Maltseva Daria, Zablotskiy Sergey, Martemyanova Julia, Ivanov Viktor, Shakirov Timur, Paul Wolfgang
Faculty of Physics, Lomonosov Moscow State University, Moscow 119991, Russia.
Institut für Physik, Martin-Luther-Universität, 06099 Halle(Saale), Germany.
Polymers (Basel). 2019 Apr 30;11(5):757. doi: 10.3390/polym11050757.
The combination of flexibility and semiflexibility in a single molecule is a powerful design principle both in nature and in materials science. We present results on the conformational behavior of a single multiblock-copolymer chain, consisting of equal amounts of Flexible (F) and Semiflexible (S) blocks with different affinity to an implicit solvent. We consider a manifold of macrostates defined by two terms in the total energy: intermonomer interaction energy and stiffness energy. To obtain diagrams of states (pseudo-phase diagrams), we performed flat-histogram Monte Carlo simulations using the Stochastic Approximation Monte Carlo algorithm (SAMC). We have accumulated two-Dimensional Density of States (2D DoS) functions (defined on the 2D manifold of macrostates) for a SF-multiblock-copolymer chain of length N = 64 with block lengths = 4, 8, 16, and 32 in two different selective solvents. In an analysis of the canonical ensemble, we calculated the heat capacity and determined its maxima and the most probable morphologies in different regions of the state diagrams. These are rich in various, non-trivial morphologies, which are formed without any specific interactions, and depend on the block length and the type of solvent selectivity (preferring S or F blocks, respectively). We compared the diagrams with those for the non-selective solvent and reveal essential changes in some cases. Additionally, we implemented microcanonical analysis in the "conformational" microcanonical ( N V U , where is the potential energy) and the true microcanonical ( N V E , where is the total energy) ensembles with the aim to reveal and classify pseudo-phase transitions, occurring under the change of temperature.
单个分子中灵活性与半灵活性的结合，在自然界和材料科学中都是一种强大的设计原则。我们展示了由等量的柔性（F）和半柔性（S）嵌段组成的单条多嵌段共聚物链的构象行为结果，这些嵌段对隐式溶剂具有不同的亲和力。我们考虑由总能量中的两个项定义的多种宏观状态：单体间相互作用能和刚度能。为了获得状态图（伪相图），我们使用随机近似蒙特卡罗算法（SAMC）进行了平直方图蒙特卡罗模拟。我们已经在两种不同的选择性溶剂中，针对长度N = 64、嵌段长度分别为4、8、16和32的SF - 多嵌段共聚物链，积累了二维态密度（2D DoS）函数（定义在宏观状态的二维流形上）。在正则系综分析中，我们计算了热容，并确定了其最大值以及状态图不同区域中最可能的形态。这些形态丰富多样且非平凡，它们在没有任何特定相互作用的情况下形成，并取决于嵌段长度和溶剂选择性类型（分别偏好S或F嵌段）。我们将这些图与非选择性溶剂的图进行了比较，并揭示了某些情况下的本质变化。此外，我们在“构象”微正则（N V U，其中U是势能）和真正的微正则（N V E，其中E是总能量）系综中进行了微正则分析，目的是揭示和分类在温度变化下发生的伪相变。
