Surface tension of polystyrene blends: Theory and experiment
Surface tension of polystyrene blends: Theory and experiment
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聚苯乙烯共混物的表面张力：理论与实验
DOI：
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发表时间：
2009
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通讯作者：
L. Archer
中科院分区：
文献类型：
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作者：
Zhenyu Qian;V. Minnikanti;B. Sauer;G. T. Dee;W. Kampert;L. Archer
用改进的Wilhelmy法测定了线型-线型和星星/线型聚苯乙烯共混物的表面张力。我们的研究结果表明，对于这两种聚苯乙烯共混体系，表面张力组成的档案是凸的，表明一个强大的表面过剩的组件具有较低的表面能。星星/线性共混物显示出比它们的线性-线性对应物更凸的表面张力分布，表明支化组分相对于线性链的更强的表面偏析。作为理解星星聚合物增强表面偏析的物理起源的第一步，自洽场（SCF）晶格模拟（不可压缩和可压缩模型）和Cahn-Hilliard理论被用来预测表面张力组成的配置文件。从晶格模拟的结果表明，高度凸的表面张力分布观察到的星星/线性共混物系统是唯一可能的，如果一个架构依赖的，Flory相互作用参数（x = 0.004）是假设。这一结论是不一致的结果，从散装差示扫描量热法（DSC）的测量，这表明尖锐的玻璃化转变在这两个星星/线性和线性/线性均聚物共混物和一个简单的线性关系的散装玻璃化转变温度和共混物组合物。为了实现Cahn-Hilliard理论，首先测量共混物中每种纯组分的压力-体积-温度（PVT）数据，并将数据用作理论的输入。与实验数据相一致，Cahn-Hilliard理论预测在很宽的组成范围内，线性宿主中的星星分子的表面过剩较大。值得注意的是，这一结果是假设线性和星星成分之间的相互作用参数接近中性，这表明恒星表面的富集并不是大体积中复杂相行为的结果。
Surface tension of linear-linear and star/linear polystyrene blends were measured using a modified Wilhelmy method. Our results show that for both polystyrene blend systems, the surface tension-composition profile is convex, indicating a strong surface excess of the component with lower surface energy. Star/linear blends display more convex surface tension profiles than their linear―linear counterparts, indicative of stronger surface segregation of the branched-component relative to linear chains. As a first step toward understanding the physical origin of enhanced-surface segregation of star polymers, self-consistent field (SCF) lattice simulations (both incompressible and compressible models) and Cahn-Hilliard theory were used to predict surface tension-composition profiles. Results from the lattice simulations indicate that the highly convex surface tension profiles observed in the star/linear blend systems are only possible if an architecture-dependent, Flory interaction parameter ( x = 0.004) is assumed. This conclusion is inconsistent with results from bulk differential scanning calorimetry (DSC) measurements, which indicate sharp glass transitions in both the star/linear and linear/linear homopolymer blends and a simple linear relationship between the bulk glass transition temperature and blend composition. To implement the Cahn-Hilliard theory, pressure-volume-temperature (PVT) data for each of the pure components in the blends were first measured and the data used as input for the theory. Consistent with the experimental data, Cahn-Hilliard theory predicts a larger surface excess of star molecules in linear hosts over a wide composition range. Significantly, this result is obtained assuming a nearly neutral interaction parameter between the linear and star components, indicating that the surface enrichment of the stars is not a consequence of complex phase behavior in the bulk.