聚乙二醇溶液中微观结构对polymer链动力学的影响
Effect of microstructure on polymer chain dynamics in polyethylene glycol solutions
摘要：
用宏观尺度的振荡流变学和微观尺度的荧光探针扩散研究了聚乙二醇（PEG）水溶液的微观结构和相互作用对链段动力学的影响。光漂白后PEG溶液荧光恢复（FRAP）曲线具有随PEG浓度增加的不动分数，对于PEG体积分数（c）> 0.2，表明结构化。PEG溶液微尺度扩散系数遵循劳斯标度D {\ alpha} c^（-0.54），c < 0.8，类似于良好溶剂中的未缠结中性聚合物。在PEG基质中添加纳米粘土膨润土（B）使探针扩散减慢3-7倍，具有非均匀动力学。在PEG基质中加入羧甲基纤维素（CMC），探针扩散是均匀的，扩散时间的增加微不足道。PEG、PEG+B和PEG + CMC溶液的宏观尺度储存模量缩放为粘性流体样，随后是短的弹性平台。在弹性平台之外，缩放是浓度依赖性幂律，大于0.1<c<0.2 PEG溶液的0.5的Rouse缩放。我们确定了PEG分子间相互作用的时间尺度τ_b，使得当ω>τ_b^（-1）时，Rouse标度恢复。向PEG中加入CMC也可恢复Rouse结垢。此外，B给出的贡献，从聚合物基体和网络的B粒子，导致偏离纯劳斯行为。静态微观结构研究表明，随着PEG基质中粘土颗粒浓度的增加，粘土颗粒之间的耗尽相互作用导致了粘土颗粒的聚集，从而导致了储能模量与c的非单调浓度依赖关系。
英文摘要：
Effect of microstructures and interactions on segmental dynamics in polyethylene glycol (PEG) solution in water is probed with macro-scale oscillatory rheology and micro-scale diffusion of a fluorescent probe. PEG solution fluorescence recovery after photobleaching (FRAP) curves have immobile fractions which increase with PEG concentration, for PEG volume fraction (c) > 0.2, indicating structuring. PEG solution micro-scale diffusion coefficients follow Rouse scaling D {\ alpha} c^(-0.54) for c < 0.8, resembling unentangled neutral polymers in good solvent. Addition of nanoclay bentonite (B) in PEG matrix slows down probe diffusion 3-7 times, with heterogeneous dynamics. With addition of carboxymethyl cellulose (CMC) in PEG matrix, probe diffusion is homogeneous with negligibly small enhancement in diffusion time. The macroscale storage modulii for PEG, PEG+B, and PEG + CMC solutions scale as viscous fluid-like, followed by short elastic plateau. Beyond the elastic plateau, the scaling is a concentration-dependent power law greater than the Rouse scaling of 0.5 for 0.1<c<0.2 PEG solutions. We identify a time scale τ_b due to intermolecular interactions in PEG, such that for ω>τ_b^(-1) , Rouse scaling is recovered. Addition of CMC to PEG also restores Rouse scaling. Addition of B gives contributions from both polymer matrix and network of B particles, leading to departure from pure Rouse behaviour. Static microstructural studies reveal clay aggregation due to depletion interactions on increasing the concentration of clay particles in PEG matrix, which leads to a non-monotonic concentration dependence of storage modulus with c.
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