Conformational characteristics of poly(3-hydroxyvalerate) (P3HV) and structure-property relationships of P3HV and poly(3-hydroxybutyrate).

Conformational analysis of biosynthetic and biodegradable poly(3-hydroxyvalerate) (P3HV), an analog of poly(3-hydroxybutyrate) (P3HB), was performed. The only structural difference between the two polymers consists in the side chain, which is either methyl (P3HB) or ethyl (P3HV). Molecular orbital calculations and NMR experiments were conducted on a monomeric model compound to determine the bond conformations of the main and side chains of P3HV.

Conformational characteristics and conformation-dependent properties of poly(ε-caprolactone).

Structures and properties of isolated and crystalline poly(ε-caprolactone) (PCL) chains have been investigated. molecular orbital (MO) calculations were conducted for methyl 6-acetoxyhexanoate (MAH), a model compound of PCL, to yield Gibbs free energies of all its existent conformers. Bond conformations of its seven bonds corresponding to the repeating unit of PCL were calculated therefrom; two C-C bonds close to the ester group show preferences owing to intramolecular C-H⋯O attractions, and the other five prefer forms.

Molecular Design of Aromatic Polythionoesters.

As an example of molecular design of new polymers, structures and properties of poly(ethylene thionoterephthalate) (PET[S]) and the related polymers have been predicted from calculations of ab initio molecular orbital (MO) theory, rotational isomeric state (RIS) scheme, and periodic density functional theory (DFT). The MO calculations were confirmed by NMR experiments and introduced to the RIS scheme for PET[S] to yield its configurational properties, which are compared herein with those of analogous polyester, polythioester, and polydithioester. Configurational properties of randomly thiono-substituted poly(ethylene terephthalate) (PET), PET[S O ], were also evaluated as a function of sulfidity ().

Computational Characterization of Nylon 4, a Biobased and Biodegradable Polyamide Superior to Nylon 6.

This study is an attempt to develop a theoretical methodology to elucidate or predict the structural characteristics and the physical properties of an isolated polymeric chain and its crystalline state precisely and quantitatively. To be more specific, conformational characteristics of a biobased and biodegradable polyamide, nylon 4, in the free state have been revealed by not only ab initio molecular orbital calculations on its model compound but also nuclear magnetic resonance experiments for the model and nylon 4. Furthermore, the crystal structure and solid-state properties of nylon 4 have been elucidated by density functional theory calculations with a dispersion force correction under periodic boundary conditions.

Crystal structure of butane-1,4-diyl bis-(furan-2-carboxyl-ate).

The asymmetric unit of the title compound, CHO, a monomeric compound of poly(butyl-ene 2,5-furandi-carboxyl-ate), consists of one half-mol-ecule, the whole all- mol-ecule being generated by an inversion centre. In the crystal, the mol-ecules are inter-connected C-H⋯O inter-actions, forming a mol-ecular sheet parallel to (10). The mol-ecular sheets are further linked by C-H⋯π inter-actions.

Crystalline Moduli of Polymers, Evaluated from Density Functional Theory Calculations under Periodic Boundary Conditions.

A theoretical methodology based on quantum chemistry to calculate mechanical properties of polymer crystals has been developed and applied to representative polymers. By density functional theory calculations including a dispersion force correction under three-dimensional periodic boundary conditions, crystal structures of poly(methylene oxide) (PMO), polyethylene (PE), poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate) (PTT), and poly(butylene terephthalate) (PBT) were optimized and their mechanical properties, such as crystalline moduli and linear and volume compressibilities, were calculated. The optimized crystal structures were proved to be fully consistent with those determined by X-ray and neutron diffraction.

Crystal structures of 2-(benzene-carbo-thio-yloxy)ethyl benzene-carbo-thio-ate and 2-(benzene-carbo-thio-yloxy)ethyl benzoate.

The title compounds, CHOS and CHOS, which are monomeric models (models and ) for a polythio-noester and a poly(ester--thio-noester), respectively, crystallize in the space group 2/ and are isostructural with each other. The mol-ecule in each crystal is located on an inversion centre and has an all- structure. The asymmetric unit comprises one half-mol-ecule.

Structure-Property Relationships of Poly(ethylene carbonate) and Poly(propylene carbonate).

Conformational characteristics of poly(ethylene carbonate) (PEC) and poly(propylene carbonate) (PPC) have been revealed via molecular orbital (MO) calculations and nuclear magnetic resonance (NMR) experiments on model compounds with the same bond sequences as those of the polycarbonates. Bond conformations derived from the MO calculations on the models were in exact agreement with those from the NMR experiments. Both PEC and PPC were indicated to adopt distorted conformations including a number of gauche bonds and cover themselves with negative charges, thus failing to form a regular packing and remaining amorphous.

N,N'-(Propane-1,3-di-yl)dibenzo-thio-amide.

The title compound, C17H18N2S2, exhibits a trans-trans-trans-gauche(+) (tttg (+)) conformation with regard to the NH-CH2-CH2-CH2-NH bond sequence. In the crystal, mol-ecules are connected by N-H⋯S=C and C-H⋯S=C hydrogen bonds, forming a herringbone arrangement along the c-axis direction. The two thioamide groups make dihedral angles of 43.

N,N'-(Ethane-1,2-di-yl)di-benzene-carbo-thio-amide.

The title compound, C16H16N2S2, adopts a gauche (+)-gauche (+)-gauche (+) (g(+)g(+)g(+) ) conformation in the NH-CH2-CH2-NH bond sequence. In the crystal, mol-ecules are connected by pairs of N-H⋯S=C hydrogen bonds and C-H⋯π inter-actions, forming a tape structure along the c-axis direction.

Butane-1,4-diyl bis-(benzene-carbodi-thio-ate).

The title compound, C18H18S4, which lies on an inversion center, adopts a trans-gauche (+)-trans-gauche (-)-trans (tg (+) tg (-) t) conformation of the S-CH2-CH2-CH2-CH2-S bond sequence. In the crystal, a π-π inter-action with a centroid-centroid distance of 3.8797 (16) Å is observed.

S,S'-Butane-1,4-diyl bis-(benzene-carbo-thio-ate).

The title compound, C18H18O2S2, which lies on an inversion center, adopts a gauche (+)-trans-trans-trans-gauche (-) (g (+) tttg (-)) conformation in the S-CH2-CH2-CH2-CH2-S bond sequence. In the crystal, mol-ecules are packed in a herringbone arrangement through inter-molecular C-H⋯π inter-actions.

Ethane-1,2-diyl bis-(benzene-dithio-ate).

In the crystal structure, the title compound, C(16)H(14)S(4), is located on an inversion center and exhibits a gauche(+)-trans-gauche(-) conformation in the S-CH(2)-CH(2)-S bond sequence. The S-C=S plane makes a dihedral angle of 30.63 (17)° with the phenyl ring.

Predictive elucidation of conformational characteristics and configurational properties of poly(1-methylphosphirane) and poly(1-phenylphosphirane) as a molecular design.

Conformational characteristics and configurational properties of poly(1-methylphosphirane) (PMePP) and poly(1-phenylphosphirane) (PPhPP) have been predictively elucidated by the refined rotational isomeric state scheme coupled with ab initio molecular orbital and density functional calculations. The lone pair of the phosphorus atom adopts an sp hybrid orbital. Owing to the high s character (50%), the polyphosphiranes exhibit low proton (hydrogen) affinities, and hence the lone pair does not form any intramolecular attractive interactions with hydrogen.

Structure-property relationships of polyselenoethers [-(CH2)ySe-]x (y=1, 2, and 3) and related polyethers and polysulfides.

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.

Conformational peculiarities of alcohols incorporated in lyotropic and thermotropic liquid crystals.

Conformational characteristics of 1-butanol incorporated not only in hexagonal and lamellar aggregates formed by a lyotropic liquid crystal composed of sodium octanoate, 1-butanol, and water but also in a thermotropic liquid crystal, 4'-methoxybenzylidene-4-n-butylaniline (MBBA), have been investigated from 2H NMR quadrupolar splittings of the perdeuterated and partially deuterated compounds. In the lyotropic phases, 1-butanol shows strong trans preferences and renders itself extended, and octanoate decreases the trans fraction toward the methyl terminal to fill the inner space of the aggregate on behalf of 1-butanol. In MBBA, 1-butanol prefers globular conformations.