Coil-Globule Collapse of Polystyrene Chains in Tetrahydrofuran-Water Mixtures.
Coil-Globule Collapse of Polystyrene Chains in Tetrahydrofuran-Water Mixtures.
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四氢呋喃-水混合物中聚苯乙烯链的线圈球体塌陷
DOI：
10.1021/acs.jpcb.7b10603
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
A. Nikoubashman
中科院分区：
文献类型：
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作者：
T.I. Morozova;A. Nikoubashman
我们用统一的原子模型进行分子动力学模拟，研究了溶液中单个高分子链的卷曲态和球状态。具体地说，我们表征的无规聚苯乙烯链与N = 20 - 150单体在四氢呋喃-水混合物在不同的混合比例的结构特性。我们发现，疏水性聚合物形成相当开放的线圈时，水的摩尔分数，XW，大致低于0.25，而链崩溃成小球时，XW = 0.75。我们证实了理论上预期的比例定律的回转半径，Rg，在这些制度，即，Rg <$N3/5和Rg <$N1/3分别用于良好和不良溶剂条件。对于XW = 0.75的不良溶剂条件，我们发现相当大的一部分残留的四氢呋喃被困在塌陷的聚合物链内，过量位于球表面，作为疏水聚苯乙烯和周围的富水混合物之间的保护层。这些发现对纳米颗粒制造技术具有重要意义，其中利用溶剂交换来驱动聚合物聚集，因为残留溶剂可以显着影响沉淀的纳米颗粒的物理性质。
We study the coil and globule states of a single polymer chain in solution by performing molecular dynamics simulations with a united atom model. Specifically, we characterize the structural properties of atactic polystyrene chains withN= 20–150 monomers in tetrahydrofuran–water mixtures at varying mixing ratios. We find that the hydrophobic polymers form rather open coils when the mole fraction of water,XW, is roughly below 0.25, whereas the chains collapse into globules whenXW≳ 0.75. We confirm the theoretically expected scaling laws for the radius of gyration,Rg, in these regimes, i.e.,Rg∝N3/5andRg∝N1/3for good and poor solvent conditions, respectively. For poor solvent conditions withXW= 0.75, we find a sizable fraction of residual tetrahydrofuran trapped inside the collapsed polymer chains with an excess amount located at the globule surface, acting as a protective layer between the hydrophobic polystyrene and the surrounding water-rich mixture. These findings have important implications for nanoparticle fabrication techniques where solvent exchange is exploited to drive polymer aggregation, since residual solvent can significantly influence the physical properties of the precipitated nanoparticles.