Entropic Mixing of Ring/Linear Polymer Blends.
Entropic Mixing of Ring/Linear Polymer Blends.
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环/线性聚合物混合物的熵混合。
DOI：
10.1021/acspolymersau.2c00050
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发表时间：
2023-04-12
期刊：
影响因子：
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通讯作者：
O'Connor TC
中科院分区：
文献类型：
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作者：
Grest GS;Ge T;Plimpton SJ;Rubinstein M;O'Connor TC
非级联环聚合物的拓扑约束迫使它们形成比无约束理想环低得多的熵的紧凑的环状球状构象。环状聚合物的闭环结构也使它们能够在环/线性共混物中被线性聚合物穿线，导致具有较高熵的较不紧凑的环构象。这种构象熵增加促进了具有线性聚合物的混合环。在这里，使用珠弹簧链的分子动力学模拟，环/线性共混物被示出为比线性/线性共混物明显更易混溶，并且与线性/线性和环/环共混物相比，环/线性共混物存在熵混合，负χ。与小角中子散射类似，测量静态结构函数S（q），并将所得数据拟合到随机相位近似模型以确定χ。在两种组分相同的限度内，正如预期的那样，线性/线性和环/环混合物的χ = 0，而环/线性混合物的χ < 0。随着链刚度的增加，环/线性共混物的χ变得更负，随着缠结之间的单体数量而变化。环/线性共混物也显示出比环/环或线性/线性共混物更易混溶，并且对于两种组分之间更宽范围的增加的排斥力保持在单相。
The topological constraints of nonconcatenated ring polymers force them to form compact loopy globular conformations with much lower entropy than unconstrained ideal rings. The closed-loop structure of ring polymers also enables them to be threaded by linear polymers in ring/linear blends, resulting in less compact ring conformations with higher entropy. This conformational entropy increase promotes mixing rings with linear polymers. Here, using molecular dynamics simulations for bead-spring chains, ring/linear blends are shown to be significantly more miscible than linear/linear blends and that there is an entropic mixing, negative χ, for ring/linear blends compared to linear/linear and ring/ring blends. In analogy with small angle neutron scattering, the static structure function S(q) is measured, and the resulting data are fit to the random phase approximation model to determine χ. In the limit that the two components are the same, χ = 0 for the linear/linear and ring/ring blends as expected, while χ < 0 for the ring/linear blends. With increasing chain stiffness, χ for the ring/linear blends becomes more negative, varying reciprocally with the number of monomers between entanglements. Ring/linear blends are also shown to be more miscible than either ring/ring or linear/linear blends and stay in single phase for a wider range of increasing repulsion between the two components.