Krasnov Igor, Seydel Tilo, Müller Martin
Institut für Experimentelle und Angewandte Physik, Universität Kiel, D-24098 Kiel, Germany.
Institute of Materials Research, Helmholtz-Zentrum Geesthacht (HZG), D-21502 Geesthacht, Germany.
Phys Rev E Stat Nonlin Soft Matter Phys. 2015 Apr;91(4):042716. doi: 10.1103/PhysRevE.91.042716. Epub 2015 Apr 28.
Structural relaxations in humid silk fibers exposed to tensile stress have been reported to take place on a very wide range of time scales from a few milliseconds to several hours. The time-dependence of the measured tensile force following a quasi-instantaneously applied external strain on the fibers can be understood in terms of a fractional viscoelastic relaxation function introducing memory effects by which the mechanical state of a fiber depends on its tensile history. An analog fractional relaxation also gives rise to the subdiffusion observed on picosecond time scales, which governs the mobility of the amorphous polymer chains and adsorbed water on the molecular level. The reduction of the subdiffusive memory effect in stretched fibers compared to native fibers is consistent with the higher order of the polymers in the stretched state.
据报道，暴露于拉伸应力下的湿蚕丝纤维中的结构弛豫发生在从几毫秒到几小时的非常广泛的时间尺度上。在纤维上准瞬间施加外部应变后，测量到的拉伸力的时间依赖性可以通过引入记忆效应的分数粘弹性弛豫函数来理解，通过该函数，纤维的机械状态取决于其拉伸历史。类似的分数弛豫也导致了在皮秒时间尺度上观察到的亚扩散，这在分子水平上控制着无定形聚合物链和吸附水的流动性。与天然纤维相比，拉伸纤维中亚扩散记忆效应的降低与拉伸状态下聚合物的更高阶数一致。
