| Research Abstract |
In this project, we have developed an advanced rotational isomeric state (RIS) scheme for molecular design of organic and polymeric materials through the following three subjects.
(1) Six dimeric model compounds of poly (propylene oxide), having different configurational sequences, were prepared, and investigated by carbon-13 NMR.The observed chemical shifts, assigned experimentally to the component carbon atoms, were well reproduced by the RIS scheme combined with substituent effects. The agreement between theory and experiment shows the validity of the conformational energies used in the calculations, the presence of the intramolecular (C-H)…O attraction, and the applicability of the RIS scheme to chemical-shift evaluation.
(2) Unperturbed chain dimensions of poly (methyl n-propylsilane), poly (di-n-butylsilane), and poly (di-n-hexylsilane) were evaluated by static light scattering and size-exclusion chromatography-multichannel laser light scattering. For individual polymers, conformational energies including interactions of both main and side chains were determined from molecular dynamics simulations. The observed characteristic ratios were well reproduced by the RIS scheme using the conformational energies thus determined. Thus, we have developed a method for conformational analysis of polymers with long side chains.
(3) Conformational and orientational characteristics of chain molecules such as n-alkanes and ethers dissolved in nematic solvents and amphiphilic molecules incorporated in hexagonal, lamellar, and reversed hexagonal aggregates have been investigated. Deuterium NMR quadrupolar splittings and proton-proton dipolar couplings were simulated by a combined use of the RIS scheme and the maximum entropy method. We have established a methodology for conformational analysis of chain molecules in anisotropic fields.
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