Polymer Journal

Raman, Rakesh; Deopura, Basanti L; Varma, Dharmendra S; Gupta, Vishambher D

doi: 10.1295/polymj.9.115pmid: N/A

Temperature-dependent small-angle X-ray scattering from polyethylene is analysed using a correlation function technique. It is found that the correlation function gives two maxima corresponding to long periods of 163 A and 205 A at room temperature. These must correspond to different morphological structures. These long periods remain almost constant up to the crystallization temperature and after that they merge into a single long period which increases with increasing temperature.

Okada, Tadashi; Ikushige, Tetsuo

doi: 10.1295/polymj.9.121pmid: N/A

The high-resolution 1H-NMR spectra of poly(ethylene—vinyl acetate) with low vinyl acetate content were measured by the use of tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-1,4,6-octanedionato)europium(III) as a shift reagent. As a result, the peak assigned to the acetate methyl protons was split into a triplet, and the peak assigned to the methine proton was split into a quintet and a broad peak. These split peaks were tentatively assigned to the acetate methyl and the methine protons of the central vinyl acetate unit in the triad sequences, respectively. Since the samples were determined to be random copolymers from their 1H-NMR measurements in benzene-d6, the triad concentrations were calculated by means of the random copolymerization theory. These calculated concentrations were compared with the observed concentrations for the above split peaks in the acetate methyl and methine proton signal, and the former were in close agreement with the latter.

Inoue, Yoshio; Konno, Tetsuo; Nakajima, Katsumi

doi: 10.1295/polymj.9.127pmid: N/A

The variation, as a function of temperatute, of the carbon-13 spin-lattice relaxation time of individual carbons of poly(2-vinylpyridine) in solution was measured and the molecular motion was analysed quantitatively. The motion of the polymer can be characterized by three contributions: namely, a segmental motion and two kinds of internal rotation of the pyridine ring. The temperature dependence of the rate of the internal rotation revealed a transitional change at about 25°C, while that of the segmental motion changed linearly. It is suggested that the internal rotation of the pyridine ring is interrupted by steric hindrance, which is probably due to a repulsive interaction between the hydrogen atoms in the pyridine ring and the methine group and by a formation of hydrogen bonding at lower temperatures. Above the transition temperature, the thermally activated motion overcomes such hindrances and the pyridine ring rotates more freely.

Iizuka, Eisaku; Kondo, Yoshiyuki; Ukai, Yoshiro

doi: 10.1295/polymj.9.135pmid: N/A

Liquid crystal structures which are a collection of molecular clusters have been found in concentrated solutions of sodium salt of poly(glutamic acid) by means of polarizing micrograph, scattering of laser light, infrared absorption, X-ray diffraction, circular dichroism, and some other physical methods. This polymer undergoes a coil–helix transition at a certain polymer concentration that depends on the temperature, even at slightly alkaline pHs, and eventually becomes liquid crystalline. With the addition of 50-%(v/v) dioxane, helical polymers are separated as coacervate and show similar structures.

Matsubayashi, Hajime; Chatani, Yozo; Tadokoro, Hiroyuki; Tabata, Yoneho; Ito, Wataru

doi: 10.1295/polymj.9.145pmid: N/A

The copolymer obtained by radiation-induced copolymerization of hexafluoroacetone with ethylene at −78°C was examined by X-ray diffraction. The crystal data are: orthorhombic, P212121, a=10.63 A, b=8.00 A, c(fiber axis)=8.01 A, and two polymer chains pass through the unit cell. The copolymer was revealed to have an alternating structure of hexafluoroacetone and ethylene units. The molecular chain forms a (2/1) helix of essentially (TTTC)2 conformation. The internal rotation angles are as follows:

Kitano, Toshiaki; Fujimoto, Teruo; Nagasawa, Mitsuru

doi: 10.1295/polymj.9.153pmid: N/A

The anionic polymerization of tert-butyl acrylate was studied to determine the experimental conditions for preparing poly(acrylic acid) having narrow molecular weight distributions. If the monomer is carefully purified, the monomer can be anionically polymerized with n-butyllithium in tetrahydrofuran at −78°C. The propagation proceeds by living mechanism, though side reactions seem to occur at the initiation stage. The polymer obtained can be hydrolyzed with hydrobromic acid without degradation.

Yokoyama, Yoshio; Arai, Makoto; Nishioka, Atsuo

doi: 10.1295/polymj.9.161pmid: N/A

Poly(γ-benzyl L-glutamate) in a concentrated methylene chloride solution is in a liquid crystalline state. The solvent signal of this solution is a doublet due to magnetic dipole—dipole interactions. Separation of the doublet varies with residence time of the sample in the magnetic field after insertion in the NMR probe or after changing the direction of the applied field. This is attributed to the time dependence of the orientation or reorientation of molecules in the magnetic field.The time dependent phenomena were observed by 1H-FT-NMR and a floppy disk drive system. That is, after changing the direction of the applied field the peak height of the upfield one of the methylene chloride doublets first decreases gradually relative to the downfield one, and still later the peak height of the upfield one increases, and finally both peaks become of equal height. This is interpreted through the anisotropy of the diamagnetic susceptibility Δχ for oriented nematic liquid crystals. The theory is given and the potential for obtaining structural information about nematic liquid crystals of polypeptide is discussed.

Ogata, Naoya; Hosoda, Yoshikazu

doi: 10.1295/polymj.9.167pmid: N/A

Epoxy and formal derivatives of tartarate were found to be easily subjected to polycondensation reactions with hexamethylenediamine (HMD) in solutions under mild conditions and linear polyamides having epoxy or formal groups were obtained in a quantitative yield. The polycondensation reaction of epoxy succinate with HMD was influenced by solvents and a competitive reaction between a nucleophilic attack of amine to ester and epoxy groups was also influenced by solvents.Thus, a cross-linked polyamide was obtained from epoxy succinate and HMD. On the other hand, a linear polyamide was obtained from formal tartarate and HMD. The polyamide from formal tartarate and HMD suffered a cross-linked reaction among the formal groups on heating.

Iizuka, Eisaku

doi: 10.1295/polymj.9.173pmid: N/A

The concentrated solutions of sodium salt of deoxyribonucleic acid have been observed under crossed polaroids and tested by means of the small-angle laser light scattering, the ultraviolet and infrared absorptions, the X-ray diffraction, the circular dichroism, and some other physical methods. The molecules of this poly-nucleotide aggregate to form rod-like assemblies (molecular clusters) at a certain polymer concentration and eventually form liquid crystalline structures. These liquid crystals are very similar to those found in the concentrated aqueous solutions of deoxygenated sickle-cell hemoglobin or of sodium salt of poly(glutamic acid).

Kusanagi, Hiroshi; Tadokoro, Hiroyuki; Chatani, Yozo

doi: 10.1295/polymj.9.181pmid: N/A

An energy minimization method for seeking stable crystal structure in terms of the nonbonded repulsive energy alone was derived. The variable parameters are molecular positions and their internal coordinates; the unit cell dimensions and the space group are fixed to those obtained by X-ray analysis. By starting from the crystal structure models composed of uniform helical chains for polyisobutylene, poly(ethylene oxide), and isotactic polypropylene, the present method gave energetically stable structures which are very close to those determined by X-ray analyses. Furthermore, a constrained least-squares method was derived, in which the intra- and intermolecular repulsive energies were taken into account in addition to the differences of the observed and calculated structure factors. This constrained least-squares refinement was successfully applied to the crystal structure analysis of isotactic poly(4-methyl-1-pentene).