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arXiv 1401.7252cond-mat.stat-mechcond-mat.dis-nncond-mat.mtrl-sci
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动态停滞:玻璃化转变和凝胶化转变的相互作用

Dynamical arrest: interplay of the glass and of the gel transitions

Nagi Khalil, Antonio Coniglio, Antonio de Candia, Annalisa Fierro, Massimo Pica Ciamarra

摘要:

聚合物悬浮液的结构停滞可能由交联剂浓度的增加驱动,其驱动凝胶转变,以及由聚合物密度的增加驱动,其诱导玻璃化转变。这些动态连续(凝胶)和不连续(玻璃)转变可能会干扰,因为玻璃化转变可能发生在凝胶相,凝胶转变可能会在具有玻璃状特征的聚合物悬浮液中诱导。在这里,我们研究这些过渡的相互作用,通过调查事件驱动的分子动力学模拟的松弛动力学的聚合物悬浮液作为交联剂浓度和单体体积分数的函数。我们表明,凝胶相内的缓慢动态的特点是由一个长的子扩散制度,这是由于拥挤以及存在的一个passiating集群。在这个制度中,结构逮捕的过渡被发现发生沿凝胶或沿玻璃线,这取决于长度尺度的动态探测。在两条线相交的地方,没有明显的高阶动力学奇异性的迹象。典型的$A_{3}$奇异性的对数行为出现在凝胶相内沿玻璃化转变线。这些发现似乎与模式耦合理论的结果为$F_{13}$示意模型。

英文摘要:

The structural arrest of a polymeric suspension might be driven by an increase of the cross--linker concentration, that drives the gel transition, as well as by an increase of the polymer density, that induces a glass transition. These dynamical continuous (gel) and discontinuous (glass) transitions might interfere, since the glass transition might occur within the gel phase, and the gel transition might be induced in a polymer suspension with glassy features. Here we study the interplay of these transitions by investigating via event--driven molecular dynamics simulation the relaxation dynamics of a polymeric suspension as a function of the cross--linker concentration and the monomer volume fraction. We show that the slow dynamics within the gel phase is characterized by a long sub-diffusive regime, which is due both to the crowding as well as to the presence of a percolating cluster. In this regime, the transition of structural arrest is found to occur either along the gel or along the glass line, depending on the length scale at which the dynamics is probed. Where the two line meet there is no apparent sign of higher order dynamical singularity. Logarithmic behavior typical of $A_{3}$ singularity appear inside the gel phase along the glass transition line. These findings seem to be related to the results of the mode coupling theory for the $F_{13}$ schematic model.

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