Polymer Journal

Shirahama, Hiroyuki; Suzawa, Toshiro

doi: 10.1295/polymj.16.795pmid: N/A

The surface characteristics of carboxylated polymer latices—styrene/acrylic acid copolymer (PS/PAA) and styrene/methacrylic acid copolymer (PS/PMAA)— were investigated. Polystyrene (PS) latex was used as a reference sample. These latices were prepared in a soap-free system, using potassium persulfate as the initiator. Conductometric titration curves of PS and carboxylated latices showed both strong and weak acid groups to exist on the surface of latex particles. The surface charge density (σ) for PS/PAA latex was proportional to the amount of acrylic acid (AA) used in the copolymerization (thus, σ- for PS/PAA5 latex was larger than that for PS/PAA2 latex; the subscripts 5 and 2 represent the mol% of AA monomers used in the copolymerization). However, σ for PS/PMAA5 latex was smaller than that for PS/PAA5 latex, although the mol% of acid monomers used in the copolymerization was the same for both latices. σ for carboxylated latices increased with increasing pH, but the pH dependence of σ for PS latex was not very pronounced. The ζ-pH curves for these latices were considerably different from the σ-pH curves. This is probably because the Stern potential and the position of the shear plane in the electrical double layer differ between the two latices. Methylene Blue adsorption onto PS and PS/PAA latices was measured as a function of pH. The overall tendency of the dye adsorption was more similar to the σ-pH curves than the ζ-pH curves.

Chen, Guan-Wen; Hayashi, Toshio; Nakajima, Akio

doi: 10.1295/polymj.16.805pmid: N/A

Membranes of A–B–A tri-block copolymers were prepared by polymerizing poly(γ-benzyl D,L-glutamate) or poly(γ-methyl D,L-glutamate) as the A component and polybutadiene as the B component. The mechanical properties of and the hydraulic permeability of water were examined and compared with those properties for A–B–A tri-block copolymers consisting of poly(γ-benzyl L-glutamate) or poly(γ-methyl L-glutamate) as the A component and polybutadiene as the B component. The temperature dependence of the dynamic modulus and the loss modulus were investigated based on Takayanagi’s mechanical model. The mechanical properties led to the conclusion that the dynamic mechanical spectra could be well explained by the microheterophase structure observed with an electron microscope. In the case the shape of the inclusion phase was assumed to be spherical, the storage modulus E′ calculated by means of Takayanagi’s equation showed excellent agreement with the experimental data for D,L-type block copolymers, indicating that spherical inclusion phases exist in them in spite of their rather high volume fractions of the B portion. The hydraulic permeability coefficient K of water through D,L-type block copolymer membranes was remarkably lower than that of L-type membranes. This may indicate that the A domains are homogeneous in shape and dispersion state for the D,L-type block copolymer, owing to the existence of a molecular chain portion capable of forming interchain hydrogen bonds.

Sumi, Akira; Okada, Masahiko; Sumitomo, Hiroshi

doi: 10.1295/polymj.16.815pmid: N/A

A new polysaccharide analogue (2) having regiospecifically a benzyloxy group and a cyano group in its repeating unit was synthesized by the cationic ring-opening polymerization of 4(a)-benzyloxy-3(e)-cyano-6,8-dioxabicyclo[3.2.1]octane (1). The bicyclic acetal 1 was prepared from 3,4-dihydro-2H-pyran-2-carbaldehyde (acrolein dimer) via six reaction steps. The ring-opening polymerization of 1 proceeded, though very slowly, in dichloromethane at temperatures between −60 and 0°C in the presence of strong Lewis acids such as antimony pentafluoride and antimony pentachloride as initiators, yielding polyacetals (poly(3(e)-benzyloxy-4(a)-cyanotetrahydropyran-6,2-diyloxymethylene)) with number average molecular weights of ∼1.4×104. 1H and 13C NMR analysis disclosed that polymer 2 consisted exclusively of tetrahydropyranoside units linked in a (1→6)-α fashion according to carbohydrate chemistry terminology. On heating the polymer 2 with potassium hydroxide in an aqueous 2-methoxyethanol solution, inversion of the configuration of the carbon atom bearing the cyano group occurred to give a structural unit having the cyano group in the equatorial position. The polymerization reactivity of 1 was markedly lower than those of analogous bicyclic acetals. The retarding effect of the cyano group on the polymerization of 1 is discussed.

Kamide, Kenji; Matsuda, Shigenobu

doi: 10.1295/polymj.16.825pmid: N/A

An attempt was made to determine the concentration dependence coefficients, p 1 and p 2, of the polymer-solvent interaction parameter χ[χ=χ0(1+p 1 v p+P 2 v p 2); χ0; concentration independent coefficient, v p; polymer–volume fraction] from the critical solution concentration v p c and the weight- and z-average relative molar volume ratios of the polymer to the solvent, Xw and Xz, of polymer samples in multicomponent polymer–single solvent systems and evaluate the Flory’s theta solution temperature θ and entropy parameter ψ for a system using the critical solution temperature T c and critical χ0 parameter χ0 c. For this purpose, a theory is proposed to calculate χ0 c from p 1, p 2, Xw, and Xz. The method was applied to the literature data of upper and lower critical solution point (UCSP and LCSP) regions for polystyrene (PS)–cyclohexane (CH) and PS–methylcyclohexane systems. The values of p 1 and p 2, thus obtained for UCSP of PS–CH system, were in good agreement with those estimated by Kamide et al. from the cloud point curve. The θ and ψ values obtained are compared with those by the Koningsveld et al. method using the same critical point data and with those by the second virial coefficient method.

Kamide, Kenji; Matsuda, Shigenobu; Dobashi, Toshiaki; Kaneko, Motozo

doi: 10.1295/polymj.16.839pmid: N/A

An attempt was made to establish a theoretical method for calculating the cloud point curve (CPC) and critical point of solutions of polydisperse polymers in a single solvent (i.e., quasi-binary system) on the basis of the polydispersity of the polymer and concentration- and molecular weight-dependences of the polymer–solvent thermodynamic interaction parameter χ. Expressions giving the cloud point curve were derived and a computer simulation technique, based on the theory, was developed. The effects of the average molecular weight, polydispersity of polymer and concentration dependence of χ-parameter on CPC, threshold cloud point and critical point were clarified. In order to represent accurately the CPC for the entire concentration range from the molecular characteristics of the original polymer and operating conditions, such as polymer–volume fraction and χ-parameter, the concentration dependence parameters p 1 and p 2, in the relation χ=χ0(1+p 1 v p+P 2νp 2) (χ0; concentration-independent parameter, v p, polymer volume fraction) should be adequately taken into account. Very delicate changes in p 1 and p 2 cause significant variation in CPC and none of the literature data on p 1 and p 2 for polystyrene/ cyclohexane adequately represent the experimental CPC. From an actual CPC experiment, p 1=0.643 and p 2=0.200 were evaluated. The effective role of the molecular weight dependence of χ in CPC was shown in the lower v p region.