Thomas H. Spurling

Forces between adsorbing walls: Monte Carlo calculations

Abstract A grand ensemble Monte Carlo calculation of the force between two adsorbing walls separated by a Lennard-Jones liquid has been made. At separation distances of between two to five molecular diameters the force shows oscillations with a period of approximately one molecular diameter.

Tacticity of Poly(Methyl Methacrylate). Evidence for a Penpenultimate Group Effect in Free-Radical Polymerization

The tacticity of poly(methyl methacrylate ) prepared by free-radical polymerization has been determined by analysing the carbonyl region of the 13C n.m.r . spectrum. This analysis demonstrates that the addition of poly(methyl methacrylyl ) radical to methyl methacrylate in benzene at 60°C is subject to a significant penpenultimate unit effect. The probability of forming a meso dyad is some 20% less if the preceding dyad in the chain is also meso . The polymerization (60°C, benzene) is described by the following parameters P(m) = 0.202, P(m|m) = 0.159, P(r | m) = 0.212.

'I2-doping' of 1,4-polydienes

Abstract The discovery, in 1988, that “iodine-doped” rubber can conduct electricity attracted a great deal of interest [1,2]. However, it also generated some fundamental questions [2]: First, what is the mechanism from which the conductivity of “I 2 -doped” rubbers arises? Second, why does cis-1,4-polybutadiene not become electrically conductive by “I 2 -doping”, but its trans-conterpart does? Third, what is the effect of “I 2 -doping” and conductivity in the rubber component on rubber-containing conducting composites and/or copolymers? We have previously demonstrated that “I 2 -doping” of cis-1,4-polyisoprene produces conjugated sequences of unsaturated double bonds in the polymer backbone, which confer conductivity. Recently, we have found that “I 2 -doping” of cis-1,4-polybutadiene, unlike the trans-isomer, does not lead to the formation of conjugated sequences at room temperature — a finding which leads to the formation of conducting patterns through patterned photoisomerization of cis-1,4-polybutadiene films followed by “I 2 -doping”. We have also observed, for the first time, the occurrence of “I 2 -doping” of the polyisoprene component in polyisoprene-polyacetylene copolymers.

PCILO calculation of intermolecular energies: The water dimer

Abstract The PCILO (perturbative configuration interaction using localized orbitals) method for approximating the electronic structure of molecules has been used with some success for calculating intramolecular interactions in large molecules where intramolecular hydrogen bonding is involved. In this note we show that the PCILO method may be used to calculate the energy of interaction between two water molecules in selected configurations.

Mode of action of DDT analogues: molecular orbital studies

Neues Verfahren mittels Molekularorbital-Berechnung zur Vorausermittlung der chemischen Konfiguration und Wirksamkeit von Insektiziden vom Typ des DDT.

WATER PURIFICATION WITH MAGNETIC PARTICLES

CSIRO (Commonwealth Scientific and Industrial Research Organization) has for some years carried out research into more efficient ways of purifying water and wastewater. More intensive processing has been achieved by the use of finely divided solid reagents which can be regenerated and reused. The age-old problem of quickly separating the very small particles of loaded reagent from the accompanying liquid has been solved by utilizing a magnetic reagent in the form of magnetite, Fe3O4. A water clarification process is fully developed for the production of potable supplies from low quality ground and surface waters, with five plants in operation or under construction in Australia, the United Kingdom and Taiwan. The method has been extended to the removal of heavy metals from tailings dams, which has also reached full-scale with a plant near Canberra, to other industrial effluents, and more recently to sewage treatment. Successful pilot plant studies of the latter in Melbourne and Sydney have led to the decision to carry out a large-scale trial at Malabar, near Sydney.

Symmetry adapted perturbation theory of intermolecular potentials. The helium–helium interaction

The use of symmetry adapted perturbation theory to calculate intermolecular potentials in the important intermediate region is explored. A scheme is suggested which gives both the correct long range limit and the correct wavefunction symmetry order by order. A discussion of the accuracies of first order energies determined from approximate wavefunctions is given together with an approximate treatment of the second order energy. Finally, the overall potential obtained from this scheme for He2 is shown to be in good agreement with recent semi-empirical and variationally determined potentials.

Morpheus: a conformation-activity relationships and receptor modeling pakage

Our molecular modeling software package, MORPHEUS, allows the study of the interactions between biologically active molecules and their receptors. The package is capable of exploring the multidimensional conformational space accessible to each molecule of the data set under study. By specifying distance constraints or hypothetical receptor binding points, the package is able to filter the biologically accessible conformations of each active compound and deduce a three-dimensional model of the binding sites consistent with the properties of the agonists (or antagonists) under scrutiny. The electrostatic potentials in the environment of a putative binding site can also be investigated using the MORPHEUS package. The molecular modeling module CRYS-X, which is written in FORTRAN 77 for IBM PC machines, is capable of building, displaying and manipulating molecules.

Kinetic simulation of polymerization involving termination by reversible chain transfer

Numerical integration has been used as a means of simulating the title polymerization so that the variation of molecular weight and molecular weight distribution with reaction time (conversion) can be evaluated. The time/conversion dependence of the polydispersity (R) has been evaluated as a function of the relative magnitude of the rate constants associated with the initiation/termination equilibria . It is shown that the short term behaviour of R and the rate of approach to the value (R = 4/3) predicted by the steady state treatment have a marked dependence on the choice of rate constants.

A Numerical Approach to the Estimation of Reactivity Ratios: Application to the Styrene-DMAEMA System

Abstract The reactivity ratios for the styrene dimethylaminoethyl methacrylate (DMAEMA) copolymerization have been determined by accurate experimental procedures. The experimental results were analyzed using a completely numerical procedure developed from the equations of Skiest. The results obtained differ significantly from those previously published.