Effect of Polymer Concentration on Structure and Dynamics of Short Poly(N,N-dimethylaminoethyl methacrylate) in aqueous solution: A Combined Experimental and Molecular Dynamics Study.
Effect of Polymer Concentration on Structure and Dynamics of Short Poly(N,N-dimethylaminoethyl methacrylate) in aqueous solution: A Combined Experimental and Molecular Dynamics Study.
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聚合物浓度对水溶液中短聚（N,N-二甲基氨基乙基甲基丙烯酸酯）结构和动力学的影响：实验和分子动力学相结合的研究。
DOI：
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发表时间：
2019
影响因子：
3.3
通讯作者：
V. Mavrantzas
中科院分区：
文献类型：
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作者：
Dimitris G Mintis;Marco Dompé;M. Kamperman;V. Mavrantzas
采用实验和分子动力学（MD）相结合的方法研究了聚合物浓度对聚甲基丙烯酸N，N-二甲氨基乙酯（PDMAEMA）无盐水溶液零剪切速率粘度η 0的影响.该研究在室温（T = 298 K）下进行，具有相对短的PDMAEMA链（每个链包含N = 20个单体或重复单元），电离度固定（α + = 100%）。对于MD模拟，首先进行几个分子力学力场的彻底验证，以评估其准确再现实验观察和建立的理论定律的能力。最后采用广义Amber力场结合RESP电荷拟合方法。三个特征浓度制度被认为是：稀释（从5重量%至10重量%），半稀释（从10重量%至20重量%），和浓缩（从20重量%至29重量%），后两个的特征在于聚合物浓度高于特征重叠浓度c_p*。通过计算PDMAEMA链的均方回转半径R_g的平方根、平均链端距R_ee的平方根、比值/、在低聚合物浓度下，由于排斥体积效应，PDMAEMA分子链呈现较硬的构象，并略有伸长（在本研究中考虑良溶剂）和聚合物链内的静电排斥。随着聚合物浓度增加到20重量%以上，PDMAEMA链采用更灵活的构象，因为排除体积效应抓住和聚合物链内的电荷排斥消退。总聚合物浓度对PDMAEMA链在溶液中的动力学的影响进行评估，通过计算链取向弛豫时间τ_c，质量扩散系数D的中心，和零剪切速率粘度η_0;后者也在这里进行了实验测量，发现是在良好的协议与MD预测。
A combined experimental and Molecular Dynamics (MD) study is performed to investigate the effect of polymer concentration on the zero-shear rate viscosity eta_0 of a salt-free aqueous solution of poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), a flexible thermo-responsive weak polyelectrolyte with a bulky 3-methyl-1,1-diphenylpentyl unit as a terminal group. The study is carried out at room temperature (T = 298 K) with relatively short PDMAEMA chains (each containing N = 20 monomers or repeat units) at fixed degree of ionization (α + = 100%). For the MD simulations, a thorough validation of several molecular mechanics force fields is first undertaken for assessing their capability to accurately reproduce experimental observations and established theoretical laws. The generalized Amber force field in combination with the RESP charge fitting method is eventually adopted. Three characteristic concentration regimes are considered: the dilute (from 5 wt % to 10 wt %), the semi-dilute (from 10 wt % to 20 wt %), and the concentrated (from 20 wt % to 29 wt %); the latter two are characterized by polymer concentrations higher than the characteristic overlap concentration c_p*. The structural behaviour of the PDMAEMA chains in the solution is assessed by calculating the square root of their mean square radius-of-gyration R_g, the square root of the average square chain end-to-end distance R_ee, the ratio / , and the persistence length L_p. It is observed that at low polymer concentrations PDMAEMA chains adopt a stiffer and slightly extended conformation due to excluded-volume effects (good solvent is considered in this study) and electrostatic repulsions within the polymer chains. As the polymer concentration increases above 20 wt %, PDMAEMA chains adopt more flexible conformations, since excluded-volume effects seize and charge repulsion within polymer chains subsides. The effect of total polymer concentration on PDMAEMA chain dynamics in the solution is assessed by calculating the chain orientational relaxation time tau_c, the center-of-mass diffusion coefficient D, and the zero-shear rate viscosity eta_0; the latter is also measured experimentally here and found to be in excellent agreement with the MD predictions.
影响因子：
5.5
作者：
Plamper, Felix A.;Ruppel, Markus;Mueller, Axel H. E.
通讯作者：
Mueller, Axel H. E.