Beránek Pavel, Posocco Paola, Posel Zbyšek
Department of Informatics, Faculty of Science, Jan Evangelista Purkyně University in Ústí nad Labem, 40096 Ústí nad Labem, Czech Republic.
Department of Engineering and Architecture, University of Trieste, 34127 Trieste, Italy.
Polymers (Basel). 2020 Oct 23;12(11):2462. doi: 10.3390/polym12112462.
Design and preparation of functional nanomaterials with specific properties requires precise control over their microscopic structure. A prototypical example is the self-assembly of diblock copolymers, which generate highly ordered structures controlled by three parameters: the chemical incompatibility between blocks, block size ratio and chain length. Recent advances in polymer synthesis have allowed for the preparation of gradient copolymers with controlled sequence chemistry, thus providing additional parameters to tailor their assembly. These are polydisperse monomer sequence, block size distribution and gradient strength. Here, we employ dissipative particle dynamics to describe the self-assembly of gradient copolymer melts with strong, intermediate, and weak gradient strength and compare their phase behavior to that of corresponding diblock copolymers. Gradient melts behave similarly when copolymers with a strong gradient are considered. Decreasing the gradient strength leads to the widening of the gyroid phase window, at the expense of cylindrical domains, and a remarkable extension of the lamellar phase. Finally, we show that weak gradient strength enhances chain packing in gyroid structures much more than in lamellar and cylindrical morphologies. Importantly, this work also provides a link between gradient copolymers morphology and parameters such as chemical incompatibility, chain length and monomer sequence as support for the rational design of these nanomaterials.
设计和制备具有特定性能的功能纳米材料需要精确控制其微观结构。一个典型的例子是双嵌段共聚物的自组装，它能生成由三个参数控制的高度有序结构：嵌段之间的化学不相容性、嵌段尺寸比和链长。聚合物合成的最新进展使得制备具有可控序列化学的梯度共聚物成为可能，从而提供了额外的参数来调整其组装。这些参数是多分散单体序列、嵌段尺寸分布和梯度强度。在这里，我们采用耗散粒子动力学来描述具有强、中、弱梯度强度的梯度共聚物熔体的自组装，并将它们的相行为与相应双嵌段共聚物的相行为进行比较。当考虑具有强梯度的共聚物时，梯度熔体的行为相似。降低梯度强度会导致螺旋状相窗口变宽，以圆柱形畴为代价，并且层状相显著扩展。最后，我们表明弱梯度强度比在层状和圆柱形形态中更能增强螺旋状结构中的链堆积。重要的是，这项工作还提供了梯度共聚物形态与化学不相容性、链长和单体序列等参数之间的联系，以支持这些纳米材料的合理设计。
