Effect of Particles Alignment on Giant Reduction in Dynamic Modulus of Hydrogels Containing Needle-Shaped Magnetic Particles
Effect of Particles Alignment on Giant Reduction in Dynamic Modulus of Hydrogels Containing Needle-Shaped Magnetic Particles
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DOI：
10.1007/978-3-642-00865-8_23
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
T. Mitsumata;Y. Kosugi;S. Ouchi
中科院分区：
文献类型：
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作者：
T. Mitsumata;Y. Kosugi;S. Ouchi
我们研究了具有定向粒子的磁性凝胶的动态模量的巨大降低。磁性凝胶是由κ-卡拉胶凝胶负载γ-Fe 2 O3颗粒组成的，颗粒的纵横比为1.8。在凝胶化过程中，磁性颗粒通过50 mT的弱磁场排列。具有对准颗粒的凝胶表现出由于磁化而在106 Pa的量级上的储能杨氏模量的巨大降低;然而，对于具有随机颗粒的凝胶，没有观察到储能模量的降低。具有排列颗粒的凝胶的储能模量在体积分数为0.01以上不遵循Halpin-Tsai方程，表明磁性颗粒的非均匀分散;然而，具有随机颗粒的凝胶的模量在所有体积分数下满足方程，表明颗粒的随机分散。有人指出，与对齐的颗粒的凝胶表现出增强的非线性粘弹性和大值的损耗角正切，而与随机颗粒的凝胶表现出弱的非线性粘弹性和小值的损耗角正切。这表明磁性颗粒在凝胶中形成具有对齐颗粒的颗粒网络。有人还发现，磁性凝胶与排列的颗粒没有经历一个显着的降低储能模量时，施加磁场平行于磁性颗粒的排列。这有力地表明，动态模量的巨大降低是由于破坏了磁性凝胶中形成的颗粒网络。
We investigated the giant reduction in the dynamic modulus of magnetic gels with aligned particles. The magnetic gel is consisting of a κ-carrageenan gel loaded with γ-Fe2O3particles with an aspect ratio of ∼8. The magnetic particles were aligned by a weak magnetic field of 50 mT during gelation. The gels with aligned particles demonstrated giant reductions in the storage Young’s modulus on the order of 106Pa due to magnetization; however, no reductions in the storage modulus were observed for the gels with random particles. The storage modulus of gels with aligned particles did not follow the Halpin-Tsai equation above volume fractions of 0.01, indicating the heterogeneous dispersion of the magnetic particles; however, the modulus of the gels with random particles satisfied the equation at all volume fractions, suggesting the random dispersion of the particles. It was noted that the gels with aligned particles demonstrated enhanced nonlinear viscoelasticity and a large value of the loss tangent, while the gels with random particles exhibited weak nonlinear viscoelasticity and a small value of the loss tangent. This indicates that the magnetic particles form a particle network in the gel with aligned particles. It was also found that the magnetic gel with aligned particles did not undergo a marked reduction in the storage modulus when the magnetic field was applied in parallel with the alignment of magnetic particles. This strongly indicates that the giant reduction in dynamic modulus is caused by breaking the particle network developed in the magnetic gel.