Self-Diffusion of Associating Star-Shaped Polymers
Self-Diffusion of Associating Star-Shaped Polymers
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DOI：
10.1021/acs.macromol.6b00959
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发表时间：
2016-08-09
期刊：
影响因子：
5.5
通讯作者：
Olsen, Bradley D.
中科院分区：
文献类型：
--
作者：
Tang, Shengchang;Habicht, Axel;Olsen, Bradley D.
在瞬态聚合物网络中，缔合键的动力学对其弛豫和时间依赖性力学性能有着至关重要的影响。特别地，由可逆连接的解离和缔合平衡介导的聚合物的扩散运动可以影响材料的结构稳定性、动态机械性能和由聚合物链的恒定运动产生的宽范围的功能性。在这项工作中，强迫瑞利散射被用来测量三联吡啶末端官能化的四臂聚（乙二醇）聚合物的扩散瞬间互连的锌离子在有机溶剂中跨越广泛的长度和时间尺度。现象学的超扩散，其中的平方长度尺寸与时间的缩放具有大于1的幂律指数，被证明是由于链解离和扩散的相互作用，这些网络的内在特征。超扩散制度外，正常的菲克扩散恢复大，小的长度尺度。数据定量描述与先前开发的一个快速和一个缓慢扩散的物种，允许相互转换的两态模型。提取的扩散系数显示浓度依赖性缩放与粘性劳斯模型的良好协议。同样的聚合物，但只有三个关联臂通过相同的瞬态网络的扩散也进行了研究，表现出更快的链扩散系数相比，与四个关联臂的聚合物的情况下。这些实验结果定量地显示了在瞬态聚合物网络中，粘贴密度和价态对链扩散的影响。
The dynamics of associating bonds in transient polymer networks exerts a paramount influence on their relaxation and time dependent mechanical properties. In particular, diffusive motion of polymers mediated by the dissociation and association equilibrium of reversible junctions can affect the materials' structural stability, dynamic mechanical properties, and a broad spectrum of functionality that arises from the constant motion of polymer chains. In this work, forced Rayleigh scattering is used to measure the diffusion of terpyridine end-functionalized four-arm poly(ethylene glycol) polymers transiently interlinked by zinc ions in organic solvent across a wide range of length and time scales. Phenomenological superdiffusion, where the scaling of the squared length dimension vs time has a power-law exponent larger than one, is demonstrated as an intrinsic feature of these networks due to the interplay of chain dissociation and diffusion. Outside the superdiffusive regime, normal Fickian diffusion is recovered on both large and small length scales. The data are quantitatively described with a previously developed two-state model of one fast and one slow diffusing species that are allowed to interconvert. The extracted diffusivities show concentration-dependent scaling in good agreement with the sticky Rouse model. Diffusion of the same polymers but with only three associating arms through the same transient networks is also investigated, which exhibits faster chain diffusivities compared to the case of the polymers with four associating arms. These experimental results quantitatively show the effect of sticker density and valency on chain diffusion in transient polymer networks.