Direct Observation of Relaxation of Aqueous Shake-Gel Consisting of Silica Nanoparticles and Polyethylene Oxide
Direct Observation of Relaxation of Aqueous Shake-Gel Consisting of Silica Nanoparticles and Polyethylene Oxide
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DOI：
10.3390/polym12051141
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发表时间：
2020-05-01
期刊：
影响因子：
5
通讯作者：
Kobayashi, Motoyoshi
中科院分区：
文献类型：
--
作者：
Huang, Yi;Kobayashi, Motoyoshi
在工业生产中，控制由胶体颗粒和聚合物组成的悬浮液的流变性是非常必要的。特别是剪切诱导凝胶（摇凝胶）是流变学领域中的一种有趣现象。为了深入了解二氧化硅纳米粒子和聚氧化乙烯（PEO）的水悬浮液的摇凝胶现象及其随时间的变化，我们观察了二氧化硅-PEO悬浮液的状态转变并测量了其粘度。结果表明，PEO用量、pH值和PEO分子量对悬浮状态有很大的影响，并揭示了悬浮状态的差异，即混浊、永久凝胶、振荡凝胶和高粘度溶胶。我们发现，从振动凝胶到可流动的溶胶的弛豫时间增加到最大值，并再次减少与PEO剂量的增加。pH值为8.4时的凝胶松弛速度比pH值为9.4时慢，pH值大于10时，大多数情况下不形成凝胶，表明pH值过高会抑制凝胶的形成。分子量为1000和4000 kDa的PEO很容易通过架桥结合更多的二氧化硅纳米颗粒，并导致形成具有更稳定聚合物网络的凝胶。分子量为1000和4000 kDa的PEO也导致二氧化硅-PEO悬浮液从凝胶到溶胶的较长弛豫时间。
Controlling the rheological property of suspensions consisting of colloidal particles and polymers is necessary in industry. Especially, gels induced by shear (shake-gel) are interesting phenomena in rheological field. To gain insight into the shake-gel phenomena of the aqueous suspensions of silica nanoparticles and poly(ethylene oxide) (PEO) and its temporal change, we observed the state transition and measured the viscosity of the silica-PEO suspensions. Our results showed that PEO dose, pH, and molecular weight of PEO influence the state of suspension greatly, and revealed the differences of the suspension states, namely, cloudy, permanent gel, shake-gel, and high viscosity sol. We found that the relaxation time from shake-gel to flowable sol increases to the maximum and decreases again with increasing PEO dose. Shake-gels at pH 8.4 relaxed more slowly than at pH 9.4, and shake-gel did not form at pH above 10 in most of cases, indicating high pH inhibits the formation of shake-gels. PEO of molecular weight of 1000 and 4000 kDa easily bonds more silica nanoparticles by bridging and results in the formation of gels with more stable polymer networks. PEO of molecular weight of 1000 and 4000 kDa also led to longer relaxation time of the silica-PEO suspensions from gel to sol.