Elucidating the impact of extreme nanoscale confinement on segmental and chain dynamics of unentangled poly(cis-1,4-isoprene)
Elucidating the impact of extreme nanoscale confinement on segmental and chain dynamics of unentangled poly(cis-1,4-isoprene)
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DOI：
10.1140/epje/i2019-11907-7
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发表时间：
2019-10
期刊：
影响因子：
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通讯作者：
T. Kinsey;E. Mapesa;T. Cosby;Youjun He;K. Hong;Yangyang Wang;C. Iacob;J. Sangoro
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文献类型：
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作者：
T. Kinsey;E. Mapesa;T. Cosby;Youjun He;K. Hong;Yangyang Wang;C. Iacob;J. Sangoro
摘要采用宽带介电光谱技术研究了低分子量聚顺式-1,4-异戊二烯（PI）在平均孔径为6.5 nm的单向二氧化硅纳米孔中的动力学。选择3个分子量的PI(3、7和10 kg/mol)，使其与聚合物旋转半径Rg的比值分别在3.4、2.3到1.9之间变化。研究发现，平均节段弛豫率保持块状，但随着分子量的增加（d /Rg减小），在较低的频率上出现了一个额外的过程。相反，对于接近d /Rg ~ 2的体系，对应于链动力学的端到端偶极子向量的平均弛豫速率略慢于体中，但对于具有最大分子量的聚合物，其弛豫速率比体中快。链弛豫的光谱形状分析表明，由于约束下的非理想链构象，10kg/mol PI在长度尺度上的动力学接近于theRgare，从而减少了链弛豫时间。了解极端几何约束下聚合物的这些快速链动力学对于设计在接近分子尺度的衬底中包含聚合物材料的纳米器件是必要的。图形抽象
AbstractBroadband 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 ofDto the polymer radius of gyration,Rg, 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 (decreasingD/Rg. 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 approachingD/Rg∼ 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 theRgare 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