Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854, USA.
J Chem Phys. 2011 Feb 7;134(5):054104. doi: 10.1063/1.3532831.
The self-consistent field theory (SCFT) complemented with the Poisson-Boltzmann equation is employed to explore self-assembly of polyelectrolyte copolymers composed of charged blocks A and neutral blocks B. We have extended SCFT to dissociating triblock copolymers and demonstrated our approach on three characteristic examples: (1) diblock copolymer (AB) melt, (2) symmetric triblock copolymer (ABA) melt, (3) triblock copolymer (ABA) solution with added electrolyte. For copolymer melts, we varied the composition (that is, the total fraction of A-segments in the system) and the charge density on A blocks and calculated the phase diagram that contains ordered mesophases of lamellar, gyroid, hexagonal, and bcc symmetries, as well as the uniform disordered phase. The phase diagram of charged block copolymer melts in the charge density--system composition coordinates is similar to the classical phase diagram of neutral block copolymer melts, where the composition and the Flory mismatch interaction parameter χ(AB) are used as variables. We found that the transitions between the polyelectrolyte mesophases with the increase of charge density occur in the same sequence, from lamellar to gyroid to hexagonal to bcc to disordered morphologies, as the mesophase transitions for neutral diblocks with the decrease of χ(AB). In a certain range of compositions, the phase diagram for charged triblock copolymers exhibits unexpected features, allowing for transitions from hexagonal to gyroid to lamellar mesophases as the charge density increases. Triblock polyelectrolyte solutions were studied by varying the charge density and solvent concentration at a fixed copolymer composition. Transitions from lamellar to gyroid and gyroid to hexagonal morphologies were observed at lower polymer concentrations than the respective transitions in the similar neutral copolymer, indicating a substantial influence of the charge density on phase behavior.
自洽场理论（SCFT）与泊松-玻尔兹曼方程相结合，用于探索由带电嵌段 A 和中性嵌段 B 组成的聚电解质共聚物的自组装。我们已经将 SCFT 扩展到离解三嵌段共聚物，并在三个典型示例上证明了我们的方法：（1）嵌段共聚物（AB）熔体，（2）对称三嵌段共聚物（ABA）熔体，（3）添加电解质的三嵌段共聚物（ABA）溶液。对于共聚物熔体，我们改变了组成（即系统中 A 段的总分数）和 A 嵌段上的电荷密度，并计算了包含层状、向列、六方和 bcc 对称有序介相以及均匀无序相的相图。带电嵌段共聚物熔体在电荷密度-系统组成坐标中的相图与中性嵌段共聚物熔体的经典相图相似，其中组成和 Flory 失配相互作用参数 χ(AB) 用作变量。我们发现，随着电荷密度的增加，聚电解质介相之间的转变发生在相同的顺序中，从层状到向列到六方到 bcc 到无序形态，与 χ(AB) 降低的中性二嵌段的介相转变相同。在一定的组成范围内，带电三嵌段共聚物的相图表现出意想不到的特征，允许随着电荷密度的增加从六方到向列到层状介相转变。通过改变电荷密度和溶剂浓度在固定共聚物组成下研究了三嵌段聚电解质溶液。在比类似的中性共聚物中相应转变更低的聚合物浓度下观察到从层状到向列和向列到六方形态的转变，表明电荷密度对相行为有实质性影响。
