Department of Chemical Engineering, Indian Institute of Technology Delhi, New Delhi 110 016, India.
Soft Matter. 2019 Oct 14;15(38):7623-7634. doi: 10.1039/c9sm01240k. Epub 2019 Sep 4.
The self-assembly behavior of brush-grafted nanoparticles in the ordered mesophase of a symmetric triblock copolymer is studied using the self-consistent field theory. The emphasis is on the templated localization of nanoparticles in a two-dimensional lamellar microstructure formed by an ABA triblock copolymer. While particles grafted with either A-type or B-type polymeric chains preferentially localize in the respective micro-domain, the spatial distribution of particles within the selective domain is of great interest in controlling the properties of the nano-ordered morphologies. As the mid-block of an ABA triblock copolymer is entropically constrained, the localization behavior of B-grafted nanoparticles is found to be qualitatively different from that of A-grafted particles. The absence of free ends and the bridge conformation of the mid-block tend to reduce the spatial segregation of B-grafted particles at the center of the B-domain, a behavior in contrast to an AB diblock copolymer. Under similar conditions, while A-grafted particles self-assemble at the center of the A-domain, the B-grafted particles with a non-selective core segregate predominantly at the interface of A and B domains, especially when the particle size is large or grafting is weak. Upon increasing the grafting density, the morphology transitions from interface to center localization. The spatial localization of particles, governed by the interplay of enthalpic and entropic contributions to the free energy, is found to be strongly influenced by particle size, selectivity, volume fraction, and number and size of grafted chains. Controlling the self-assembly behavior of particles by tuning these parameters will be immensely helpful in designing advanced nanostructured materials with desired physical properties.
使用自洽场理论研究了梳状接枝纳米粒子在对称三嵌段共聚物有序介相中的自组装行为。重点是在由 ABA 三嵌段共聚物形成的二维层状微结构中模板化定位纳米粒子。虽然接枝 A 型或 B 型聚合物链的粒子分别优先定位在各自的微区中，但在选择性域内粒子的空间分布对于控制纳米有序形态的性质非常重要。由于 ABA 三嵌段共聚物的中间嵌段受到熵约束，因此接枝 B 型纳米粒子的定位行为与接枝 A 型粒子的行为明显不同。中间嵌段无游离末端和桥构象，倾向于减少 B 型接枝粒子在 B 域中心的空间隔离，这种行为与 AB 二嵌段共聚物相反。在相似的条件下，当 A 型接枝粒子在 A 域中心自组装时，具有非选择性核的 B 型接枝粒子主要在 A 和 B 域的界面处分离，特别是当粒子尺寸较大或接枝较弱时。随着接枝密度的增加，形态从界面到中心定位转变。粒子的空间定位受自由能中焓和熵贡献的相互作用控制，强烈受到粒子尺寸、选择性、体积分数以及接枝链的数量和尺寸的影响。通过调整这些参数来控制粒子的自组装行为，将极大地有助于设计具有所需物理性质的先进纳米结构材料。
