Yoshiaki Motozato

Molecular motions and segmental size of vulcanized natural and acrylonitrile-butadiene rubbers by the spin-probe method

Abstract Nitroxide radicals were dispersed as paramagnetic probes in natural and acrylonitrile-butadiene rubbers, differing in the content of combined sulphur, and their molecular motions were investigated through the motion of the probe inspecting e.s.r. spectra. Broad e.s.r. spectra at low temperatures changed into sharp ones around or above T g of the rubbers, showing the rapid narrowing of the extreme line separation of triplet spectra. From the activation energy of the rotational motion of the probe, calculated from the temperature dependence of the rotational correlation frequency, it was deduced that the self-diffusion of the probe through polymer matrices and polymer segments had occurred around or above T g . The temperature narrowing of the line separation was correlated to the glass transition of the rubbers and a relation between the temperature narrowing, T g and the molar volume ratio of the segment to the probe on the basis of the hole theory, was proposed. From this theory, the size of segments of the rubbers was estimated.

Preparation and properties of cellulose spherical particles and their ion exchangers

Preparation a partir de solutions de triacetate de cellulose en presence de differents diluants qui permettent de controler la dimension des pores des particules spheriques

Studies on the surface of as-grown and annealed polyethylene single crystals by the spin-probe method

Abstract Studies on molecular motions at the surface of as-grown and annealed polyethylene single crystals in relation to the surface structure have been made by dispersing electron paramagnetic probes on the surface of the crystals and detecting them by the electron spin resonance method. A relatively large scale molecular motion supposedly associated with the glass transition was detected as a change in hyperfine patterns at around −50°C. Rotational correlation frequency of the paramagnetic probe was found to rapidly increase above the crystallization temperature suggesting that the new mode of molecular motion takes place by thickening of crystals. For the annealed crystals the frequency was much depressed compared with that of the as-grown crystals indicating the decrease in mobility of the surface by annealing. Extensive study revealed that the mobility of the surface of annealed crystals is uniquely determined by the increased portion of the lamellar thickness by annealing.

Macroporous glucomannan spheres for the size-exclusion separation of aqueous macromolecules

Abstract New spherical gels for the high-speed size-exclusion separation of aqueous macromolecules were developed. The gels were prepared by the “sphering” of glucomannan triacetate (from a Amorphophalus konjac) by means of a suspension and evaporation method, followed by a saponification and cross-linking with epichlorohydrin. By adjusting the preparation conditions, spherical gels were obtained with varying exclusion characteristics. For example, polyoxyethylene with a molecular weight below 10 3 and above 10 7 in the absence or in the presence of a diluent during the sphering process, respectively. In addition, the packing exhibited a high sample capacity and good pressure stability. These favourable properties are attributable to the low degree of swelling of the glucomannan spheres. The gel permeation chromatography of phosphate bilayer membranes (aggregate weight ca. 10 7 ) was investigate.

NOVEL PACKING FOR HIGH PRESSURE LIQUID CHROMATOGRAPHY. PARTIALLY ALKYLATED AND CROSS-LINKED PMLG SPHERICAL PARTICLES.

Abstract Novel spherical and macroporous particles for the high pressure liquid chromatography were prepared by our unique method. The packing was composed of poly-γ-methyl-L-glutamate, and were functionalyzed by the partial cross-linking and long-chain alkylation. The packings are very rigid and show satisfactorily chromatographic properties. They are attributable to the suitable polarity and hydrophobicity introduced by polypeptide-units and long-chain alkyl groups, respectively.

Viscosity of aqueous glucomannan-borate complex solutions

Abstract The viscosity of aqueous konjac glucomannan solution in the presence of borate ions was examined. The measurements were made on a rotational viscometer. The apparent viscosity of each sample was determined over the glucomannan concentration range of 0.09–0.45% w/v. In the concentration region above the critical concentration, 0.29% w/v, the viscosity was increased considerably by the presence of borate ions. This may be due to the creation of new interchain crosslinks, involving the formation of a 2:1 anionic complex (dicomplex). On the other hand, in the more dilute region the viscosity was almost independent of the presence of borate ions. In this region the formation of a 1:1 anionic complex (monocomplex) takes place predominantly and does not contribute effectively to the increase in viscosity.

Study of relationship between network structure of g.p.c. gels and molecular size of permeable substance

Abstract Attempts were made to correlate the average size of the network of crosslinked vinyl acetate-glycidyl methacrylate (GMA) copolymer to the maximum size of permeable molecules when the copolymers were used as g.p.c. packing materials. The root-mean-square of the end-to-end distance ( r 2 ) 1 2 of the hydrodynamic radius ( s 2 ) 1 2 , which characterizes the maximum extent of the molecules, were calculated. Meanwhile, the average size of the copolymer network, rc, was estimated from the average molar weight between crosslinkages, this being calculated from the equilibrium rubber elastic modulus, Er, obtained by dynamic discoelastic measurements. It was found that the maximum size which can permeate the copolymer decreases as the content of GMA in the copolymer increases. From viscoelastic measurements, Er was found to increase as the content of GMA in the copolymer increases. Further, linear relationships were obtained among rc, ( r 2 ) 1 2 , and ( s 2 ) 1 2 covering the wide range of the copolymer composition.

Gel permeation chromatographic properties of poly(vinyl alcohol) gel particles prepared by freezing and thawing

The gel permeation chromatographic properties of poly(vinyl alcohol) gel particles prepared by a freezing-and-thawing procedure were investigated. From the calibration graph established with poly(ethylene glycol) and poly(ethylene oxide) samples, it was found that the value of the excluded molecular mass increased from 2500 (original) to 6000 (fifteen repeated cycles of freezing and thawing). In addition, the treated gels showed a favourable pressure-resisting property.

Studies on Inclusion Behaviors of β-Cyclodextrin-Starch Composite Gel by Spin Probe Method

Abstract A composite gel prepared from β-cyclodextrin and starch in a 1:2 ratio and cross-linked by epichlorohydrin was used as a host compound for inclusions. The competitive inclusion between 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxy and chloro-substituted acetic acids was monitored by ESR spectroscopy. The triplet signals enabled us to estimate the rotational correlation frequencies of the radical by employing Kivelsons equation. The unusual temperature dependence of the frequencies suggests that gradual loosening of the gel link occurs with an increase of temperature from 30 to 60°c, resulting in increased amounts of the inclusion which cancels the increments of the correlation frequencies. The gel is found to be a better host than β-cyclodextrin for dichloro, monochloro, and un-substituted acetic acids, at least below 50°c. Trichloroacetic acid is included in the gel as much as is dichloroacetic acid, but much more than monochloroacetic acid and acetic acid, which still compete comparably with ...

Excluded chain dimensions and network size in g.p.c.

Abstract Attempts have been made to correlate the average network size of polystyrene, poly(methyl methacrylate), poly(methyl acrylate), poly(n-butyl acrylate) and poly(vinyl acetate) gels with the maximum size of the polymer molecule which can permeate the gels. The average size of the network structure ( r c ) was estimated from the average molecular weight between crosslinkages ( M c ) derived from the glass transition temperatures of the gels. The maximum molecular size which could permeate into the network was expressed as the root-mean-square end-to-end distance [ ( r 2 ) 1 2 ] of the permeable substance with the molecular weight at exclusion limit ( M lim ) obtained by gel permeation chromatography. Both r c and ( r 2 ) 1 2 decreased with increasing total dose of γ-irradiation or increasing amount of the crosslinking agent. Linear relations were also obtained between r c and ( r 2 ) 1 2 covering a wide range of total dose and amount of the crosslinking agent.