Dynamics of Acrylamide Hydrogels, Polymers, and Monomers in Water Measured with Optical Heterodyne-Detected Optical Kerr Effect Spectroscopy
Dynamics of Acrylamide Hydrogels, Polymers, and Monomers in Water Measured with Optical Heterodyne-Detected Optical Kerr Effect Spectroscopy
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用光学外差检测光学克尔效应光谱测量水中丙烯酰胺水凝胶、聚合物和单体的动力学
DOI：
10.1021/acs.jpcb.2c08164
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Fayer, Michael D.
中科院分区：
文献类型：
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作者：
Van Wyck, Stephen J.;Fayer, Michael D.
利用光学外差探测光学克尔效应（OHD-OKE）光谱研究了丙烯酰胺单体（AAm）、聚丙烯酰胺（PAAm）和聚丙烯酰胺水凝胶（PAAm-HG）在水中的超快动力学。以前的超快红外（IR）测量的水动力学表明，在相同浓度的丙烯酰胺部分，AAm，PAAm，和PAAm-HG表现出相同的水动力学，这些动力学随浓度的增加而减慢。与IR测量相反，OHD-OKE实验测量水和丙烯酰胺物质的动力学，其发生在不同的时间尺度上。在这项研究中，所有丙烯酰胺体系的动力学随浓度的增加而减慢。我们发现，AAm表现出四指数衰减，其中最长的成分遵循Debye-Stokes-Einstein行为，除了最高浓度，40%（w/v）。低浓度的PAAm遵循一个单一的幂律衰减，而高浓度的PAAm和所有浓度的PAAm-HG衰减两个幂律。PAAm和PAAm-HG的最高浓度（25%和40%）表现出几乎相同的动力学。我们认为这一结果反映了类似程度的链-链相互作用。在低浓度下，PAAm显示非马尔可夫，单链动力学（单幂律），但PAAm显示纠缠链链相互作用在高浓度（两个幂律）。PAAm-HG在由交联引起的所有浓度下具有链-链相互作用。在高浓度下，PAAm的缠结动力学在误差内变得与交联PAAm-HG的缠结动力学相同。
The ultrafast dynamics of acrylamide monomers (AAm), polyacrylamide (PAAm), and polyacrylamide hydrogels (PAAm-HG) in water were studied using optical heterodyne-detected optical Kerr effect (OHD-OKE) spectroscopy. Previous ultrafast infrared (IR) measurements of the water dynamics showed that at the same concentration of the acrylamide moiety, AAm, PAAm, and PAAm-HG exhibited identical water dynamics and that these dynamics slowed with increasing concentration. In contrast to the IR measurements, OHD-OKE experiments measure the dynamics of both the water and the acrylamide species, which occur on different time scales. In this study, the dynamics of all the acrylamide systems slowed with increasing concentration. We found that AAm exhibits tetraexponential decays, the longest component of which followed Debye–Stokes–Einstein behavior except for the highest concentration, 40% (w/v). Low concentrations of PAAm followed a single power law decay, while high concentrations of PAAm and all concentrations of PAAm-HG decayed with two power laws. The highest concentrations, 25% and 40%, of PAAm and PAAm-HG showed nearly identical dynamics. We interpreted this result as reflecting a similar extent of chain–chain interactions. At low concentrations, PAAm displays non-Markovian, single-chain dynamics (single power law), but PAAm displays entangled chain–chain interactions at high concentrations (two power laws). PAAm-HG has chain–chain interactions at all concentrations that arise from the cross-linking. At high concentrations, the dynamics of the entangled of PAAm become identical within error as those of the cross-linked PAAm-HG.