Ultrafast nonexponential dynamics in a polymer glass forming liquid
Ultrafast nonexponential dynamics in a polymer glass forming liquid
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聚合物玻璃形成液体中的超快非指数动力学
DOI：
10.1063/1.466595
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发表时间：
1994
影响因子：
4.4
通讯作者：
M. Fayer
中科院分区：
文献类型：
--
作者：
A. Sengupta;M. Fayer
利用亚皮秒瞬态光栅光学克尔效应（TGOKE）测量，研究了聚甲基苯基硅氧烷（PMPS）熔体中苯基侧基在粘度/温度（η/T）范围内的取向动力学。对聚二甲基硅氧烷的测定也作了报道。在超快（数百）fs的振动动力学之后，苯基侧基取向动力学发生在2ps到几百ps的时间范围内。实验在25 ~ 143℃进行，η/T变化了40倍。尽管η/T变化很大，但在整个温度范围内，侧群动力学保持不变。熔体中PMPS和稀CCl4溶液中PMPS的动力学比较表明，链式相互作用影响熔体中苯基的动力学。这种动力学被描述为苯基在微环境中的局部取向弛豫，这种弛豫是由主链几何和侧基空间相互作用而不是由主链几何和侧基空间相互作用来定义的。
The orientational dynamics of phenyl side groups in poly(methylphenylsiloxane) (PMPS) melts are examined over a broad range of viscosity/temperature (η/T) using subpicosecond transient grating optical Kerr effect (TGOKE) measurements. Measurements on poly(dimethylsiloxane) are also reported. Following ultrafast (hundreds) of fs librational dynamics, the phenyl side group orientational dynamics occur over a range of times from 2 ps to a few hundred ps. The experiments were performed from 25 to 143 °C, resulting in η/T changing by a factor of 40. In spite of the large change in η/T, the side group dynamics remain unchanged throughout the entire temperature range. Comparison of the dynamics of PMPS in the melt and PMPS in dilute CCl4 solution shows that chain–chain interactions influence the phenyl side group dynamics in the melt. The dynamics are described as local orientational relaxation of phenyl groups in the microenvironments defined by the backbone geometry and side group steric interactions rather th...