Studies on the behavior of nanoconfined homopolymers with cyclic chain architecture.
Studies on the behavior of nanoconfined homopolymers with cyclic chain architecture.
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DOI：
10.1063/1.1992474
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发表时间：
2005-08
期刊：
影响因子：
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通讯作者：
Johnny R. Maury-Evertsz;G. López
中科院分区：
文献类型：
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作者：
Johnny R. Maury-Evertsz;G. López
我们进行了Monte Carlo模拟，研究了在几种约束条件下，环状结构对均聚物链行为的影响。环的崩溃在两个阶段，线圈到球和liquidlike-to-solidlike过渡，观察到即使在极端的限制。这两个转变观察到在较低的温度下比相同长度的线性链，2%-5%低的无约束系统，和10%-15%低的壁间距低于三个键长由于限制的效果。当板块分离接近二维制度，线圈到球的转变转移到较低的温度。当链长增加时，观察到相反的趋势。在坍缩状态下，相同长度的线性和环状分子的平均尺寸和构象相似，与限制无关。在接近线团到球转变的温度下，无限制线性链的回转半径[R（g）（2）]（线性）变得大于环状链的回转半径[R（g）（2）]（环状），并且这种差异随着限制而显著增加。该区域的回转半径比[R（g）（2）]（线性）/[R（g）（2）]（循环）迅速减小。下降更明显，并发生在较低的温度下的狭缝宽度限制。在较高的温度下，在线圈状态下，回转比的半径变得几乎恒定的一个给定的分离，并从0.56为无约束系统的0.47时，链完全限制在墙壁之间。这种减少是由于更高的线性链的平均尺寸增加与限制相比，环状链，由于建筑的限制。
We have performed Monte Carlo simulations to study the effect of cyclic architecture on the behavior of homopolymer chains under several conditions of confinement. The collapse of the rings in two stages, a coil-to-globule and a liquidlike-to-solidlike transition, was observed even at extreme confinement. Both transitions were observed at lower temperatures than for linear chains of the same length, 2%-5% lower for unconfined systems, and 10%-15% lower for wall separations below three bond lengths due to the effect of confinement. When the plates separation approached the two-dimensional regime, the coil-to-globule transition shifted to lower temperatures. The inverse trend was observed when the chain length was increased. In the collapsed state, the average size and conformations of linear and cyclic molecules of same length were similar independently of confinement. At temperatures near the coil-to-globule transition, the radius of gyration of unconfined linear chains, [R(g)(2)](linear), became larger than for the cyclic chains, [R(g)(2)](cyclic), and this difference increased considerably with confinement. The radius of gyration ratio [R(g)(2)](linear)/[R(g)(2)](cyclic) in this region decreased rapidly. The decrease was more pronounced and occurred at lower temperatures for slit width confinements. At higher temperatures, in the coil state, the radius of gyration ratio became nearly constant for a given separation, and varied from 0.56 for unconfined systems to 0.47 when the chain was completely confined between the walls. This reduction was attributed to the higher increase in the average size of linear chains with confinement when compared with cyclic chains, due to architectural restrictions.