Magnetic field effects on sol-gel phase changes in aqueous polymers

Yamamoto, Ichiro; Matsumoto, Yusuke; Yamaguchi, M.; Shimazu, Yoshihiro; Ishikawa, Fumihiro

doi:10.1016/s0921-4526(97)00948-4

Cited by 20 publications

(15 citation statements)

References 5 publications

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“…1 indicate the magnetic-field dependence of the melting temperature, T m , of 0.5 wt% agarose gel. The average temperature was T m Z80.8 8C for the reference gel [4][5][6][7]. On the other hand, the gel exposed to the 5 T magnetic field melted at T m Z81.8 8C.…”

Section: Melting Temperaturementioning

confidence: 99%

The anisotropic properties of magnetically ordered gel

Yamamoto

Saito

Makino

et al. 2006

Science and Technology of Advanced Materials

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The preparation of gels under strong magnetic fields causes the molecular ordering of the gels. The relationships between the magnetic ordering and various physical properties of agarose gel at various concentrations were investigated. It was found that the ordering of the gel molecules is related to the phase transition temperature. Our measurements of the electrophoretic velocity of DNA, the elasticity of the gel and its ratio of shrinkage in acetone-water systems indicate that agarose gel has anisotropic properties. The experimental results indicate the presence of an anisotropic network structure in the gel. q

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Section: Melting Temperaturementioning

confidence: 99%

The anisotropic properties of magnetically ordered gel

Yamamoto

Saito

Makino

et al. 2006

Science and Technology of Advanced Materials

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“…These structures have a potential to undergo magnetic alignment and some of them actually undergo magnetic alignment. [50][51][52][53][54][55][56] However, the mechanism of these transitions itself is insufficiently clarified in most cases at present time so that it is difficult to reach a unified view of magnetic alignment occurring during transitions.…”

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confidence: 99%

Study on the Effect of Magnetic Fields on Polymeric Materials and Its Application

Kimura

2003

Polym J

237

206

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ABSTRACT:This paper reviews our recent work on the use of magnetic fields to the polymer processing. Polymers considered in this paper are not peculiar ones synthesized specially for the purpose of magnetic processing, but they are very usual ones including poly(ethylene terephthalate), polypropylene, etc. In this paper, two main magnetic effects on polymers are considered, i.e., alignment and levitation. In the first part, the magnetic torque causing the alignment is described. Then, examples of alignment in polymeric systems are presented, starting from simple cases such as magnetic alignment of fibers in a suspension to more complicated cases such as magnetic alignment of crystalline polymers in which mesophase formations and memory effects are involved. In the second part, the magnetic force acting on diamagnetic materials and its application to separation and processing of polymeric materials is described.KEY WORDS Diamagnetism / Magnetic Alignment / Magnetic Levitation / Phase Transition / Crystalline Polymers / Polymer Processing / Fiber / Magnetic effects on diamagnetic materials have been known since the age of Faraday, but it is very recent that the attention has been paid to the use of these effects to the processing of diamagnetic materials including inorganic, organic, and polymeric materials. This trend is partially due to the development of superconducting technology 1 that enables us to use high magnetic fields (10 T or more) in the study of materials science at individual laboratory level. Cryogen free (liquid-helium free) superconducting magnets, mostly manufactured by Japanese companies, are now on the market, with various types including a large bore type (45 cm at 3.5 T), a rotate bore type, a split type, a low fringe field type, a high field type (15 T, 52 mm in diameter), etc. These magnets are used in academia as well as industries for the processing purposes.High magnetic fields provided by these superconducting magnets have made it possible to visualize the magnetic effects on "non-magnetic" materials such as diamagnetic materials. Because the diamagnetism is very small compared to the ferromagnetism, we hardly experience in daily life the effects of magnetic field on plastics, water, and living bodies, etc. Some means must be devised to visualize these effects. A straightforward way is to use high magnetic fields. If we use a superconducting magnet of 10 T instead of an electromagnet generating 1 T, a small change of 1 mm is magnified to 10 cm and a phenomenon that takes a day to occur is completed in 15 min, because the magnetic effect is proportional to the square of the magnetic flux density. Diamagnetic levitation 2-4 and Moses effect 5 (water surface splits in a high magnetic field) are good examples among many others. [6][7][8][9] The magnetic effect on chemical reactions 10-12 is one of the major fields in magnetic researches, but in this paper we are concerned with the magnetic force and the magnetic torque acting on diamagnetic materials. The origin of the diamagnetism is the ...

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“…It is considered that the increase in the average elasticity was due to the increase in the crystalline regions of the gel, because of the alignment of the domains under the strong magnetic field. The increase in the number of linkage points and the volume of the crystalline regions might be related to the increase in the melting temperature of the ordered gel, as described in [3,4].…”

Section: Resultsmentioning

confidence: 97%

“…Such a gel shows an increase in the melting temperature [3,4], marked changes in its anisotropic properties [5,6], birefringence and anisotropic shrinkage, and an anisotropic increase in the electrophoresis velocity of DNA inside the gel. The results of the birefringence measurement indicated that the agarose molecule was ordered perpendicularly to the magnetic flux to which it was exposed.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic elasticity of magnetically ordered agarose gel

Yamamoto

Ozawa

Makino

et al. 2008

Science and Technology of Advanced Materials

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The physical properties of agarose gel prepared under strong magnetic fields were investigated. The storage modulus was measured by the reflection method with an ultrasonic pulse. The measurement results of the gel's elasticity indicate that agarose gel has anisotropic properties. The elasticity and its anisotropy depend on the concentration of the gel and the magnetic field to which it is exposed. The experimental results indicate that the anisotropic network structure of the gel is induced by the exposure to the magnetic field during gelation. The gelation mechanism under a magnetic field is discussed.

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Magnetic field effects on sol-gel phase changes in aqueous polymers

Cited by 20 publications

References 5 publications

The anisotropic properties of magnetically ordered gel

The anisotropic properties of magnetically ordered gel

Study on the Effect of Magnetic Fields on Polymeric Materials and Its Application

Anisotropic elasticity of magnetically ordered agarose gel

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