Ib Johannsen

Surface morphology of PS-PDMS diblock copolymer films

Abstract Spin coated thin films (∼400 A) of poly(styrene)–poly(dimethylsiloxane) (PS–PDMS) diblock copolymers have been investigated using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy. Surface segregation of the poly(dimethylsiloxane) blocks was studied for five diblock copolymers which ranged in molecular weight from 7 kg/mol to 500 kg/mol. The films were annealed above and below the highest glass transition temperature of the two polymer blocks but below the order–disorder transition temperature. Information concerning the chemical in-depth distribution of the films was extracted by use of peak shape analysis of the X-ray Photoelectron Spectra via the Tougaard Method. The amount of dimethylsiloxane in the uppermost part of the films was quantified as a function of annealing time and temperature. For annealing above the PS glass transition temperature, surface segregation of the dimethylsiloxane chain-ends occurs for all the studied PS–PDMS diblock copolymers. At room temperature, surface segregation takes place only when the amount of dimethylsiloxane in the diblock copolymers is small.

Chemistry of TTF. Easy synthesis of TTF and selective synthesis of unsymmetrically substituted TTFs

Abstract A low cost, easy to perform synthesis of TTF has been developed together with a new Wittig type reaction for preparation of unsymmetrical TTFs.

The geometry and structural properties of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,­mn]pyrene system in the cationic state. Structures of a planar organic cation with various monovalent and divalent anions

The geometry of the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrene system in the cationic state was established by X-ray structural resolution of the salts formed between the cation and various anions. The geometry was found to be planar for the 4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium and 2,6,10-tri(tert-butyl)-4,8,12-trioxa-4,8,12,12c-tetrahydrodibenzo[cd,mn]pyrenylium cations with the monovalent anions I(-), BF(4)(-), PF(6)(-), AsF(6)(-), HNO(3).NO(3)(-) and CF(3)SO(3)(-), and the divalent anions S(2)O(6)(2-) and Mo(6)Cl(14)(2-). The salts were found to crystallize in distinct space groups following a characteristic pattern. Mixed cation-anion stacking resulted in space groups with high symmetry: Pbca in three cases and R3;c in one; a temperature study of the latter was made at ten different temperatures. The formation of dimers of anions and cations resulted in lower-symmetry space groups, mainly monoclinic (P2(1)/n, P2(1)/c and C2/c), but also P1;.

Morphology evolution of polycarbonate–polystyrene blends during compounding

Abstract The morphology evolution of polycarbonate–polystyrene (PC/PS) blends during the compounding process in three blending methods of industrial relevance, namely melt blending, re-melt blending in a twin-screw extruder and tri-melt blending in an injection-moulding machine, was investigated using scanning electron microscopy (SEM) to examine nine blend compositions. Blends were prepared at compositions where phase inversion was expected to occur according to model predictions. The experimental results were compared to the values of the point of phase inversion calculated with the semi-empirical model. The results show that the formation of co-continuous morphology strongly depends on blend composition and melt blending method, whereas the model prediction for phase inversion deviates from the experimental values. Further, we found that the initial mechanism of morphology evolution involves the formation of blades or stratifications in the continuous phase. These blades or stratifications became unstable due to the effects of flow and interfacial forces. We also found that fibre formation in the dispersed phase was favoured by higher shear rate.

Unusual structure-related magnetism in the organic conductor TSF(Ni(dmit)2)3 (tetraselenafulvalenium-tri-(bis-(4,5-dimercapto-1,3-dithiole-2-thione)nickel)-ate)

Abstract TSF(Ni(dmit) 2 ) 3 crystallizes in the triclinic space group PI with unit cell dimensions a = 5.875(1), b = 11.846(1), c = 18.873(1) A , α = 71.35(1) , β = 81.63(1), γ = 78.16(1)°. Thermopower and electrical conductivity measurements show semiconducting behaviour localized in the Ni(dmit) 2 network. At 65 K the unit cell doubles in the a direction and this feature is utilized in explaining an unusual cross-over from a Bonner-Fischer model to a simple singlet-triplet magnetic behaviour in the sheets of weakly interacting TSF cation radicals.

The Crystal Structure of 1,6-Dithiapyrene(DTP)-7,7,8,8-Tetracyano-P-Quinodimethane(TCNQ)

Abstract The crystal structure of the charge-transfer complex between 1,6-dithiapyrene(DTP) and 7, 7,8,8-tetracyano-p-quino-dimethane(TCNQ) is reported. The structure correlates well with the observed physical properties.

New π-Electron Donors

Abstract The synthesis of a series of new donor molecules, 1,6-dioxa-pyrenes, is reported. Also reported is a series of dimeric TTF systems. For the dimeric TTF structures the implications for the Fermi surface in 1:1 donor-acceptor salts are discussed. Preliminary results for a few new conducting salts derived from the dimeric TTFs are given.

Synthesis and Properties of Trimethyl-TSF Containing Alloys of the TMTSF2, Family

Abstract Cation-radical salts of the general formula (TriMTSFzTMTSF1-z) 2 (X = PF6, Clo4, z ranging from 0 to 0.3) were isostructural. The incorporation of TriMTSF resulted only in minor changes in the transport properties, but the superconducting ground state was completely suppressed.

Corbienes and dioxapyrenes — new weitz-type donors

Abstract Corbiene and 1,6-dioxapyrene, which are two new oxygen containing donor molecules, have been synthesized, and their electrochemical properties have been investigated.

A novel exchange reaction between diselenides and bis(N,N-dialkylselenocarbamoyl)selenides. Application in the synthesis of tetraselenafulvalene(TSF)

A high yield synthesis of tetraselenafulvalene (TSF) involving a novel acid catalysed exchange reaction between diselenides and bis(N,N-dialkyselenocarbamoyl)selenides is reported.