Polymer Journal

Lagant, P; Vergoten, G; Loucheux, C; Fleury, G

doi: 10.1295/polymj.11.345pmid: N/A

The conformational properties of poly(α-L-aspartic acid) (L-Asp)n have been investigated in water, in deuterium oxide and also in the solid state, by Raman scattering. The conformational transition induced by changing the pH of the solutions has been given special attention. The spectra exhibit a mixture of different conformations. Random-coil and β-antiparallel pleated-sheet conformations exist in both acidic and ionized forms of the polyacid. In addition a local β1 helical conformation has been detected in the ionized form. The α helical conformation appeared as the acidic form only.

Yagi, Toshiharu

doi: 10.1295/polymj.11.353pmid: N/A

An investigation was carried out on the molecular microstructure of poly(trifluoroethylene) (PTRFE). With the high-resolution 19F-NMR spectrum of PTRFE and the computer simulation of the same polymerization system, the amount of backward-added monomer units and their distribution in polymer chain were estimated. The distribution is represented by the reactivity ratios of head- and tail-position of the unsymmetrical monomer to each propagating polymer radical. The assignment of absorption peaks of 19F-NMR spectrum of PTRFE was made on an empirical basis, and four possible structures, containing 5 carbon atoms along the polymer chain with a –CF2– group as the central group, were figured out. The percentage of backward-added trifluoroethylene (TRFE) in the PTRFE chain polymerized at 22°C was 50%. Denoting CFH-position CF2-position in TRFE (CFH=CF2) by B and A, respectively, the reactivity ratio of B and A of TRFE to the – – – CF2· radical was estimated as B/A=1/0.75 and that of TRFE to the – – – CF· radical was 1/1.33.

Rabie, A M; Aly, M I; Hegazy, S A; El-Awady, N I

doi: 10.1295/polymj.11.359pmid: N/A

4-Vinylpyridine was grafted on polyethylene films of different thicknesses by the direct irradiation method using a Co-60 γ-irradiation source. Addition of different amounts of solvents such as methyl ethyl ketone and cyclohexanone was found to decrease the swelling and the grafting extent on polyethylene. The dependence of the rate of graft polymerization on the thickness of the films was studied. The rate of grafting was found to decrease with increasing film thickness and a first order dependence was obtained. The effect of radiation dose on some of the mechanical properties of the ungrafted and grafted polyethylene was examined. It was found that low doses cause an increase in elongation due to a degradation process of polyethylene chains. At high doses, elongation tends to decrease again due to crosslinking, while the tensile load is not affected. Low grafting percents of 4-vinylpyridine on polyethylene lead to a marked decrease in elongation of the grafted polymer, with almost no change in the tensile load. Increasing the extent of grafting causes a significant increase in the tensile load and almost the same decrease in elongation as for the low grafted polymer.

Yokoyama, Yasuaki; Okada, Masahiko; Sumitomo, Hiroshi

doi: 10.1295/polymj.11.365pmid: N/A

The cationic polymerization of 1,3-dioxolane (DOL) initiated with methyl fluorosulfonate was investigated in deuteriochloroform (CDCl3) or nitromethane-d 3 (CD3NO2) at five different temperatures ranging from −20 to 5°C by means of 1H- and 13C-NMR spectroscopy. Only an ester growing species was observed in CDCl3 solution throughout the polymerization, while the simultaneous presence of ester and ionic species was confirmed in CD3NO2 solution, except in the final stage of the polymerization where the ionic species was barely detectable. Kinetic analysis of the polymerization in CDCl3 gave the rate constant of propagation, which varied from 0.7×10−2 (−20°C) to 2.3×102 l/mol· s (5°C). The activation enthalpy ΔH p ‡ and the activation entropy ΔS p ‡ for the polymerization in CDCl3 were evaluated from the temperature dependence of the k p values: ΔH p ‡=6.1±0.4 kcl/mol and ΔS p ‡=−42±1 al/mol· deg. On the basis of these results, the mechanism of the polymerization of DOL by superacid derivatives is discussed in comparison with that for tetrahydrofuran.

Ikeno, Shinobu; Yokoyama, Masaaki; Mikawa, Hiroshi

doi: 10.1295/polymj.11.371pmid: N/A

Highly conductive N-methylquinolinium– and quinolinium–TCNQ (tetracyanoquinodimethane) complex salts were blended with insulating polymers such as polystyrene or polysulfone to obtain polymers with high dielectric constants even in high frequency regions. Owing to the high conductivity of the conductive phase, blend polymers containing 2.2–4.6 wt% of TCNQ salts exhibit high dielectric constants (εr, 20–100) up to 1 MHz at room temperature. The relaxation frequencies of these blend polymers are thus higher, by ca. two orders of magnitude, than those of blend polymers with N-n-butylquinolinium–TCNQ complex salt with conductivities about 10−3 of the present TCNQ salts. The application of ca. 30 kV/cm of DC voltage to some of the virgin samples especially alters the resistivities of blend polymers having resistivities below 1011 Ω cm; resistivities tend to increase for those polymers having lower TCNQ salt concentrations, and to decrease for polymers with higher TCNQ salt concentrations. This application of high DC voltage renders the blend polymers excellent dielectrics whose εr and tanδ are 20–100 and 10−2–10−3 at low frequencies.

Kodaira, Toshiyuki; Yamazaki, Kazuyuki; Kitoh, Tadahiro

doi: 10.1295/polymj.11.377pmid: N/A

Polymerization behaviors of several 1,7-dienes were investigated in order to see the correlation between their cyclopolymerizability and the polymerizability of their monofunctional counterparts. In connection with this problem, studies on the effect of the intermolecular hydrogen bonds between monomers or between a monomer and a solvent on the cyclopolymerizability of these dienes have also been undertaken. sym-Dimethacryloyldimethylhydrazine, whose monofunctional counterpart does not polymerize, showed high cyclopolymerizability irrespective of the solvents used. sym-Dimethacryloylhydrazine and sym-diacryloyldimethylhydrazine, whose monofunctional counterparts polymerize, showed low cyclopolymerizability, though their ability to form hydrogen bonds is extremely different. The results thus obtained support the idea that the high and low cyclopolymerizabilities of these monomers are mainly associated with the low and high polymerizabilities of their monofunctional counterparts, respectively, but not with the ability to form hydrogen bonds, in agreement with the theory proposed previously.

Asano, Tsutomu; Fujiwara, Yasuna; Yoshida, Toshiho

doi: 10.1295/polymj.11.383pmid: N/A

Isotactic polypropylene was crystallized under temperature gradient and an oriented β-phase sample was obtained. The β-phase film was rolled in three orthogonal directions at 68, 96, 122, and 142°C. The deformation behavior was investigated by wide angle and small angle X-ray diffraction methods. Anisotropy in deformation was observed in each case, including the rotation of lamellae, interlamellar slip, longitudinal and transversal chain slip. At high temperatures, the deformation proceeded mainly by interlamellar slip whereas chain slip could hardly be observed. During the hot roll deformation, the original β-phase crystal was destroyed and then recrystallized into the c-axis-oriented α-phase crystal. The amount of the β→α phase transition increased with increasing rolling temperature and draw-ratio. The spacing of the newly appeared α-phase lamellae changed, depending only on the rolling temperature. The final c-axis-oriented texture was composed of α-phase crystals. From these results, it is considered that the deformation proceeds, not by incorporation of the original lamellar blocks, but through the melting or unfolding of the original β-phase lamellae and subsequent recrystallization into the c-axis-oriented α-phase lamellae.

Somorin, Oyin; Nishi, Norio; Tokura, Seiichi; Noguchi, Junzo

doi: 10.1295/polymj.11.391pmid: N/A

Chitin was converted into benzyl and also benzoylchitins. Benzylchitins up to 0.8 benzylated were prepared by the reaction of alkali chitin with benzyl chloride in dimethyl sulfoxide. The solubility of benzylchitins in organic solvents was not so good, because of the low degree of benzylation. Variously benzoylated chitins up to 1.8 mol benzoylated per residue were prepared by the benzoylation of chitin in a benzoyl chloride–methanesulfonic acid mixture at 0°C. Benzoylchitins were soluble in many organic solvents, e.g., dimethyl sulfoxide, dimethylformamide and benzyl alcohol, in addition to the acidic solvents such as formic acid. Infrared absorption spectra for benzyl and benzoylchitins were also investigated.

Hiraoki, Toshifumi; Kaneko, Motozo; Hikichi, Kunio

doi: 10.1295/polymj.11.397pmid: N/A

13C- and water proton-nuclear magnetic relaxation times were measured as functions of temperature and pH to study the interaction of Cu(II) with poly(D-glutamic acid) (PGA) in aqueous solution. In the pH region from 4.5 to 8, the addition of Cu(II) significantly influences the relaxation times of Cγ and Cδ carbons, while those of Cβ, Cα, and peptide C′ are not influenced. The relaxation times of Cγ and Cδ increase with increasing temperature, indicating that a fast exchange between the complexed and uncomplexed states occurs. The scalar relaxation is dominant to line broadening, suggesting that a significant amount of electron spin density is transferred from Cu(II) to Cγ Above pH 9, no paramagnetic effects of Cu(II) upon 13C spectra of PGA were observed. The water proton relaxation of Cu(II) aqueous solution is markedly enhanced by the addition of PGA at an acidic pH, but suppressed at an alkaline pH. These results show that carboxylate groups of PGA and water molecules are bound to Cu(II) at pH≤8, but excluded from Cu(II) at pH≥9.

Kobayashi, Shiro; Morikawa, Kenji; Saegusa, Takeo

doi: 10.1295/polymj.11.405pmid: N/A

Cyclodimerization of ethylene oxide (EO) to 1,4-dioxane (DON) by using superacids and their derivatives as catalysts was examined. Results are discussed on the basis of the catalyst nature. Kinetic analyses were performed by monitoring the reaction with 1H- and 19F-NMR spectroscopy. The rate constant of initiation (ki) and the apparent one of propagation (k p(ap)) were obtained. The rate constant of propagation due to ester species (k p(e)) was evaluated from a model reaction. The EO consumption rate could not be explained by assuming only ester active species. It was found that in addition to the ester species oxonium active species was responsible for the EO consumption, even if they were not detected by 19F-NMR. A general scheme is presented and discussed. A model reaction of a “back-biting” process was also studied.