The behavior of dense mixtures of two topologically different diblock copolymer (CP) chains, viz., linear (L)-CP and ring (R)-CP of the same molecular weight, which form lamellae is studied under confinement by two nonselective substrates. The effect of varying interaction strength between L-CP and R-CP from purely repulsive (demixed state) to weakly attractive (mixed state) on the morphology, domain size, chain conformations, and distribution of chains in the film is investigated. In the demixed state, collective structure factor S(q) shows a split of the predominant peak indicating the presence of two dominant length scales, while there is only one predominant peak in the mixed state, and hence a lamellar structure with single domain size. We show that the peak position q* of S(q) can be varied with the L/R interaction strength and thus allows one to control domain size by tuning L/R interaction strength without altering the chain size. We further characterize the chain size and illustrate that this domain size variation is a consequence of the variation in the size of L-CPs. Furthermore, results on the average instantaneous shape of R/L-CP reveal that their shapes are very different both in bulk and near the substrate, and R-CP assumes an oblate shape near the substrate. This shape/size difference leads to the segregation of R-CPs near the polymer–substrate interface and hence a relatively higher density of R-CPs at the interface.

中文翻译：

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封闭条件下的环状和线性共聚物共混物

在两个非选择性底物的限制下研究了两种拓扑不同的二嵌段共聚物（CP）链，即相同分子量的线性（L）-CP和相同分子量的环（R）-CP的致密混合物的行为。研究了L-CP和R-CP之间的相互作用强度从纯斥斥（脱附态）到弱吸引（混合态）的变化对膜的形态，畴尺寸，链构象和链分布的影响。在混合状态下，集合结构因子S（q）显示主要峰的分裂，表明存在两个主要长度尺度，而在混合状态下仅存在一个主要峰，因此具有单畴尺寸的层状结构。我们显示出峰值位置S（q）的q *可以随L / R相互作用强度而变化，因此可以通过调节L / R相互作用强度来控制域大小，而不改变链的大小。我们进一步表征链的大小，并说明此域大小的变化是L-CPs大小变化的结果。此外，R / L-CP的平均瞬时形状的结果表明，它们的形状无论在体积上还是在基材附近都非常不同，并且R-CP在基材附近呈扁圆形。这种形状/尺寸差异导致R-CP靠近聚合物-基材界面的偏析，因此导致界面上R-CP的密度相对较高。