Abstract.

Broadband dielectric spectroscopy is employed to probe dynamics in low molecular weight poly(cis-1,4-isoprene) (PI) confined in unidirectional silica nanopores with mean pore diameter, D, of 6.5 nm. Three molecular weights of PI (3, 7 and 10 kg/mol) were chosen such that the ratio of D to the polymer radius of gyration, R_g, is varied from 3.4, 2.3 to 1.9, respectively. It is found that the mean segmental relaxation rate remains bulk-like but an additional process arises at lower frequencies with increasing molecular weight (decreasing D/R_g. In contrast, the mean relaxation rates of the end-to-end dipole vector corresponding to chain dynamics are found to be slightly slower than that in the bulk for the systems approaching D/R_g ∼ 2, but faster than the bulk for the polymer with the largest molecular weight. The analysis of the spectral shapes of the chain relaxation suggests that the resulting dynamics of the 10kg/mol PI confined at length-scales close to that of the R_g are due to non-ideal chain conformations under confinement decreasing the chain relaxation times. The understanding of these faster chain dynamics of polymers under extreme geometrical confinement is necessary in designing nanodevices that contain polymeric materials within substrates approaching the molecular scale.

Graphical abstract

中文翻译：

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阐明了极端纳米级限制对未缠结的聚（顺式1,4-异戊二烯）的链段和链动力学的影响。

摘要。

宽带介电谱用于探测限制在平均孔径D为6.5 nm的单向二氧化硅纳米孔中的低分子量聚顺式-1,4-异戊二烯（PI）的动力学。选择三种分子量的PI（3、7和10kg / mol），使得D与聚合物回转半径R _g的比分别从3.4、2.3至1.9变化。发现平均节段弛豫速率保持为块状，但随着分子量的增加（D / R _g降低），在较低的频率下会出现一个附加过程。。相反，对于接近D / R _g〜2的系统，端到端偶极子向量对应于链动力学的平均弛豫率比整体中的慢一些，但比聚合物快。具有最大的分子量。对链弛豫的光谱形状的分析表明，所得的10kg / mol PI动力学仅限于接近R _g的长度尺度。是由于限制条件下的非理想链构象减少了链弛豫时间。在设计纳米器件时，必须了解在极端几何限制下聚合物的这些更快的链动力学，这些纳米器件在接近分子尺度的底物中包含聚合材料。

图形概要