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In order to determine the chemical composition distribution (CCD) of styrene-butadiene copolymers, gradient polymer elution chromatography has been performed. The separation is mainly based on differences in solubility among the copolymer molecules with different chemical composition. The solubility of a copolymer is dependent on the following parameters: temperature, type of solvent/non-solvent mixture, molecular mass of the polymer and the chemical composition of the polymer. The resolution of the gradient polymer elution chromatographic separation and the molecular mass dependency are influenced by the solvent/non-solvent combination. In order to obtain a reliable separation according to chemical composition, the differences in solubility must be sufficiently high and the molecular mass dependence must be negligible. In order to separate styrene-butadiene copolymers, synthesized by emulsion polymerization, a tetrahydrofuranacetonitrile gradient was used. After calibration of the chromatographic system with styrene-butadiene copolymer standards, the CCD of styrene-butadiene copolymers could be calculated.

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The acceptor activity of Cu and Ni and their diffusion in germanium have been investigated. Their acting as acceptors as well as recombination centers gives reason to believe that impurity atoms are placed substitutionally in the lattice. However, the value of 10 -5 cm~/sec of the diffusion constant makes it likely that the diffusion goes interstitially. This leads to the concept of an equilibrium existing between substitutional and interstitial atoms. The fact that the diffusivity is dependent on the range of diffusion can be explained qualitatively on the basis of the picture given above.