arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 0710.3433cond-mat.softcond-mat.mtrl-sci
收藏

三嵌段共聚物胶束形成体系的相行为和动力学

Phase behavior and dynamics of a micelle-forming triblock copolymer system

P. Harsha Mohan, Ranjini Bandyopadhyay

摘要:

Synperonic F-108(通用名,“pluronic”)是ABA型胶束形成三嵌段共聚物,其中A是聚环氧乙烷(PEO),B是聚环氧丙烷(PPO)。在高温下,PPO链的疏水性增加,并且当普朗尼克分子溶解在水性介质中时,自缔合成具有致密PPO核和水合PEO冠的球形胶束。在适当的高浓度下,这些胶束排列在面心立方晶格中以显示逆结晶,样品表现出高温结晶相和低温流体相。通过研究弹性模量和粘性模量随温度以固定速率升高的演化,我们构建了Synperonic F-108的浓度-温度相图。对于一定范围的温度和适当的样品浓度,我们观察到一个主要的弹性响应。对这些样品的振荡应变振幅扫描测量显示出损耗模量的明显峰值,这是软固体的典型特征。通过测量这些材料的频率依赖性机械模量,进一步证明了这些材料的软固体性质。储能模量明显大于损耗模量,并且几乎与所施加的角频率无关。最后,我们进行应变率频率叠加(SRFS)实验来测量这种软固体的慢松弛动力学。

英文摘要:

Synperonic F-108 (generic name, 'pluronic') is a micelle forming triblock copolymer of type ABA, where A is polyethylene oxide (PEO) and B is polypropylene oxide (PPO). At high temperatures, the hydrophobicity of the PPO chains increase, and the pluronic molecules, when dissolved in an aqueous medium, self-associate into spherical micelles with dense PPO cores and hydrated PEO coronas. At appropriately high concentrations, these micelles arrange in a face centred cubic lattice to show inverse crystallization, with the samples exhibiting high-temperature crystalline and low-temperature fluidlike phases. By studying the evolution of the elastic and viscous moduli as temperature is increased at a fixed rate, we construct the concentration-temperature phase diagram of Synperonic F-108. For a certain range of temperatures and at appropriate sample concentrations, we observe a predominantly elastic response. Oscillatory strain amplitude sweep measurements on these samples show pronounced peaks in the loss moduli, a typical feature of soft solids. The soft solid-like nature of these materials is further demonstrated by measuring their frequency dependent mechanical moduli. The storage moduli are significantly larger than the loss moduli and are almost independent of the applied angular frequency. Finally, we perform strain rate frequency superposition (SRFS) experiments to measure the slow relaxation dynamics of this soft solid.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑