Helsinki University of Technology

About: Helsinki University of Technology is a based out in . It is known for research contribution in the topics: Thin film & Vortex. The organization has 8962 authors who have published 20136 publications receiving 723787 citations. The organization is also known as: TKK & Teknillinen korkeakoulu.

Self-Assembled Structures in Diblock Copolymers with Hydrogen-Bonded Amphiphilic Plasticizing Compounds

Abstract: Hydrogen-bonding amphiphilic low molecular weight plasticizing compounds to one block of diblock copolymers to form supramolecular comblike blocks leads to hierarchical self-assembly at the block copolymer (long) and amphiphile (short) length scales, in which lamellar-in-lamellar order and the related phase transitions have previously been shown to allow thermal switching of electrical and optical properties [Science 1998, 280, 557; Nat. Mater. 2004, 3, 872]. In this work other hierarchies and phase transitions are systematically searched, a particular interest being hierarchies containing gyroid structures and the related order−order transitions. Polymeric supramolecular comb−coil diblock copolymers consisting of a polystyrene (PS) coillike block and a supramolecular comblike block based on poly(4-vinylpyridine) (P4VP) are used, where the pyridines are either directly hydrogen bonded with 3-pentadecylphenol (PDP), i.e., PS-block-P4VP(PDP)1.0, or first protonated with methanesulfonic acid (MSA) and then h...

Violation of the Wiedemann-Franz law in a single-electron transistor.

Abstract: We study the influence of Coulomb interaction on the thermoelectric transport coefficients for a metallic single-electron transistor. By performing a perturbation expansion up to second order in the tunnel-barrier conductance, we include sequential and cotunneling processes as well as quantum fluctuations that renormalize the charging energy and the tunnel conductance. We find that Coulomb interaction leads to a strong violation of the Wiedemann-Franz law: the Lorenz ratio becomes gate-voltage dependent for sequential tunneling, and is increased by a factor 9/5 in the cotunneling regime. Finally, we suggest a measurement scheme for an experimental realization.

Reactions of methyl heptanoate hydrodeoxygenation on sulphided catalysts

Abstract: Reactions of methyl heptanoate on sulphided NiMo/γ-Al 2 O 3 and CoMo/γ-Al 2 O 3 catalysts in gas and liquid phases were investigated in detail. Experiments with heptanol and heptanoic acid were carried out in support of the conclusions. Hydrodeoxygenation (HDO) of the ester produced C 7 and C 6 hydrocarbons. Alcohols, aldehyde, carboxylic acid and ethers were formed as intermediates. In addition, a few sulphur-containing compounds were formed as intermediates and they led to desulphurisation of the catalysts. The reactions of the ester and the intermediates are explained in terms of hydrogenation and acid-catalysed reactions such as hydrolysis, esterification and dehydration. The E 2 elimination and S N 2 nucleophilic substitution mechanisms are proposed to play a role in the reactions. HDO and hydrogenation activities were higher on the NiMo catalyst than the CoMo catalyst. The NiMo catalyst might thus seem to be preferred for the conversion of aliphatic esters, alcohols and carboxylic acids. According to the proposed reaction scheme, however, hydrogen consumption will be greater with this catalyst.

Supramolecular Materials Based On Hydrogen-Bonded Polymers

Abstract: Combining supramolecular principles with block copolymer self-assembly offers unique possibilitiesto create materials with responsive and/or tunable properties. The present chapter focuses on supramolecularmaterials based on hydrogen bonding and (block co-) polymers. Several cases will be discussed where theself-assembled nanostructured morphology can be easily tuned using composition as the natural variable.A large body of the material reviewed concerns hydrogen-bonded side-chain (block co-) polymers. Sidechains both with and without mesogenic units are discussed. Frequently the thermoreversibility of the hydrogenbonds allows for responsiveness of material properties to external stimuli such as temperature, pH, andelectromagnetic fields. Temperature-dependent photonic bandgap, temperature-dependent proton conductivity,pH-erasable multilayers, temperature-induced volume transitions, and fast AC electric field-induced orientationalswitching of microdomains are the main examples.