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Volume 46, Issue 10
Displaying 1-12 of 12 articles from this issue
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A Simple Method for Crosslinking Density DeterminationAkira TAKAHASHI, Junko TANAKA, Tadaya KATO1989 Volume 46 Issue 10 Pages 571-575
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSWater-adsorbing poyelectrolyte gels having various crosslinking densities and also with different degrees of neutralization were prepared by copolymerization of acrylic acid monomer with methylenebisacrylamide as crosslinking agent. Determinations of their crosslinking densities, that is, the structure factors of the gels, were carried out by a rubber elasticity measurement. Elastic moduli were measured as follows: A small glass bead with appropriate weight was placed on the surface of the packed gel in a small vessel and the depth of gel deformation due to the bead weight was observed by a traveling microscope. This is called the Hertz method. The values of gel structure factor measured by elasticity appeared to be about two orders of magnitude smaller than the values calculated from the amount of crosslinking agent. Then, the network structures of such gels were thought to be incomplete. Moreover, the structure factors estimated on the basis of the Flory theory of gel swelling had the same order of magnitude as, but were slightly larger than the values from elasticity, if the effective degree of counterion dissociation in gels were assumed as small as in polyelectrolyte solution.View full abstractDownload PDF (868K) -
Hirofumi YAJIMA, Toshiyuki MIYAMOTO, Ryuichi ENDO, Setsuko FURUYA1989 Volume 46 Issue 10 Pages 577-581
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSCo (II) -alginate complex film (ACF) prepared by soaking sodium alginate (AN) film in the solution of Co (II) salt is hydrochromic. In order to gain better information on the susceptibility of ACF to moisture and to explore the practicability of ACF for use as a humidity sensor, the effects of relative humidity (RH), thickness (D) of the film, and molecular weight (Mv) of AN on the hydrochromism of ACF were studied in the processes of adsorption and release of water. The ACF exhibited a blue shift of the maximum absorption band from 560 nm to 520 nm, accompanied by some hypochromism in the transient process, with the increase in the moisture content of the ACF. The respondency of hydrochromism of the ACF was increased with increasing the degree of the change in RH and with decreasing the D and Mv values. On the other hand, the study of the removal process of moisture from the ACF showed that the water molecules coordinated to Co2+ in the ACF were very difficult to release. The above results suggest that thin filmization and a considerable elevation of the rate of release of the coordinated water molecules are required to achieve enough practicability of ACF for use as a humidity sensor.View full abstractDownload PDF (724K) -
Akira MATSUMOTO, Hiroyuki ANDO, Masayoshi OIWA1989 Volume 46 Issue 10 Pages 583-589
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSMethyl methacrylate was radically copolymerized with trimethylolpropane trimethacrylate (TMPMA) using dioxane or n-butyl acetate as a good or poor solvent, respectively, and the solvent effect on the gelation is explored in detail. The delay between the actual gel point and the theoretical one was usually larger in dioxane, suggesting a significance of the excluded volume effect on the intermolecular crosslinking reaction. On the other hand, the delay of the actual gel point from the theoretical one was larger in n-butyl acetate for the copolymerization in high dilution with a small amount of TMPMA; this may be ascribed to a quite reduced amount of pendant vinyl groups, responsible for crosslinking, in the prepolymer as a reflection of the enhanced occurrence of intramolecular crosslinking. The loop structure through intramolecular cyclization in the primary chain was formed to a larger extent in n-butyl acetate.View full abstractDownload PDF (1294K) -
Kazuhiko ISHIHARA, Tomoko UEDA, Nobuo NAKABAYASHI1989 Volume 46 Issue 10 Pages 591-595
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESS2-Methacryloyloxyethyl phosphorylchorine (MPC) and n-butyl methacrylate (BMA) were copolymerized to make a hydrogel membrane having phospholipid polar groups. The release behavior of 1, 4-di (2-hydroxyethoxy) benzene (DHEB) as a model drug from the membrane was investigated. The release rate of DHEB from the membrane increased for higher MPC compositions in the copolymer. The values of the diffusion coefficient of DHEB were in the range 1.7×10-7-1.9×10-6cm2/s. The release rate could be reversibly regulated in response to the temperature change. The phenomena corresponded to the change in the swelling degree of poly (MPC-co-BMA) membrane in water. The adsorption amount of plasma proteins, such as albumin and γ-globulin on the surface of poly (MPC-co-BMA) was quite small compared with poly (2-hydroxyethyl methacrylate) [poly (HEMA) ], which is known as a typical hydrogel and hydrophobic poly (BMA). The release rate of DHEB from poly (HEMA) membrane in the presence of these proteins dropped to about 70% of that in the absence of proteins. However, in the case of poly (MPC-co-BMA) membrane, the release rate stayed at the 85-90% level. This result is based on the suppresion of protein adsorption by MPC moieties in the membrane.View full abstractDownload PDF (948K) -
Hirohisa YOSHIDA, Tatsuko HATAKEYAMA, Kunio NAKAMURA, Hyoe HATAKEYAMA1989 Volume 46 Issue 10 Pages 597-602
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSThe glass transition of hyaluronic acid hydrogel samples with various water contents ranging from 0 to 0.5 (grams of water per gram of dry hyaluronic acid) was investigated by differential scanning calorimetry (DSC). Water in hydrogel was classified into three types: non-freezing, freezing bound, and free water. For Wc values less than 2.0, hydrogel formed the glassy state by cooling from room temperature to 150 K at 10 Kimin. The difference in the heat capacity (ΔCp) between the glassy state and the liquid state at Tg was measured. The Tg of the system with Wc values higher than 0.5 agreed well with the calculated Tg assuming the following equation: Tg= (φ1ΔCp1Tg1+φ2ΔCp2Tg2) / (φ1ΔCp1+φ2ΔCp2), where Tg1=185.7K, ΔCp1=0.321 J/kg, which are experimentally obtained from the water-hyaluronic acid system with Wc=0.5; Tg2=135K, ΔCp2=1.94J/kg which are obtained from amorphous ice. The weight fraction (φ2) of the glassy water was estimated from the heat of cold crystallization according to the following equation φ2=w2/ (w1+w2), φ1+φ2=1, where φ1, w1 and w2 are weight fraction of hyaluronic acid, amount of hyaluronic acid and of glassy water, respectively. The ΔCp of glass water (ΔCp2) was estimated by asumming ΔCp=ΔCp1+ΔCp2w2 where Δ Cp is the observed value. The obtained ΔCp2 value extrapolated to the high Wc range corresponded well with the value of amorphous ice. This result suggests that the state of the glassy water in the system is similar to that of the amorphous ice.View full abstractDownload PDF (1043K) -
Makoto SUZUKI1989 Volume 46 Issue 10 Pages 603-611
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSTo promote the developement of artificial muscles, we have investigated the feasibility and the improvement of ability of amphoteric poly (vinyl alcohol) (PVA) hydrogels. The influences of preparation conditions on the passive mechanical properties including anisotropy, dynamic contraction properties including response time, contraction ratio, generated power density etc. have been examined and are summarized. According to the results we have been able to produce a material with a generated power density about 0.1W/cm3 close to that of a skeletal muscle! The durability was also found to be very promising. The observation by means of cryo-SEM could assure still more improvement.View full abstractDownload PDF (2161K) -
Toshihiro HIRAI, Kohji HANAOKA, Takashi SUZUKI, Sadao HAYASHI1989 Volume 46 Issue 10 Pages 613-617
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSA membrane of poly (vinyl alcohol) (PVA) hydrogel which has high elasticity and shows anisotropic contraction was prepared by repetitive freezing-and-thawing under elongation from 10% (w/w) aqueous solution of PVA. The oriented hydrogel membrane, thus prepared, contracted instantly in aqueous saline solution, as the isotropic gel does. This gel also exhibited anisotropic contraction behavior, that is, the contraction in elongation direction was smaller than that in perpendicular one In both directions, the degree of contraction showed a maximum value at the elongation of 200%; further increase of the elongation caused a simple decrease of the contraction, while the anisotropy of contraction simply increased with the elongation. Polarizing microscopic analysis showed that the elongation of about 200% could only induce a slight orientation in gel network. X-Ray diffraction pattern of the gel membrane showed that the elongation of 200% could mainly cause a decrease of periodicity of the gel structure, instead of the increase of the crystallinity. It was concluded that the anisotropic contraction of the oriented gel membrane originated from the rigidity in elongation direction induced by the orientation of polymer network and the breakdown of the network in the perpendicular direction.View full abstractDownload PDF (1129K) -
Kazuo ARAKI, Jun TANAKA, Yoshio IMAMURA1989 Volume 46 Issue 10 Pages 619-624
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSThermoreversible atactic polystyrene gels (aPS) in carbon disulfide were formed in the temperature range from 20 to-90°C. ESR spectra were measured as a function of temperature, polymer concentration and molecular weight by spin probe and spin-labelled methods. The straight lines obtained from Arrhenius plots change their slopes at gelation temperature TEgel in the polymer concentration range from 70 to 140 g/l. Apparent activation energies ΔEsol obtained from this slope were 15.45±1.90 kJ/mol for sol state. Values of ΔEgel for gel state were smaller than ΔEsol, and increased with an increase of polymer concentration. For the concentrated polymer solutions, no change of the slope in Arrhenius plots was observed. The free volume fraction fgel (0.21) was independent of polymer concentration and molecular weight at Tgel. The behavior of the sol-gel transition was found to be strongly dependent on the free volume of polymer.View full abstractDownload PDF (952K) -
Kunihiko TAKEDA, Takafumi YAMAMIZU1989 Volume 46 Issue 10 Pages 625-633
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSBeads of porous crosslinked polystyrenes were prepared in the presence of pore formers by suspension polymerization. Macropores (here named “fixed pores”), formed in polymerization, were found to be greatly changed by different treatments after polymerization. Although porous polymers dipped in good solvents were found to lose their fixed pores, their pore structure was retained and fixed pores could be recovered. When dry, shrunken polymers were swollen in a good solvent, swelling time and the swelling ratio were found to be controlled by the amounts of their fixed pore volume. But the pore volume of swollen polymers were found to depend on the volume of pore formers in polymerization. These phenomena occurred because of the retention of the pore structure of polymers.View full abstractDownload PDF (1492K) -
Shuji SAKOHARA, Toshiyuki SAKATA, Masashi ASAEDA1989 Volume 46 Issue 10 Pages 635-638
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSAcrylamide-acrylic acid copolymer gel, a typical hydrophilic gel, was used as a membrane material for separation of organic solvent/water mixtures. The gel membrane was prepared by the radical copolymerization of monomers in the pores of silica-alumina thin membranes whose preparation techniques have been established in our laboratory, because the mechanical strength of the gel is too small to prepare a thin membrane. The separation of water/acetone mixture was performed by the pervaporation method. By controlling closslinking density under high gelation temperature, about 90°C, the extremely high selectivity was attained. This suggests that the gel membrane having the extermely high selectivity for separation of such mixtures can be prepared by controlling the structure and size of gel network.View full abstractDownload PDF (629K) -
Takao OHMORI, Mitsutaka KAWAMURA1989 Volume 46 Issue 10 Pages 639-641
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSThe collective diffusion coefficients, Dc, in polyacrylamide gels having the same network structure were measured as a function of volume fraction of polymer in gel with a dynamic light scattering method. In order to prepare the gels with different volume fractions of polymer, the gel samples were first produced under the same conditions and then swelled or shrunk by immersing in methanol or acetone-water solutions. The value of Dc decreased with the increase of the concentration of methanol (acetone) in the solvent; however, it then approached a constant value at a concentration near where the viscosity of the solvent is a maximum.View full abstractDownload PDF (559K) -
Eiji KATO, Mitsutaka KAWAMURA1989 Volume 46 Issue 10 Pages 643-645
Published: October 25, 1989
Released on J-STAGE: March 15, 2010
JOURNAL FREE ACCESSThe temperature dependence of the intensity of light scattered by the density fluctuations of polystyrene network (cross-linked by 0.1% divinylbenzene) swollen by cyclohexane was measured in a metastable state. The slope of the inverse intensity of the scattered light vs. the inverse absolute temperature curve was determined. The spinodal temperature at which the intensity of the scattered light diverges was determined as a function of the volume fraction of the network φ. In contrast to the prediction of the theory, the slope of the curve depends on φ and greatly increases with increase of φ. Unrealistic values for interaction parameters ΔH and ΔS, and for the number of chains are needed to make the obtained spinodal line coincide with that calculated from the theory.View full abstractDownload PDF (421K)
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