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Volume 51, Issue 4
Displaying 1-10 of 10 articles from this issue
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Akihiro ABE1994 Volume 51 Issue 4 Pages 213-221
Published: April 25, 1994
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSUnder the experimental conditions (-12 T) employed in the conventional NMR measurements, anisotropic molecules capable of forming liquid crystals often exhibit a nematic mono-domain with the director lying along the magnetic field. The 2H NMR technique allows us to determine the orientational erder parameter of the deuteriumlabeled bond. The magnitude of such an order parameter depends on the orientational fluctuation of the entire molecule, as wel as on the bond conformation, when internal rotations are permitted. We have proposed a 2H NMR/RIS simulation scheme which enables us to elucidate conformation of chain molecules involved in such liquid crystals. In this article, two examples are mentioned: (1) conformation of side chains flanking α-helical poly (γ-benzyl L-glutamate) (PBLG) and (2) conformlational distribution of spacers incorporated inα, ω-bis [ (4, 4′-cyanobiphenyl) oxy] alkane (CBA-n). It has been pointed out that the cooperativity along the chain is enhanced in the liquid crystalline state. The analysis has been extended to investigate the roles of these flexible chains in determining the thermodynamic properties of the system. The applicability of the MD simulation technique to these subjects is also discussed.View full abstractDownload PDF (1775K) -
Tomoyuki HAMADA1994 Volume 51 Issue 4 Pages 223-227
Published: April 25, 1994
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSAb-initio LCAO CPHF (Coupled perturbed Hatree-Fock) study was performed to calculate the longitudinal cubic hyperpolarizability of the polyacetylene and polydiacetylene oligomers. The theoretical calculation successfully reproduced the experimentally measured non-resonant THG values of the hyperpolarizabilities of the polyacetylene oligomers. The effect of the conjugation pattern on the hyperpolarizability was investigated. The hyperpolarizability of the polyacetylene oligomers was found to be larger than that of the polydiacetylene ones. We could estimate the order of the nonlinearity of corresponding polymer systems from the results of oligomer calculations. These reconfirmed the spatial locality of the process in the nonlinear optical phenomena.View full abstractDownload PDF (952K) -
Masahide TAKAHASHI, Takahiro ISHII, Shigetoshi AMIYA1994 Volume 51 Issue 4 Pages 229-235
Published: April 25, 1994
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSThe neural network method was applied to estimate theoretical Young's moduli of thermotropic copolyesters constituted from p-hydroxybenzoic acid as a main repeating unit. Theoretical Young's moduli of the copolyesters based on p-hydroxybenzoic acid, m-hydroxybenzoic acid and, 2-hydroxy-6-naphthoic acid were calculated by Treloar's method, and used to determin some parameters for the neural network system. After the neural network system was completed, Young's moduli of other samples were estimated by this system. The values obtained agreed well with calculated one's. The completed neural network system is also able to evaluate the effects of the structure parameters for Young's moduli. The neural network is thus a useful method to evaluate the correlation between the structure parameters and physical properties.View full abstractDownload PDF (973K) -
Yasushi AIKAWA1994 Volume 51 Issue 4 Pages 237-243
Published: April 25, 1994
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSTwo calculation methods which can estimate the birefringence of oriented polymers based on their structures were studied. Birefringence of polymers can be quantitatively measured by observation of the light retardation through a film which is oriented under constant load and constant draw ratio. Birefringence of completely elongated polymer chains was calculated from the anisotropy of the refractive index, which was determined from molar volume (V) and anisotropy of polarizability (P). To obtain the polarizability, two methods were tried. One came from the vector summation of bond polarizability, another was based on the result of semi-empirical molecular orbital calculation MOPAC. Both methods gave good correlation with the experimental results. The molecular orbital method had less dependence on parameters or initial geometry, but it required more calculation than the contribution method. The concept of “Cross-Planer Aromatic Group” can be a guiding principle for design of low birefringence polymers.View full abstractDownload PDF (1410K) -
Photophysical and Photochemical Processes in Model CompoundsYuichi TOKITA, Yuji INO, Akio OKAMOTO, Masatoshi HASEGAWA, Yoichi SHIN ...1994 Volume 51 Issue 4 Pages 245-250
Published: April 25, 1994
Released on J-STAGE: July 27, 2010
JOURNAL FREE ACCESSThe photoinduced intramolecular charge transfer which dominates the photochemical process of benzophenone type Polyimides was investigated in relation with the conformation and the rotational potential of the polyimide chains. With a focus upon the chain conformation around the bond between the imide ring and the aromatic ring, the most stable dihedral angle and the rotational potential were estimated based upon the quantum chemical calculation with semiempirical AM1 and ab initio STO-3G. Althogh N- (3-ethylphenyl) phthalimide has a very low rotational Potential and rotates freely, the rotational potential of N- (2, 2-diethylphenyl) phthalimide is very high and the most stable dihedral angle is 73°. Further, the possibility of intramolecular charge transfer was estimated qualitatively on the basis of molecular orbital consideration. These results coinside well with the experimental results for the photochemical reaction of model benzophenone bisimide compounds.View full abstractDownload PDF (1013K) -
Shinji ANDO1994 Volume 51 Issue 4 Pages 251-257
Published: April 25, 1994
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSRefractive indices at 589.3nm of 19 polyimides were measured using an Abbe refractometer and calculated from their Van der Waals volumes and molecular polarizabilities. The calculated refractive index (ncalc) when the packing coefficient was assumed to be 0.681 shows a linear relationship with the measured index (n) with a square correlation coefficient of 0.900. However, the slope considerably deviates from 1.0, which indicates that the molecular packing of polyimides changes according to their molecular structure. Packing coefficients (Kp) of polyimides are estimated by comparing fi with calculated parameter φ0. The molecular chains of the polyimides with high n are densely packed, and a planar structure of pyromellitic dianhydrides or ether linkages lead to high Kp. In contrast, the molecular chains of polyimides with low n are loosely packed, and trifluoromethyl groups cause a decrease of interchain interaction and a intra-chain steric hindrance that inhibits molecular packing.View full abstractDownload PDF (1189K) -
Ichiro OGURA, Takashi YAMAMOTO1994 Volume 51 Issue 4 Pages 259-263
Published: April 25, 1994
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSBy using molecular dynamics (MD) simulation of polymer under tension, we studied the mechanical properties of amorphous polymer in view of microscopic dynamics. Our model of amorphous polymethylene was a linear chain of spherical methylene segments which were placed in the basic cell by the phantom chain growth method developed by Clarke and Brown, and the constant tension MD method was adopted. The sample suffered the extremely impactive tension, and the trend of orientation could be detected through 30000 steps (143ps). We observed that the microscopic chain orientation and the macroscopic deformation occurred in some stages. The mode of the orientation was found to be closely correlated with the stages of deformation.View full abstractDownload PDF (775K) -
Kohji TASHIRO, Masamichi KOBAYASHI, Kazuyuki YABUKI1994 Volume 51 Issue 4 Pages 265-274
Published: April 25, 1994
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSNovel polymer crystals with three-dimensionally high elastic moduli have been designed through computer. calculations by cross-linking the conventional rigid-rod polymer chains such as poly (p-phenylene benzobisoxazole), poly (p-phenylene pyromellitimide), poly-p-phenylene, and polyacetylene. Thus obtained cross-linked polymer crystals have been found in some cases to exhibit the almost isotropically high Young's moduli and low linear compressibilities, the values being far beyond those of the diamond crystal.View full abstractDownload PDF (1658K) -
Akihiro AOKI1994 Volume 51 Issue 4 Pages 275-282
Published: April 25, 1994
Released on J-STAGE: July 27, 2010
JOURNAL FREE ACCESSThis report proposes the Monte Carlo simulation method for estimating the probabilities of small end-to-end distance of linear oligomers. Amounts of oyclic eligomers calculated by these probabilities have a good coincidence with the observed values especially for cyclic dimers of four kinds of aromatic polyesters.View full abstractDownload PDF (1586K) -
Akihiro AOKI1994 Volume 51 Issue 4 Pages 283-287
Published: April 25, 1994
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSThe amounts of cyclic trimer of poly (ethylene terephthalate) (PET) predicted by the RIS (rotational isomeric state) method were 1/5 to 1/10 of the obserbed value. Conformational analysis of a linear trimer of PET indicated that neighboring phenyl-phenyl ring interactions enhance the probability of small end-to-end distance and the RIS model with 1-20 nonbonded interactions give reasonable values of the formation of PET cyclic trimer. This model (with 1-20 nonbonded interaction) can be applied to calculate the mean square end-to-end distance of PET and calculated <R2> of PET (upto 30-mers) coincides with the obserbed unperturved dimension <R2>0 of PET.View full abstractDownload PDF (1208K)
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