Largely Tunable Asymmetry of Phase Diagrams of A(AB)(n) Miktoarm Star Copolymer
Largely Tunable Asymmetry of Phase Diagrams of A(AB)(n) Miktoarm Star Copolymer
复制标题
A(AB)(n) Miktoarm 星形共聚物相图的很大程度上可调节的不对称性
DOI：
10.1021/acs.macromol.0c02272
复制
发表时间：
2020
期刊：
影响因子：
5.5
通讯作者：
Li Weihua
中科院分区：
文献类型：
--
作者：
Li Congcong;Dong Qingshu;Li Weihua
拓扑不对称性是AB型嵌段共聚物相图相对于A嵌段体积分数由对称变为不对称的重要因素。然而，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，如(AB)NStar和ABnmiktoarm星形共聚物。本文用自洽场理论研究了由一个A1臂和一个A2B臂组成的A1(A2B)nmiktoarm星形共聚物的自组装行为，目的是证明相图的不对称性可以通过控制来很大程度地调节，并且A1-嵌段的体积分数fA1与A-链段的总体积分数之比τ=fa1/f。注意到这种τ=0的共聚物被还原为(AB)nStar共聚物，而τ=1。对于≥2，相图的不对称性发生非单调变化，并且随着τ从0增加到1，呈现最大值。最大不对称度随n的增大而增大。在n=5时的最大不对称性相图中，在中等偏析强度下，A球/A柱体和A陀螺体/薄片的相界分别偏转到≈0.56和≈0.76。结果，在这种高度不对称的相图中，Frank-Kasperσ和A15相的区域都急剧扩大。此外，随着τ的增加，陀螺体区域呈现出非常复杂的变化趋势，甚至在τ=≥3的一定范围内消失。令人惊讶的是，具有优化τ≈0.6的A1(A2B)3共聚物在ΔN=60时呈现出最大的陀螺体区域，宽度约为ΔFG≈0.187，约是χ=0时的4倍和τ=1时的13倍。这种通道体积分数为f≈0.54t/≈0.73的陀螺体形态具有很好的应用前景。
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)nstar and ABnmiktoarm star copolymers. In this work, we investigate the self-assembly behavior of an A1(A2B)nmiktoarm star copolymer composed of one A1-arm andnA2B-arms using self-consistent field theory, aiming to demonstrate that the asymmetry of the phase diagram can be largely tuned by controllingnand the ratio of the volume fractionfA1of A1-block to the total volume fractionfof A-blocks, τ =fA1/f. Note that this copolymer with τ = 0 is reduced to (AB)nstar copolymer while it is reduced to ABnmiktoarm star copolymer with τ = 1. Forn≥ 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 increasingn. In the phase diagram of maximal asymmetry withn= 5, the phase boundaries of A-sphere/A-cylinder and A-gyroid/lamella are deflected tof≈ 0.56 andf≈ 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 forn≥ 3. Surprisingly, the A1(A2B)3copolymer with an optimized τ ≈ 0.6 exhibits the largest gyroid region with a width of about ΔfG≈ 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 fromf≈ 0.54 tof≈ 0.73 is promising in applications.