Glasslike Transitions in Thin Polymer-Melt Films Due to Thickness Constraint
Glasslike Transitions in Thin Polymer-Melt Films Due to Thickness Constraint
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由于厚度限制，聚合物熔体薄膜中的玻璃状转变
DOI：
10.1023/a:1024444829848
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发表时间：
2003
影响因子：
3.2
通讯作者：
Takayuki Amiya
中科院分区：
文献类型：
--
作者：
S. Yamada;G. Nakamura;Yoko Hanada;Takayuki Amiya
利用表面力仪研究了星形和线形聚异戊二烯（PIP）熔体薄膜在高压下的剪切性能与滑动速度（剪切速率）的关系。结果与它们的体流变特性进行了对比；讨论了厚度约束对剪切性能的影响。至少在低剪切速率（频率）下，PIP熔体整体表现出类似牛顿的恒定粘度，这表明单个分子以横向滑动运动流动。然而，PIP熔体的薄膜表现出明显的剪切变薄行为的摩擦学特征，表明了在受限几何结构中的相关运动。剪切性能随厚度减小从体流变行为到薄膜摩擦学行为的变化反映了体系的物理状态及其转变；厚度限制导致了玻璃样的转变。还讨论了分子量和分子结构（星形或线性）对剪切性能的影响。
The shear properties of thin films of star and linear polyisoprene (PIP) melts under high pressure were investigated as a function of sliding velocity (shear rate) using the surface forces apparatus. The results were contrasted with their bulk rheological properties; effects of thickness constraint on the shear behavior were discussed. The melts of PIP in bulk exhibit Newtonian-like constant viscosity at least at low shear rates (frequencies), which suggests that individual molecules flow with lateral sliding motion. However, thin films of PIP melts show tribological features involving apparent shear-thinning behavior, indicative of the correlated motions in confined geometries. The shear-property change from bulk rheological behavior to thin-film tribological behavior along with the thickness decrease reflects the physical states and their transitions in the systems; the thickness constraint induces glasslike transitions. Effects of molecular weights and molecular architecture (star-branched or linear) on the shear properties are also discussed.