posted on 2024-01-09, 08:33authored byRuijun Zhao, Yingzhuo Liu, Zhe Ma
Flow-induced crystallization is a multistep process,
in which precursors
are often generated as a crucial ordering state intermediate between
the initial amorphous state and the ultimate crystallite. In this
work, the self-nucleation effect of isotactic polybutene-1 was employed
to obtain the ordering precursors and to study flow-induced crystallization
that started from both the self-nucleated precursors and the completely
relaxed amorphous phase. This could answer the long-standing question
whether the additional self-nucleated precursors behave as the flow-induced
ordering structures to facilitate crystallization or are erased back
to the completely relaxed melt under the action of flow. The results
showed that for quiescent crystallization, the self-nucleated precursors
effectively accelerated kinetics and exhibited a monotonously increasing
dependence with decreasing self-nucleation temperatures over a broad
range of 117–180 °C. Interestingly, with flow, the self-nucleated
precursors were able to accelerate crystallization significantly by
facilitating the initial step of generating local ordering precursors.
In addition, it was unexpected to find a type of unique precursor
through self-nucleation at 137 and 138 °C. Such self-nucleated
precursors remained unavailable for quiescent crystallization but
could be activated by flow, referred to as dormant self-nucleated
precursors in this work. To the best of our knowledge, the dormant
self-nucleated precursors, which have nonfunctionality under the quiescent
condition but can be visualized by flow, were reported for the first
time. Moreover, the flow-induced evolution of various self-nucleated
precursors was investigated by controlling the shearing duration.
It was found that the self-nucleated precursors can develop into oriented
nuclei, accelerating crystallization kinetics and increasing the crystallite
orientation.