Rheological characteristics of mesophases of block copolymer solutions
Rheological characteristics of mesophases of block copolymer solutions
复制标题
嵌段共聚物溶液中间相的流变特性
作者：
Sahar Qavi;R. Foudazi
嵌段共聚物在溶剂存在下自组装形成有序中间相结构，也称为溶致液晶（LLC）。这项工作的目的是研究具有层状和六角结构的 Pluronic 嵌段共聚物/水/油中间相的流变特性。层状和六方中间相的流动行为表明它们具有屈服应力。振荡剪切实验表明中间相具有类固体行为并表现出 III 型非线性行为。中间相的弹性模量可能由胶束之间的范德华相互作用控制。我们认为，在相对较低的频率下，缺陷控制着 LLC 的流变行为，而在高频下，胶束尺度的贡献占主导地位。对 LLC 施加高应变会在停止流动后产生两个弛豫时间，降低整个频率范围内的储能模量，并降低小频率范围内的损耗模量，而在高频下的影响可以忽略不计。模量的降低是可逆的，系统松弛回到其原始的静止弹性模量。观察到的行为可归因于高应变下缺陷的消除以及在足够长的休息时间内缺陷的重新形成。
Self-assembly of block copolymers in the presence of solvents forms ordered mesophase structures, also known as lyotropic liquid crystals (LLCs). The aim of this work is to investigate the rheological properties of Pluronic block copolymer/water/oil mesophases with lamellar and hexagonal structures. The flow behavior of lamellar and hexagonal mesophases indicates that they have yield stress. Oscillatory shear experiments show that mesophases have solid-like behavior and exhibit type III non-linear behavior. The elastic modulus of mesophases is probably controlled by the van der Waals interaction between micelles. We suggest that at relatively low frequencies, defects control the rheological behavior of LLCs, while at high frequencies, the contributions in micellar scale are dominant. Applying high strains on the LLCs induces two relaxation times after cessation of flow, decreases the storage modulus in the whole frequency range, and decreases the loss modulus in small-frequency regime with negligible effect at high frequencies. The decrease in moduli is reversible and the system relaxes back to its original elastic modulus at rest. The observed behavior can be attributed to the elimination of defects under high strains and their re-formation during long enough rest times.
影响因子：
41.2
作者：
Nie, Zhihong;Fava, Daniele;Rubinstein, Michael
通讯作者：
Rubinstein, Michael