Smectic－Smectic Phase Segregation Occurring in Binary Mixtures of Long and Short Rigid-Rod Helical Polysilanes
Smectic－Smectic Phase Segregation Occurring in Binary Mixtures of Long and Short Rigid-Rod Helical Polysilanes
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近晶相－长短刚棒螺旋聚硅烷二元混合物中发生的近晶相偏析
DOI：
10.1021/acs.macromol.8b02462
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发表时间：
2019
期刊：
影响因子：
5.5
通讯作者：
Kento Okoshi
中科院分区：
文献类型：
--
作者：
Itsuki Kato;Katsuhiko Sunahara;Kento Okoshi
用小角X射线散射和原子力显微镜观察了分子量比为4.82、分子量分布窄的刚性棒状螺旋聚[正癸基（S）-2-甲基丁基硅烷]（PDMS）二元混合物的近晶-近晶相分离。相分离归因于熵效应，因为二元混合物中的均聚物仅分子量不同。从理论上预测了高压下不同长度的棒状颗粒混合物中近晶相的熵驱动偏析。具有更宽分子量分布的长和短PDMS的二元混合物，其不形成近晶相，没有显示出这样的分离，验证了分离的驱动力是通过近晶相形成获得的熵。具有窄分子量分布的长PDMS和具有宽分子量分布的短PDMS的二元混合物显示了每个组分的分离，表明短聚合物仅近晶相形成的熵增益超过了混合熵的损失。
Small-angle X-ray scattering and atomic force microscopy were used to observe smectic–smectic phase segregation in binary mixtures of rigid-rod-like helical poly[n-decyl-(S)-2-methylbutylsilane] (PDMS) polymers with molecular-weight ratios of 4.82 and narrow molecular-weight distributions. Phase segregation is attributed to entropic effects as the homopolymers in the binary mixture differ only in molecular weight. Entropy-driven segregation in smectic phases was theoretically predicted in mixtures of rodlike particles with different lengths under high pressure. Binary mixtures of long and short PDMS with broader molecular-weight distributions, which do not form smectic phases, showed no such segregation, verifying that the driving force for segregation is the entropy gained through smectic-phase formation. The binary mixture of a long PDMS with a narrow molecular-weight distribution and a short PDMS with a broad molecular-weight distribution showed segregation of each component, indicating that the entropy gain of short-polymer-only smectic phase formation surpasses the loss of mixing entropy.