Topological asymmetry is an important factor to change the phase diagram of AB-type block copolymer with respect to the volume fraction of A-blocks from symmetric to asymmetric. However, many topology-asymmetric AB-type block copolymers can only produce limited effects on the asymmetry of phase diagrams, such as (AB)_n star and AB_n miktoarm star copolymers. In this work, we investigate the self-assembly behavior of an A₁(A₂B)_n miktoarm star copolymer composed of one A₁-arm and n A₂B-arms using self-consistent field theory, aiming to demonstrate that the asymmetry of the phase diagram can be largely tuned by controlling n and the ratio of the volume fraction f_A1 of A₁-block to the total volume fraction f of A-blocks, τ = f_A1/f. Note that this copolymer with τ = 0 is reduced to (AB)_n star copolymer while it is reduced to AB_n miktoarm star copolymer with τ = 1. For n ≥ 2, the asymmetry of the phase diagram changes nonmonotonically and exhibits a maximum as τ increases from 0 to 1, and the maximal degree of asymmetry increases with increasing n. In the phase diagram of maximal asymmetry with n = 5, the phase boundaries of A-sphere/A-cylinder and A-gyroid/lamella are deflected to f ≈ 0.56 and f ≈ 0.76 at a moderate segregation strength, respectively. As a result, the regions of both Frank–Kasper σ and A15 phases are dramatically expanded in such a highly asymmetric phase diagram. Moreover, the gyroid region exhibits a very complex changing trend with increasing τ, even vanishing in a certain range of τ for n ≥ 3. Surprisingly, the A₁(A₂B)₃ copolymer with an optimized τ ≈ 0.6 exhibits the largest gyroid region with a width of about Δf_G ≈ 0.187 at χN = 60, which is about 4 times that at τ = 0 and 13 times that at τ = 1. The gyroid morphology with the volume fraction of channels ranging from f ≈ 0.54 to f ≈ 0.73 is promising in applications.

中文翻译：

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A（AB）_n Miktoarm星型共聚物相图的可调谐不对称性

相对于A-嵌段的体积分数，AB型嵌段共聚物的相图从对称改变为不对称是拓扑不对称的重要因素。但是，许多拓扑不对称的AB型嵌段共聚物只能对相图的不对称性产生有限的影响，例如（AB）_n star和AB _n miktoarm star共聚物。在这项工作中，我们使用自洽场理论研究由1个A ₁臂和n A ₂ B臂组成的A ₁（A ₂ B）_n纳米臂星形共聚物的自组装行为，旨在证明相图的不对称性可以通过控制n和A ₁块的体积分数f _{A 1}与A块的总体积分数f之比τ= f _{A 1} / f。请注意，此共聚物与τ= 0减小到（AB）_ñ而它被减小到AB星形共聚物_Ñ与τ= 1。对于杂臂星形共聚物Ñ ≥2时，相图的不对称性nonmonotonically改变并显示出最大的τ从0增加到1，并且最大不对称度随着n的增加而增加。在具有n的最大不对称性的相图中= 5，A-球/ A缸和A-螺旋形/薄片的相界被偏转到˚F ≈0.56和˚F分别≈0.76以适中的分离强度，。结果，在这种高度不对称的相图中，Frank–Kasperσ和A15相的区域都显着扩展。此外，螺旋形区域表现出与增加的τ，甚至在一定范围内的τ为消失一个非常复杂的变化趋势Ñ ≥3.令人惊讶地，将A ₁（A ₂ B）₃共聚物具有优化τ≈0.6展品最大螺旋形具有约Δ的宽度区域˚F _ģ ≈0.187在χ ñ= 60，这是约4倍，在τ= 0和13倍，在τ= 1具有通道，从体积分数的螺旋形态˚F ≈0.54〜˚F ≈0.73在应用前途。