Morphology Transitions of Linear A₁B₁A₂B₂ Tetrablock Copolymers at Symmetric Overall Volume Fraction

Abstract

We investigated morphology transitions of linear tetrablock copolymers of polystyrene-block-polyisoprene-block-polystyrene-block-polyisoprene (S1I1S2I2) by varying volume fraction of PI1 block (f PI1), while maintaining the symmetric volume fraction of total PS blocks and PI blocks (f PS1+f PS2:f PI1+f PI2 ≈ 1:1). An interesting sequence of morphology transitions was observed as f PI1 was increased: lamellae (L) → asymmetric lamellae (aL) → hexagonally packed PI-cylinders (CPI) → double gyroid with PI-network domains (GPI) → short-period lamellae (sL). The domain spacing of sL was nearly half that of L, while aL had asymmetric lamellar width of PS and PI microdomains. It is particularly interesting that cylindrical and gyroid morphologies were observed in linear block copolymers with symmetric overall volume fraction at intermediate segregation. The experimentally observed morphologies are in good agreement with the predicted equilibrium phases by self-consistent field theory (SCFT).

“Bridge” Makes Differences to the Self-assembly of Block Copolymers

“…American Chemical Society). [30][31][46][47][48] . 例 如 , Miyamori 等 [48] 在 ABAC 体系中观察了类十二轴准晶结 构, "拉伸桥连效应"对该结构的形成起到了关键作用, 证实了我们的理论预测 [25]…”

“…一 方面, 发展了场的特殊初始化方法, 解决了复杂结构的 求解难题 [15] ; 另一方面, 利用结构空间对称性对准谱方 法进行了加速 [16] . 高效精确的自洽场计算使我们可以 开展系统深入的理论研究, 不仅加深了对实验结果的理 解 [17][18][19][20][21][22] , 所预测的新结果还促进了新的实验研究 [23][24][25][26][27][28][29][30][31][32][33] . 因此, 实验和理论的相互促进将嵌段共聚物自组装的研 究不断向前推进.…”

Fabrication of Ultrafine, Highly Ordered Nanostructures Using Carbohydrate-Inorganic Hybrid Block Copolymers

“…When N ABA = N AB , the microphase-separated morphology and dimension of ABA-type triblock copolymers are comparable to those of AB-type diblock copolymers. In other words, d of an ABA-type triblock copolymer is half that of an AB-type diblock copolymer with the same molecular weight [ 58 ]. Thus, using the organic–inorganic hybrid triblock copolymer architecture would be extremely advantageous for forming ultrafine microphase-separated structures without sacrificing the molecular weight of BCP.…”

Self‐Assembly of Nonfrustrated ABCBA Linear Pentablock Terpolymers

“…[ 23,24 ] More complex microstructures of AB diblock copolymers have been discovered under certain conditions from recent experiments and simulations, including the helical structures [ 25–28 ] and the Frank–Kasper σ phase. [ 29 ] Besides, with the advance in synthetic techniques, adding a third component [ 3–7,30–55 ] and/or modifying the block numbers [ 8–13,16–18,56–68 ] to the linear block chains could be achieved. The more complex block copolymers provide opportunities to obtain diverse morphologies.…”

“…Apart from these observations in the triblock terpolymers, recently much attention focuses on exploring novel self‐assembly structures by extending the block numbers, designing the block sequences and varying the compositions on the linear block chains. [ 8–13,16–18,56–68 ] One particularly interesting extension of a linear ABC triblock copolymer is the symmetric ABCBA pentablock terpolymer. This class of multiblock copolymers could exhibit rich self‐assembly behaviors and enhance mechanical properties of the material.…”