Ali Samim, Prabhu Vivek M
Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA.
Gels. 2018 Jan 18;4(1):11. doi: 10.3390/gels4010011.
Complexation between anionic and cationic polyelectrolytes results in solid-like precipitates or liquid-like coacervate depending on the added salt in the aqueous medium. However, the boundary between these polymer-rich phases is quite broad and the associated changes in the polymer relaxation in the complexes across the transition regime are poorly understood. In this work, the relaxation dynamics of complexes across this transition is probed over a wide timescale by measuring viscoelastic spectra and zero-shear viscosities at varying temperatures and salt concentrations for two different salt types. We find that the complexes exhibit time-temperature superposition (TTS) at all salt concentrations, while the range of overlapped-frequencies for time-temperature-salt superposition (TTSS) strongly depends on the salt concentration () and gradually shifts to higher frequencies as is decreased. The sticky-Rouse model describes the relaxation behavior at all . However, collective relaxation of polyelectrolyte complexes gradually approaches a rubbery regime and eventually exhibits a gel-like response as is decreased and limits the validity of TTSS.
在水介质中，阴离子和阳离子聚电解质之间的络合作用会根据添加的盐形成固体状沉淀或液体状凝聚层。然而，这些富含聚合物的相之间的界限相当宽泛，并且在整个转变区域中，络合物中聚合物弛豫的相关变化还不太清楚。在这项工作中，通过测量两种不同盐类型在不同温度和盐浓度下的粘弹性光谱和零剪切粘度，在很宽的时间尺度上探究了络合物在这个转变过程中的弛豫动力学。我们发现，在所有盐浓度下，络合物都表现出时间-温度叠加（TTS），而时间-温度-盐叠加（TTSS）的重叠频率范围强烈依赖于盐浓度（），并且随着的降低逐渐向更高频率移动。粘性-劳斯模型描述了所有情况下的弛豫行为。然而，随着的降低，聚电解质络合物的集体弛豫逐渐接近橡胶态，最终表现出类似凝胶的响应，这限制了TTSS的有效性。
