Optical absorption and photoluminescence measurements on the title polymers, -f-Pt(PBu~), -(C-C),,,-C~C+, (m= 1, 2 ) show that there is appreciable n-electron conjugation extending through the metal sites on the chain, with a lower n-n* energy gap for the triacetylenic than for the diacetylenic compound.

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Electron diffraction and low-dose, high-resolution imaging techniques have been used to obtain structural information for a rigid-rod polyyne containing platinum atoms directly bonded into the main chain. The high-resolution images show details of the arrangement of the molecular chains into crystallites ~50 nm in diameter; dislocations and grain boundaries have also been imaged. A combination of electron diffraction and information derived from image processing of the high-resolution images indicates a unit cell in which parameters of a = 2.08 nm, c = 1.20 nm, and 90°< d < 93°have been measured and where b has tentatively been assigned as ~1.9 nm. The variations in /3 relate to improvements in the degree of orientation of the polymer chains that arise from slight stretching of the thin films.

Abstract. 2014 The extent to which near-edge structure depends upon long-range order is explored using polymeric systems, where one can vary the disposition of side-groups and the degree of crystallinity and compare the resulting spectra. Carbon K-edges for polystyrene in atactic and isotactic forms are compared; the former is amorphous and the latter crystalline. Differences between the spectra are very slight but observable, and are attributed to bond orientation effects and to interaction between closely-spaced hydrogens bonded to neighbouring benzene rings and to the backbone. The quality of the spectra collected at doses of less than 300 e-nm-2 from a few square microns compares favourably with previously published EXAFS data. Another example of near-edge structure is provided by segregated species. The case of iron segregated to boundaries in Zr-Nb alloys is of intense interest to the nuclear industry. An attempt has been made to interpret observed fine structure in terms of structure from reference intermetallic compounds. It seems that the fine structure displayed by the segregated iron is different from that displayed by pure metallic iron or by known compounds with Zr, but more akin to ZrNbFe.Microsc. Microanal. Microstruct. 6 (1995) Figure 1. A benzene ring is attached to every other carbon atom of the carbon backbone. Each carbon atom has two different bonds to which the benzene ring can be attached. In isotactic polystyrene the rings are all attached to the same side of the carbon backbone. This isomer can be produced in both amorphous and crystalline forms. In atactic polystyrene the benzene rings are distributed at random on both sides of the carbon chain, which precludes the possibility of crystallization. Polystyrene was chosen because, by comparison to many polymers, it is less sensitive to irradiation damage by an electron beam. Spectra were acquired from amorphous atactic polystyrene, amorphous isotactic polystyrene and crystalline isotactic polystyrene. The amorphous films were produced by dissolving the polystyrene in toluene and drawing out a film on a glass slide. The crystals were produced as described by Tanzawa [1] and deposited from solution directly onto commercially produced SiO films on Cu