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The size and affinity effect of counterions on self-assembly of charged block copolymers
The Journal of Chemical Physics ( IF 4.4 ) Pub Date : 2020-03-24 , DOI: 10.1063/5.0002896
Jiadi Jiang 1 , Xu Chen 1 , Shuang Yang 1 , Er-Qiang Chen 1
Affiliation  

The effect of counterions’ size and affinity on the microphase separated morphologies of neutral-charged diblock copolymers is investigated systematically using a random phase approximation (RPA) and self-consistent field theory (SCFT). The phase diagrams as a function of χAB and fA at different counterion sizes and different affinities to neutral blocks are constructed, respectively. Stability limits calculated using the RPA are in good agreement with the disorder-body-centered cubic phase boundaries from SCFT calculations. It was found that increasing the size of counterions causes the phase diagram to shift upward and leftward, which is attributed to electrostatic interactions and the intrinsic volume of counterions. The domain size of the ordered phase shows an unexpected tendency that it decreases with increasing counterions’ size. The counterions’ distributions in H and G phases demonstrate that it is electrostatic interaction, instead of packing frustration, that plays a leading role in such systems. For finite size counterions, with the increase in affinity between counterions and neutral blocks, the phase diagram shifts upward, indicating the improved compatibility between different blocks. Furthermore, the affinity effect between counterions and neutral blocks can be mapped into an effective Flory parameter χAB = χAB + 0.27χBC.

中文翻译:

平衡离子对带电嵌段共聚物自组装的尺寸和亲和力的影响

使用随机相近似(RPA)和自洽场理论(SCFT)系统地研究了抗衡离子的大小和亲和力对中性双嵌段共聚物微相分离形态的影响。相图的一个函数χ AB˚F分别以不同的抗衡离子大小和对中性嵌段的亲和力构建。使用RPA计算的稳定性极限与通过SCFT计算得出的以无序体为中心的立方相边界非常吻合。发现增加抗衡离子的尺寸会导致相图向上和向左移动,这归因于静电相互作用和抗衡离子的固有体积。有序相的畴尺寸显示出出人意料的趋势,其随抗衡离子尺寸的增加而减小。H和G相中抗衡离子的分布表明,在此类系统中起主要作用的是静电相互作用而不是堆积的挫败感。对于有限大小的抗衡离子,随着抗衡离子与中性嵌段之间亲和力的增加,相图向上移动,表明不同模块之间的兼容性得到改善。此外,抗衡离子与中性嵌段之间的亲和效应可以映射为有效的Flory参数χ一种= χ AB + 0.27 χ BC
更新日期:2020-03-31
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