The C3H62+ potential energy surface was studied by ab initio molecular orbital theory employing the 3-21G and 6-31G* basis sets and Moller-Plesset perturbation theory. The protonated allyl cation 1, which formally has two terminal cation centers, and the propylidene dication 3, which has formally both charges located at its central dimethyl-substituted carbon, have virtually the same energy at MP4/6-31G*. The relative high stability of these two isomers results from effective bishyperconjugation and crosshyperconjugation, respectively. Examples of [1,3]-H and [1,2]-CH4 sigmatropic shifts are discussed for isomeric propylene and vinyl-substituted methonium diions; a transition structure with carbon hexacoordination is involved. Both dications 1 and 3 are predicted to be observable in the gas phase. Energy evaluations are presented for the adiabatic (di)oxidations from neutral and radical cation precursors.Carbodications are increasingly common, both as species observable in solution and in the gas phase.1•2 Exciting structures are exhibited by dications in super acid media; the dehydroadamantdiyl,3 pagodane,4 and Hogeveen dications5 are illustrative. Their structures exemplify the special stabilizing properties (often uniquely) to doubly charged hydrocarbons. In contrast, structural and energetic information is very limited for the numerous doubly charged species that are now frequently observed in the gas phase.2
In an attempt to adjust the lateral density of monolayer and multilayer films of a ferroelectric liquid crystalline copolymer, blends of the copolymer were made with the corresponding mesogenic monomer unit. The monomer was chosen as the second component since it forms monolayer films which are more condensed than the copolymer and because of its miscibility with the structurally similar copolymer. Analysis of the interaction between the molecules of the mixed monolayers included II-area isothermal data, calculation of the excess AGmh, thermal dependence of isotherms, and Brewster angle microscopy. On the basis of these results, the films appear to be completely miscible over all conditions presented and the blend monolayer films are more condensed than the pure copolymer films.
A previously studied side chain liquid crystalline (LC) polymer consisting of a methacrylate backbone, ethylene oxide spacer, and methoxybiphenyl mesogenic group, was found to spread to form monolayers at the air-water interface. Further investigation showed that the polymer's film properties were less than optimum for the formation of multilayers on solid substrates. To enhance the stability of the film on the water surface, the LC polymer was mixed with two well known monolayer forming compounds. First a fatty acid, stearic acid was blended with the polymer. The resulting film appeared to have properties characteristic of the average of the two pure components, indicating no attractive interaction between the compounds. The second blend material was a polymer, poly(octadecyl methacrylate). The mixed film exhibited better monolayer film properties than either of the pure polymers with respect to stability, isotherm reproducibility and temperature dependence. Isobaric analysis of the blend isotherms, stability data, and deposition results are presented and discussed.Liquid crystalline polymers are of interest due to their self ordering capabilities, with the added advantage of greater mechanical and thermal stability over low molecular weight compounds . Our group is interested in the behavior of these compounds when they are confined to approximately two dimensions at an air/water interface. The side chain liquid crystalline polymers shown below (Figure 1) are the focus of this research and their bulk properties have been well documented (1.2.3.4.5). These polymers spread on a water surface and yield typical reproducible isotherms upon compression using a Langmuir-Blodgett (LB) trough. Figure 1. Structure of the side chain liquid crystalline polymers.
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