Phase behaviors of cyclic diblock copolymers

Zhong-Yong, Fan; Yu, Yongtae; Qiu, Feng

doi:10.1063/1.3657437

Cited by 25 publications

(28 citation statements)

References 37 publications

(52 reference statements)

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“…More specifically, the domain spacing is reduced 71.1-72.8% compared to the lamellar domain spacing in the l-BCP thin film, which is 1.9-2.4 times greater than those theoretically predicted for cyclic BCPs. [38][39][40] In addition, the observed g-factor is approximately one third that of l-BCP, indicating that Bicycle-A forms a welldefined lamellar structure with a higher structural integrity than l-BCP. Moreover, the horizontal lamella formed by Bicycle-A exhibits a unidirectional orientation, which is significantly different from the lamellar structure of its l-BCP counterpart, which exhibits a mixture of horizontal and vertical orientations.…”

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Bicyclic Topology Transforms Self-Assembled Nanostructures in Block Copolymer Thin Films

et al. 2020

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Ongoing efforts in materials science have resulted in linear block copolymer systems that generate nanostructures via the phase-separation of immiscible blocks; however, such systems are limited with regard to their domain miniaturization and lack of orientation control. We overcome these limitations through the bicyclic topological alteration of a block copolymer system.Grazing incidence X-ray scattering analysis of nanoscale polymer films revealed that bicyclic topologies achieve 51.3-72.8% reductions in domain spacing when compared against their linear analogue, which is more effective than the theoretical predictions for conventional cyclic topologies. Moreover, bicyclic topologies achieve unidirectional orientation and a morphological transformation between lamellar and cylindrical domains with a high structural integrity.Considering the near equivalent volume fraction between the blocks, the formation of hexagonally packed cylindrical domains is particularly noteworthy. Bicyclic topological alteration is therefore a powerful strategy for developing advanced nanostructured materials for microelectronics, displays, and membranes.

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“…37 Overall, these domain spacing reductions are less than those (3037%) predicted theoretically. [38][39][40] In search for other effective approaches that substantially downsize BCP domains, strategies involving other variations of cyclic topology such as bicyclic or tricyclic, have not been investigated experimentally or theoretically as of yet.…”

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Bicyclic Topology Transforms Self-Assembled Nanostructures in Block Copolymer Thin Films

et al. 2020

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“…So far, there are some experimental, theoretical, and simulation studies on the comparison of the phase behaviors between linear and cyclic coil-coil diblock copolymer. [19][20][21] Therefore, the cyclic architecture in RC block copolymer is expected to effect the thermodynamically stable self-assembled structures and the details of the molecular packing.…”

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Self-assembly of cyclic rod-coil diblock copolymers

Chen

Zhang

et al. 2013

The Journal of Chemical Physics

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The phase behavior of cyclic rod-coil diblock copolymer melts is investigated by the dissipative particle dynamics simulation. In order to understand the effect of chain topological architecture better, we also study the linear rod-coil system. The comparison of the calculated phase diagrams between the two rod-coil copolymers reveals that the order-disorder transition point (χN)ODT for cyclic rod-coil diblock copolymers is always higher than that of equivalent linear rod-coil diblocks. In addition, the phase diagram for cyclic system is more "symmetrical," due to the topological constraint. Moreover, there are significant differences in the self-assembled overall morphologies and the local molecular arrangements. For example, frod = 0.5, both lamellar structures are formed while rod packing is different greatly in cyclic and linear cases. The lamellae with rods arranged coplanarly into bilayers occurs in cyclic rod-coil diblocks, while the lamellar structure with rods arranged end by end into interdigitated bilayers appears in linear counterpart. In both the lamellar phases, the domain size ratio of cyclic to linear diblocks is ranged from 0.63 to 0.70. This is attributed to that the cyclic architecture with the additional junction increases the contacts between incompatible blocks and prevents the coil chains from expanding as much as the linear cases. As frod = 0.7, the hexagonally packed cylinder is observed for cyclic rod-coil diblocks, while liquid-crystalline smectic A lamellar phase is formed in linear system. As a result, the cyclization of a linear rod-coil block copolymer can induce remarkable differences in the self-assembly behavior and also diversify its physical properties and applications greatly.

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“…1994 年, Matsen 等 [29] 用自洽场方法得到线型两嵌段高分子的相图. 而后, 自洽场方法被广泛地运用于各种不同拓扑结构的嵌段高分子的分相行为研究中, 如线型 [30] 、星型 [31] 、梳型 [32] 、环型 [33,34] 等. 最近, 谢楠等 [35] 用自洽场理论研究了 AB m 杂臂星型高分子的微相分离行为, 在相图上找到了复杂的 A15 相和 σ 相等三维球状相.…”

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“…Marko [38] 用标度律方法得到, 本体中环型两嵌段链比线型链更难分相, 临界相变点(χN)是等长线型链的 1.7 倍, 并且强分凝条件下层状相周期是线型链的 2 -2/3 倍. Grosberg 等 [39,40] 得到不具有体积排除的环型高分子的均方回转半径 R g 与链节数 N 的标度律关系为 R g ～N v , v≈0.588, 与具有体积排除的线型分子相同. Matsushita 等 [41] 用蒙特卡洛方法得到了环型高分子的第二维里系数是正数, 并且其均方回转半径远小于同分子量的线型链. 张国杰等 [33] 使用自洽场理论得到环型两嵌段高分子的相图, 发现环型链比线型链更难相分离, 并且结构周期是对应的线型链的 0.67 倍左右.…”

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A Strong Segregation Theory for Ring Block Copolymers

Liu¹,

Yang²,

Qiu³

2017

Acta Chim. Sinica

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Due to the ring structure with no free ends, the traditional strong-segregation theory for linear chains is not adequate for ring block copolymers. We developed the strong-segregation theory for ring block copolymers (SST-ring), by modifying both the entropic free energy term and the interfacial energy term. The ring block copolymer can only form two types of conformations, i.e., the loops on one side of an interface and the bridges connecting two interfaces. For the entropic energy originating from the stretching of the chain conformation under strong-segregation limit, we employ the strategy for calculating the entropic energy of looping and bridging chains connecting interfaces. Since the mixing of components is unavoidable for the ring triblock copolymers to adapt to the classical morphologies, we start from the propagating function of the self-consistent field theory, and deduce the formula of the interfacial energy between two two-component domains under the strong-segregation limit. The formula is reminiscent to the interfacial energy between two single-component domains, except that the Flory-Huggins parameter AB χ between two components on each side of the interface is replaced by an effective parameter, eff χ , which is a function of the composite fractions and the Flory-Huggins parameters between each components. The application of SST-ring to ring diblock copolymers is successful to describe the decreased characteristic length and the lifted order-disorder transition point, compared with the corresponding linear diblock copolymers with the same segment number N. We find that the critical AB N χ value of the ordered-disordered transition is 1.59 times that of the linear diblock polymers, and the characteristic lengths of the ring diblock copolymers are always 0.63 times of those of linear diblock copolymers. This agrees qualitatively with the predictions of the self-consistent theory, with slight quantitative difference originating from the strong-segregation limit assumption. For the SST-ring calculations for ring triblock copolymers in two-dimensions, corresponding to the film with the thickness much smaller than the radius of gyration of the polymer, we consider two types of micro phase structures: the classical morphologies (lamellae and cylinders) with multi-component domains, and the tiling-brick structures ([6,6,6] and [8,8,4], where the numbers denote the side numbers of the bricks) consisting of the single-component domains. SST-ring predicts that the ternary diagram consists of both types of the micro phase structures. When the Flory-Huggins parameters between any two components are equal, the phase diagram has a three-fold rotational symmetry to the center of the regular triangle, and three mirror symmetric axis crossing three vertices of the triangle, respectively. Our SST-ring theory is easy to be applied to different morphologies of ring block copolymers.

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Phase behaviors of cyclic diblock copolymers

Cited by 25 publications

References 37 publications

Bicyclic Topology Transforms Self-Assembled Nanostructures in Block Copolymer Thin Films

Bicyclic Topology Transforms Self-Assembled Nanostructures in Block Copolymer Thin Films

Self-assembly of cyclic rod-coil diblock copolymers

A Strong Segregation Theory for Ring Block Copolymers

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