Monte Carlo simulations of coarse-grained polyethylene (PE) models were used to compare structural and dynamic properties of polymer chains confined at the nanoscale with different free surface geometries i.e. nanofilm, nanofiber and nanoparticle. All polymer nanostructures, which contain 95 chains of C₁₀₀H₂₀₂ were generated by serial reduction of the periodic boundary conditions. For all these nanostructures, the density profiles are hyperbolic, with end bead segregation at the surface. Bulk densities, sizes (thickness/radius) and the interfacial widths are lower, larger and broader for nanofilm, nanofiber and nanoparticle, respectively. The local environment of bond orientation is isotropic in the middle of these nanostructures, but becomes anisotropic near the surfaces. Chain orientation at the surface is also observed and the degree of anisotropy at the whole chain is nanofilm > nanofiber > nanoparticle. Surface energies are calculated directly from the on-lattice energetics and their magnitudes are: nanofilm < nanofiber < nanoparticle. The mobilities of polymers in the nanostructures at the level of bond and chain scales are greater for nanofilm > nanofiber > nanoparticle along the direction of periodic boundaries but this order is reversed for the diffusion along the direction normal to the free surfaces.

中文翻译：

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具有不同自由表面几何形状的聚乙烯纳米结构的结构和动力学：纳米膜，纳米纤维和纳米颗粒

粗粒聚乙烯（PE）模型的蒙特卡洛模拟用于比较局限在具有不同自由表面几何形状（即纳米薄膜，纳米纤维和纳米粒子）的纳米尺度上的聚合物链的结构和动态特性。所有包含95个C ₁₀₀ H ₂₀₂链的聚合物纳米结构是通过周期性边界条件的序列减少生成的。对于所有这些纳米结构，密度分布都是双曲线的，在表面存在端珠偏析。纳米膜，纳米纤维和纳米颗粒的堆积密度，尺寸（厚度/半径）和界面宽度分别较低，较大和较宽。键取向的局部环境在这些纳米结构的中间是各向同性的，但是在表面附近变成各向异性的。还观察到表面上的链取向，并且整个链的各向异性程度为纳米膜>纳米纤维>纳米颗粒。表面能直接从晶格上的高能学计算，其大小为：纳米膜<纳米纤维<纳米颗粒。