Synthesis and characterisation of four- and six-membered P-Se heterocycles

The preparation, spectroscopic characterisation and crystal structures of [FcP(mu-Se)Se]2, [FcP(mu-Se2)Se]2 and [PhP(mu-Se2)Se]2 are reported. Crystallographic data reveal planar four-membered PSePSe and skewed six-membered P2Se4 rings, respectively, in all cases with trans arrangement of organic substituents and exo selenium atoms. Whilst stable at room temperature in solid state, NMR data suggest the six-membered rings of both the ferrocenyl and phenyl compounds decompose in the solution with loss of red selenium, forming PSe2PSe five-membered rings.     

The Maxwell-Contact

In multibody systems, two alternative approaches exist to compute contact forces between bodies. The unilateral constraint contact and the unilateral regularized contact do not take into account the influence of the deformation due to other contacts on a body using rigid body dynamics. In this paper, a third alternative, i.e. the Maxwell-Contact, is derived coupling the deformations of different contacts on one body quasi-statically. An academic example validates the fundamental properties of the contact model and the application in a simulation of a pushbelt CVT shows improved results. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ion etching of polymers

Semi-crystalline and amorphous polymers were etched using high energy ions. It was found that two basic surface patterns exist. But those patterns do not reflect the inner structure of the etched polymer. Instead the modulation of the surface is formed by a characteristic dependence of the etching process on the angle of incidence of the ions. Rows, found on the surface of uniaxially oriented polymers, can be explained by surface diffusion processes.     

Strangeness exchange reaction on nuclei

Population of hypernuclear states has been observed in recoiless Λ production of the strangeness exchange reaction (K^?, π^?) on ⁹Be, ¹²C, ¹⁶O, ³²S and ⁴⁰Ca.     

Rubber elasticity and network structure

By defining stretching-invariant subunits of deformation in terms of the van der Waals model it is shown that the density of these subsystems can be smaller than the density of the cross-links. This is observed in short-chain networks with rigid cross-linkages, where due to the broad chain length distribution, very short and therefore stiff network chains appear. It is in any case possible to relate the modulus to the weight fraction of the cross-linking agent if the production of chemical cross-limits per agent molecule is properly defined. The stress-strain behavior of the rubbers can then be fully described within the total range of strains embracing also the upturn at largest elongation.Moreover, on the use of a thermodynamics of swelling of van der Waals networks, a set of swelling experiments drawn from literature can be described: the key assumption is that configurational exclusion effects within the swollen short-chain network must be accounted for. In the case of swelling with flexible molecules there is a need for further empirical modification of the thermodynamical formalism indicating that the configurational abilities within these swollen networks seem also to depend on the relative ratio of the network chain length related to the length of the linear solvent molecules.Dedicated to Prof. Dr. R. Kosfeld on the occasion of his 60th birthday.     

The semi-phenomenological model of antiferroelectricity in chiral smectic liquid crystals I. The structure of short pitch modes and a thermodynamical approach

The development of the model of short pitch modes for ferro-, antiferro- and ferri-electric chiral smectic liquid crystals is presented. Prediction of the structures of the subphases is made. The pure short pitch mode having an n-ray star structure of the n-layers of the unit cell appears to possess antiferroelectric properties. Ferrielectricity is assumed to arise as a result of the coexistence and interaction of the short pitch mode with a long pitch helix. Corresponding polarizational properties and fine structure of the peaks of the resonant X-ray scattering from such structures are calculated.     

The maximum melting temperatures in strain-crystallized van der waals networks

A theory of strain-crystallization of random networks comprised of stereoregular chains is developed. The crosslinks are assumed to be expelled from crystal cores. For this reason, the rubber is considered to be represented as a random eutectoid copolymer, the thermodynamics of strain crystallisation of which is described by the use of the van der Waals model of networks. The strain dependence of the maximum melting temperatures, the degree of crystallinity and the average thickness of the crystallites calculated are shown to be in fair accord with experimental data.Dedicated Prof. Dr. R. Bonart on the occasion of his 60th birthday.     

Thermodynamische (maximale) Schmelzpunkte von oligomeren und polymeren Einstoff- und Mehrstoffsystemen

Colloid and Polymer Science - Mit Hilfe des Gittermodells von Flüssigkeiten wird in Anlehnung an bekannte Ansätze die Entropie von ideal athermischen polymeren Vielkomponentenmischungen...