts describing research conducted by Michelle Forgette, advised by J. Brian Mahoney.Cretaceous strata around the Chilcotin Plateau of
south-central British Columbia are traditionally described as occupying several distinct basins, including the Nechako, Methow and Tyaughton basins. The original geometric relationships between these basins are difficult to reconstruct
due to Eocene and Neogene volcanic cover and the presence of a Tertiary dextral transpressive fault system along the southern margin of the Plateau. Detailed sedimentologic and
stratigraphic analysis are being integrated with ongoing thin section petrography, shale geochemistry (REE and isotopes), palynology, macro- and microfossil studies, and detrital zircon analyses in both these formations to test this proposed stratigraphic correlation.University of Wisconsin--Eau Claire Office of Research and Sponsored Programs
Synthesis of Polypeptide by Nickel Complex Initiator and Their Alpha-Helical Self-assembly Behaviors
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A Comparative Study of Dynamic Light and X-ray Scatterings on Micelles of Topological Polymer Amphiphiles
No full textMicelles were prepared in organic solvents by using three topological polymer amphiphiles: (i) cyclic poly(n-decyl glycidyl ether-block-2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether) (c-PDGE-b-PTEGGE) and (ii) its linear analogue (l-PDGE-b-PTEGGE); (iii) linear poly(6-phosphorylcholinehexylthiopropyl glycidyl ether-block-n-dodecanoyl glycidyl ether) (l-PPCGE-b-PDDGE). For the individual micelle solutions, the size and distribution were determined by dynamic light scattering (DLS) and synchrotron X-ray scattering analyses. The synchrotron X-ray scattering analysis further found that c-PDGE-b-PTEGGE forms oblate ellipsoidal micelle in an ethanol/water mixture, l-PDGE-b-PTEGGE makes prolate ellipsoidal micelle in an ethanol/water mixture, and l-PPCGE-b-PDDGE forms cylindrical micelle in chloroform. This comparative study found that there are large differences in the size and distribution results extracted by DLS and X-ray scattering analyses. All possible factors to cause such large differences are discussed. Moreover, a better use of the DLS instrument with keeping its merits is proposed.11Ysciescopu
Thin Films of Miktoarm Star Polymers: Poly(n-hexyl isocyanate)(12k)-Poly(e-caprolactone)1~3(5K)
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