Irreversible Shear-Activated Gelation of a Liquid Crystalline Polyelectrolyte
Irreversible Shear-Activated Gelation of a Liquid Crystalline Polyelectrolyte
复制标题
液晶聚电解质的不可逆剪切激活凝胶化
DOI：
10.1021/acsmacrolett.0c00168
复制
发表时间：
2020
影响因子：
7.015
通讯作者：
Dingemans, Theo J.
中科院分区：
文献类型：
--
作者：
Fox, Ryan J.;Hegde, Maruti;Zanelotti, Curt J.;Kumbhar, Amar S.;Samulski, Edward T.;Madsen, Louis A.;Picken, Stephen J.;Dingemans, Theo J.
我们报告了刚性聚电解质液晶溶液中不可逆的剪切激活凝胶化，该溶液在无盐溶液中形成棒状组装体（棒）。在静止时，液晶溶液对凝胶化是动力学稳定的，并且表现出低粘度。在处于或高于临界剪切速率的稳定剪切下，由于杆的线性生长和分支，形成物理交联的凝胶网络。在临界剪切速率以上，凝胶化的时间尺度可以通过改变剪切速率和溶液浓度从数小时调整到几乎瞬间。剪切激活凝胶在结构和流变学性质上与热可逆凝胶不同。在固定浓度下，凝胶化前的诱导时间随剪切速率呈指数下降。这一结果表明，静电稳定棒的剪切激活热化克服了棒-棒接触的能量势垒，使棒融合和随后的不可逆网络形成。
We report irreversible, shear-activated gelation in liquid crystalline solutions of a rigid polyelectrolyte that forms rodlike assemblies (rods) in salt-free solution. At rest, the liquid crystalline solutions are kinetically stable against gelation and exhibit low viscosities. Under steady shear at, or above, a critical shear rate, a physically cross-linked, nematic gel network forms due to linear growth and branching of the rods. Above a critical shear rate, the time scale of gelation can be tuned from hours to nearly instantaneously by varying the shear rate and solution concentration. The shear-activated gels are distinct in their structure and rheological properties from thermoreversible gels. At a fixed concentration, the induction time prior to gelation decreases exponentially with the shear rate. This result indicates that shear-activated thermalization of the electrostatically stabilized rods overcomes the energy barrier for rod–rod contact, enabling rod fusion and subsequent irreversible network formation.