Polymer Journal

Sato, Kenji; Ouchi, Shuichi

doi: 10.1295/polymj.10.1pmid: N/A

Early stage hydroxymethylation of melamine with formaldehyde to form monomethylolmelamine in the weakly acidic region of 0<S<1.0, and in the absence of the catalyst, S=0 (pH, ca. 3—8) was investigated kinetically at 40°C in aqueous media; here S denotes [hydrochloric acid]0/[melamine]0. As a result, the hydroxymethylation rate in the region of O≤S<1.0 was found to be dependent on the concentration of the melamine molecule (base species) MH and its conjugate acid MH2 + in the following manner: rate=k H2O[MH][HCHO]+k H+[MH2 +][HCHO]+k MH2+[MH2 +] [MH][HCHO]+k MH[MH]2[HCHO]. In particular, the rate at S=0 was represented by rate=k H2O[MH][HCHO]+k MH[MH]2[HCHO]. The values of the rate constants (k H2O, k H+, k MH2+, and k MH) were obtained, and then the relative contributions of these four reactions at pH 3—8 were made clear in connection with the initial concentration of melamine.

Furue, Masaoki; Nakajima, Kaoru; Saeki, Masao; Nozakura, Shun-ichi

doi: 10.1295/polymj.10.13pmid: N/A

The formation of charge-transfer complexes of poly(N-methyl-3-vinylcarbazole (P3VCA) with tetracyanoethylene (TCNE), 2,4,5,7-tetranitro-9-fluorenone (TeNF), chloranil (p-CA), and 1,3,5-trinitrobenzene (TNB) was investigated spectrophotometrically. The association constants (K) of P3VCA complexes were 2.5 to 7.1 times larger than those of the corresponding monomeric analog, N-methyl-3-ethyl-carbazole. To clarify the polymer effect, copolymers of N-methyl-3-vinylcarbazole with styrene and with the dimer model, 1,3-bis[3-(N-methylcarbazolyl)]propane, were studied to obtain the details of the complex formation. The complex of the dimer model was found to be less stable than those of the monomer analog and P3VCA. It is suggested that large stabilities in the polymer system do not simply result from the local concentration effect, but also from the favorable arrangements of the neighboring carbazole units.

Yokota, Kazuaki; Kakuchi, Toyoji; Takada, Yoshiyuki

doi: 10.1295/polymj.10.19pmid: N/A

The cyclocopolymerizations of o-allylphenyl acrylate (APA) and 2-(o-allylphenoxy)ethyl acrylate (2-AOEA) with a donor monomer, p-chlorostyrene (p-ClS), in the presence of AlEti1.5Cl1.5 have shown that the electron-withdrawing double bonds are consumed in an equal proportion to the electron-releasing double bonds, irrespective of the initial composition of monomer feed. The copolymer composition tended to a limiting value with 50-mol % p-ClS units as the p-CIS mole fraction in the monomer feed increased. The extent of cyclization for the APA and the 2-AOEA units sharply decreased with an increase in the p-ClS unit fraction. The fraction of acrylic double bonds in the consumed double bonds always amounted to about 50-mol % this indicates that the cyclocopolymerizations are composed by alternating participation of the electron-withdrawing and the electron-releasing double bonds. On the other hand, the following values of kp/k c, the ratio of the rate constants for linear propagation and for cyclization, were obtained for APA at 40°C: 0.20 l mol−1 in the presence of AlEti1.5Cl1.5 and 0.045 l mol−1 in the presence of AlEtCl2. These values imply that the intramolecular interaction between the two double bonds plays an important role in the cyclopolymerization. The results have indicated that the mechanism being proposed for the alternating copolymerization would be applicable also to the cyclocopolymerization. The character of cyclocopolymerization was explained by the molecular complex mechanism rather than by the complexed radical mechanism.

Miyakawa, Harumitsu; Saitô, Nobuhiko

doi: 10.1295/polymj.10.27pmid: N/A

The effect of intramolecular interactions on the configration of a flexible polymer molecule is investigated by the method of cluster expansion. Using the first approximation which takes account of the special type of diagrams, expansion parameters for the mean square end-to-end distance and the mean square radius of gyration are calculated near the Θ-temperature. It is shown that both expansion parameters are singular at the Θ-temperature. The expansion parameter for the mean square radius of gyration is a measurable quantity and to find the singularity experimentally it is necessary to measure the mean square radius of gyration at the temperature |T−Θ|<1K for N=500 or |T−Θ|<3K for N=100.

Hara, Masanori; Nakajima, Akio

doi: 10.1295/polymj.10.37pmid: N/A

The formation of a polyelectrolyte complex between heparin (Hep) and aminoacetalized poly(vinyl alcohol) (PVAA) in aqueous media has been studied by measurements of turbidity, metachromasy, and induced circular dichroism. Three results were noted: (a) the Hep—PVAA complex in aqueous system is either in a state of liquid-solid equilibrium, or a homogeneous solution, according to the mixing conditions; (b) the reaction between Hep and PVAA was not perfectly stoichiometric; (c) the ordered structure of Hep was disordered by the formation of complex at low pH.

Mori, Tetsuo; Imada, Kazuhiro; Tanaka, Ryuichi; Tanaka, Takehide

doi: 10.1295/polymj.10.45pmid: N/A

The dynamic mechanical properties and the phase structures of some heterogeneous network polymers, such as poly(glutamic acid) [PGA]—poly(oxypropylene) glycol [PPG, Mn=400], PGA—poly(oxyethylene) glycol [PEG, Mn=330], and poly-(acrylic acid) [PAA]—PEG were compared to each other to investigate the relationship between the mechanical properties and the aggregation state of the component polymers. When compared with PGA—PEG300 at the same PGA content, the PGA—PPG400 showed the following characteristics: (1) the dynamic mechanical tanδ curves are much broader, (2) the tanδ peak temperatures are higher, and (3) the E′ values above the transition regions are lower. The most striking characteristics of PAA—PEG compared with PGA—PPG400 and PGA—PEG300 were: (1) E′ in the rubbery plateau region increases in proportion to the crosslink density; (2) the tanδ maximum values are as large as 1.0—1.5; and (3) the shape of the tanδ curves is sharp and is little affected by the composition. The differences in the properties among the heterogeneous network polymers were discussed in terms of characteristic properties of PGA, the compatibility of the component polymers, and the reaction temperature.

Hayashi, Shizuo

doi: 10.1295/polymj.10.59pmid: N/A

Two kinds of relaxation processes are introduced for the theory of nonlinear viscoelasticity of temporarily crosslinked network structure. One is the chain-slip and the other is the change in number of chains as a function of time. Three assumptions are made for this theory: (1) The relaxation process for the chain-slip is a linear process characterized by a single relaxation time; (2) The chain breakage coefficient is proportional to the absolute value of the average force acting on a chain; (3) The rate of chain creation is constant. The following results are obtained for typical deformations. (1) The viscosity in the steady flow with a constant shear rate is non-Newtonian and at high shear rates its molecular weight dependence deviates from the 3, 4-th power law of viscosity. (2) The stress growth at the onset of the shear flow with a constant shear rate shows a stress overshoot which is prominent at a high shear rate. (3) The stress relaxation at a constant deformation shows a non-linear strain dependence corresponding to relatively short periods of time and a linear relaxation tendency for relatively long periods of time. (4) The stress relaxation at a sudden termination of the shear flow shows a strain rate dependence initially and a linear tendency for long periods of time. A new type of constitutive equation in which the memory function is one of the invariants of the internal strain determined by the slip equation was found by investing the relation between the present theory and the phenomenological constitutive equation.

Kamachi, Mikiharu; Kohno, Masahiro; Liaw, Der Jang; Katsuki, Shuhei

doi: 10.1295/polymj.10.69pmid: N/A

An ESR study on the radical polymerization of methyl methacrylate and its homologs was carried out in frozen aromatic solvents, using benzoyl peroxide as a photosensitizer. A well-resolved 9-line spectrum was observed and its intensity distribution was found to change with temperature and the medium. In order to elucidate the origin of the 9 lines, deuterated methyl methacrylates and triphenylmethyl methacrylate having a bulky ester group were used. A 4-line spectrum (1:3:3:1) was observed for methyl methacrylate-β-d 2 (MMA-β-d 2). A 3-line spectrum, whose intensity distribution was not binomial, was recorded for methyl-d 3 methacrylate (MMA-d 3). A 5-line spectrum (1:4:6:4:1) was recorded for triphenylmethyl methacrylate. The temperature dependence of these spectra was also investigated. It was concluded from these results that the two conformations of the propagating radicals are responsible for the 9-line spectrum of methyl methacrylate in glassy aromatic solvents.

Yassin, Ahmady A; Rizk, Nadia A

doi: 10.1295/polymj.10.77pmid: N/A

The elucidation of the mechanism of inhibition and retardation of polymerization reactions of quinones has been investigated using the charge-transfer complexes of N,N-dimethylaniline (DMA) and triphenylphosphine (TPP) with chloranil as inhibitors for the bulk and solution polymerizations of vinyl acetate (VA) in benzene and in acetonitrile. The complexes have proved to be very efficient inhibitors. The efficiency of inhibition was found to depend on the stability of the complexes, the nature of the electron donor, and its ratio relative to chloranil, as well as on the polarity of the solvent. The greater efficiency (1) in the polar solvent and (2) of the complexes of TPP compared with that of the amine support the idea that inhibition reactions involve electron transfer from the growing radicals to the quinone, with the formation of molecular complexes of macrocations and semiquinone anions. The latter are the actual inhibiting species, so that the inhibiting efficiency is determined by the feasibility of their formation in the polymerizing system. The nature of the inhibition products depends on the extent to which the semiquinones are found as kinetically independent species in the medium. The inhibition reactions should accordingly be considered as oxidation—reduction processes in which the growing chains are the electron donors.

Ishiwari, Kazuo; Hayashi, Toshio; Nakajima, Akio

doi: 10.1295/polymj.10.87pmid: N/A

Monomer reactivity ratios in the N-carboxyanhydride (NCA) copolymerization of γ-benzyl L-glutamate with L-valine initiated by triethylamine (TEA) in a 1:1-(v/v) mixture of dioxane and dichloromethane at 25°C were determined. The methods used were a differential linearization graphical method, and a nonlinear least-square method which takes into consideration the change of monomer concentration with increasing conversion. Since the reactivity ratios are very sensitive to copolymer composition, four analytical methods have been employed to determine the copolymer composition, i.e., the amino acid analysis, elemental analysis, and ultraviolet and infrared spectroscopies. The numerical values of the monomer reactivity ratios obtained were r 1(γ-benzyl L-glutamate)=2.96 and r 2(L-valine)=0.17.