Soft glassy colloidal arrays in an ionic liquid: colloidal glass transition, ionic transport, and structural color in relation to microstructure.
Soft glassy colloidal arrays in an ionic liquid: colloidal glass transition, ionic transport, and structural color in relation to microstructure.
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DOI：
10.1021/jp106872w
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发表时间：
2010-10
期刊：
影响因子：
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通讯作者：
K. Ueno;Y. Sano;A. Inaba;Masashi Kondoh;M. Watanabe
中科院分区：
文献类型：
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作者：
K. Ueno;Y. Sano;A. Inaba;Masashi Kondoh;M. Watanabe
研究了由聚甲基丙烯酸甲酯(PMMA)接枝二氧化硅纳米颗粒(PMMA-g-NPs)和室温离子液体1-乙基-3-甲基咪唑双(三氟甲烷磺酰)酰胺([C(2)mim][NTF(2)])组成的软玻璃胶体阵列(SGCA)的胶体玻璃化转变、离子输运和光学性质。在较低的粒子浓度下，PMMA-g-NPs在IL中能很好地悬浮，没有任何聚集或沉淀，稀释液表现出类似液体的行为。然而，在一定的颗粒浓度以上，悬浮液就会固化，并根据颗粒浓度的不同表现出不同的结构颜色。SGCA的液-固转变主要是由胶体玻璃化转变引起的。由于粒子之间的软排斥作用，胶体玻璃化转变所需的粒子的有效体积分数(ϕ(Ef))比硬球系统的高，约为0.70-0.74。SGCA具有足够的离子电导率，在室温下，即使在高浓度区域，其离子电导率也大于10(-3)S厘米(-1)。对于阳离子和阴离子在SGCA中的离子传输，[NTF(2)]阴离子的扩散系数随粒子(D(G)/D(0))的加入而下降的幅度略大于[C(2)mim]阳离子，表明[NTF(2)]阴离子优先与PMMA链相互作用。在玻璃化转变体积分数以上，SGCA显示出均匀的、非明亮的、与角度无关的结构颜色。此外，随着颗粒浓度的增加，SGCA的颜色由红色变为绿色再变为蓝色。在SGCA中，反射光谱的最大波长与中心到中心的距离之间存在线性关系。
The colloidal glass transition, ionic transport, and optical properties of soft glassy colloidal arrays (SGCAs) that consist of poly(methyl methacrylate) (PMMA)-grafted silica nanoparticles (PMMA-g-NPs) and a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethane sulfonyl)amide ([C(2)mim][NTf(2)]), were investigated. At lower particle concentrations, PMMA-g-NPs were well-suspended in the IL without any aggregation or sedimentation, and the dilute suspensions showed liquid-like behavior. However, above a certain particle concentration, the suspensions became solidified and exhibited different structural colors depending on the particle concentrations. The liquid-solid transition of the SGCAs was essentially caused by colloidal glass transition. Due to the soft repulsive interaction between the particles, the effective volume fraction of the particle (ϕ(eff)) required for colloidal glass transition was higher than that of the hard sphere system and found to be approximately 0.70-0.74. The SGCA had sufficient ionic conductivity, which was greater than 10(-3) S cm(-1) at room temperature, even in the highly concentrated region. For ionic transport of the cation and the anion in the SGCAs, the decrease in diffusivity observed with the addition of the particles (D(g)/D(0)) was slightly greater for the [NTf(2)] anion than that of the [C(2)mim] cation, suggesting that the [NTf(2)] anion preferentially interacts with the PMMA chains. The SGCAs showed homogeneous, nonbrilliant, and angle-independent structural colors above the glass transition volume fraction. In addition, the color of the SGCAs changed from red to green to blue as the particle concentration increased. A linear relationship was found between the maximum wavelength of the reflection spectra and the center-to-center distance in the SGCAs.