Confined flows of a polymer microgel
Confined flows of a polymer microgel
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DOI：
10.1140/epje/i2013-13030-3
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发表时间：
2013-03-01
影响因子：
1.8
通讯作者：
Barentin, Catherine
中科院分区：
文献类型：
--
作者：
Geraud, Baudouin;Bocquet, Lyderic;Barentin, Catherine
在本文中，我们探讨了约束对聚合物微凝胶，即卡波普流动的影响。我们比较其体积流变行为，用流变仪测量和描述的赫谢尔-Bulkley定律，粗糙的微通道中测量的速度分布，获得与粒子跟踪测速技术。我们发现，速度分布的整体预测与微通道中的测量结果之间存在强烈的不一致。在最近引入的非局部流动性模型（J. Goyon等人，Nature，454，84（2008））的框架内成功地分析了受限条件下的速度分布。这允许确定协同性长度，其数量级与微凝胶的结构尺寸相当。此外，我们测量流动曲线，使用流变仪为不同的间隙条件，也表明，这组数据表现出很强的效果上测得的流变性能的限制。这再次以与协同性长度尺度相同量级的典型长度为特征。因此，我们的证据约束效应与两个互补的实验，这两个实验都给出了相同的典型长度的重排流。
In this paper, we probe the influence of confinement on the flows of a polymer microgel, namely Carbopol. We compare its bulk rheological behavior, measured with a rheometer and well described by a Hershel-Bulkley law, to velocity profiles measured in rough microchannels, obtained with a particle tracking velocimetry technique. We show a strong disagreement between the bulk prediction for the velocity profiles and the measured ones in the microchannels. Velocity profiles in confined conditions are successfully analyzed within the framework of a non-local fluidity model introduced recently (J. Goyon et al. Nature, 454, 84 (2008)). This allows to determine a cooperativity length., whose order of magnitude compares with the structure size of the microgel. Moreover, we measure flow curves using a rheometer for different gap conditions and also show that this set of data exhibit a strong effect of the confinement on the measured rheological properties. This is again characterized by a typical length of the same order as the cooperativity length scale.. We thus evidence confinement effects with two complementary experiments which both give the same typical length for the rearrangements in the flows.