Conformational characteristics of poly(trimethylene sulfide) (PTMS) have been investigated by a rotational isomeric state analysis of ab initio molecular orbital calculations and 1 H and 13 C NMR experiments for a monomeric model compound, 1,3-bis(methylthio)propane, and the characteristic ratio and dipole moment ratio of the unperturbed PTMS chain. Both C-S (the first-order interaction energy, -0.30 kcal mol -1 ) and C-C (-0.58 kcal mol -1 ) bonds prefer the gauche conformation. For comparison, conformational analysis of the corresponding polyether, poly(trimethylene oxide), has also been carried out. The C-O (+0.97 kcal mol -1 ) and C-C (-0.47 kcal mol -1 ) bonds show trans and gauche preferences, respectively. These results are consistent with the conformational stabilities predicted by the natural bond orbital analysis on model compounds of poly-(ethylene sulfide) (PES) and poly(ethylene oxide). Without the strong S‚‚‚S repulsion, therefore, the C-C bond adjacent to the C-S bond exhibits its inherent gauche preference. Without the (C-H)‚‚‚O attraction, the ethereal C-C bond is subject to the attractive gauche effect. For representative polysulfides and polyethers, relationships between conformations in the Θ and crystalline states and thermal properties have been investigated. Even in the Θ and crystalline states, the polymers mostly keep the conformational preferences found for their small model compounds; as an exception, poly(propylene sulfide) and poly(propylene oxide), having a methyl side chain, crystallize to adopt the metastable all-trans conformation. On average, the configurational entropy of the polymers amounts to 80-90% of entropy of fusion, and the configurational energy change between crystalline and molten states accounts for ca. 30% of enthalpy of fusion. Of the polymers investigated here, PES has an exceptionally high melting point; the dipole-dipole interaction in the PES crystal was evaluated to be -1.0 kcal mol -1 (ca. 30% of the enthalpy of fusion), thus being the source of the thermostability.

Conformational characteristics, solution (melt) properties, and thermal properties of polyselenoethers [-(CH2)ySe-]x ( y=1, 2, and 3) have been revealed by the rotational isomeric state analysis of ab initio molecular orbital calculations and (1)H and (13)C NMR experiments for monomeric model compounds and compared with those of typical polyethers and polysulfides. The comparative results are summarized here as correlations in conformation among model compounds and unperturbed and crystalline states of the polymers, and thermal properties of the polymer crystals are discussed in terms of intramolecular and intermolecular interactions. By ab initio molecular orbital calculations under periodic boundary conditions, helical structures of poly(methylene oxide), poly(methylene sulfide), and poly(methylene selenide), and the crystal structure of poly(ethylene selenide) have been optimized, and their electronic structures have been predicted. A systematic methodology to predict and characterize up to higher-order structures and various physical properties of polymers incorporated in different phases has been attempted to be developed.

Noncollinear acoustooptic tunable filters using TeO(2) crystals are described. An anisotropic Bragg diffraction is studied applying simple design expressions to a tilt type in which an acoustic wave is launched a little off the [110] axis. Tuning property, filter bandwidth, angular aperture, required acoustic power, deflection angle, divergenceless configuration, and rapid spectrum scanning have been discussed. These filter properties have been confirmed with measurements using three kinds of filter devices: a basic type, an acoustically enhanced type, and a large angular aperture type. A 5-A bandwidth at 4000 A was obtained by slow scanning. A 32-A separation at 4000 A was observed by a rapid scanning of 0.5 msec throughout the visible region with an extremely low electric drive power.

A new glass, composed of TeO2, was found to be well suited to acousto-optical devices. It exhibits a high figure of merit: Me(p2n6/ρv3) = 23.9×10−18 sec3/g and has very good optical qualities with regard to visible light.

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