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Effect of pH and Molecular Length on the Structure and Dynamics of Linear and Short-Chain Branched Poly(ethylene imine) in Dilute Solution: Scaling Laws from Detailed Molecular Dynamics Simulations.
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-06-11 , DOI: 10.1021/acs.jpcb.0c04135 Dimitris G Mintis 1 , Terpsichori S Alexiou 1 , Vlasis G Mavrantzas 1, 2
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-06-11 , DOI: 10.1021/acs.jpcb.0c04135 Dimitris G Mintis 1 , Terpsichori S Alexiou 1 , Vlasis G Mavrantzas 1, 2
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Atomistic molecular dynamics (MD) simulations are carried out to examine the effect of molecular weight Mw (= 0.6, 0.86, 1.12, and 2.15 kDa) and pH (or equivalently, degree of ionization, α+ = 0, 50, and 100%) on the structure, state of hydration, and dynamics of linear and branched poly(ethylene imine) (PEI) chains in infinitely dilute salt-free aqueous solutions. It is found that the degree of ionization is the key factor determining the type of molecular conformation adopted by PEI, regardless of molecular architecture and chain length, resulting in a stable trans conformation for fully ionized solutions and in a stable gauche+/gauche– state for neutral or alternate ionized ones; in the latter case, a strong electrolyte behavior is verified for both linear and branched PEI. Linear PEI is observed to be significantly stiffer than branched PEI of the same molecular weight at 100% degree of ionization, but the effect subsides as the degree of ionization decreases. Also, linear PEI diffuses markedly slower than branched PEI of the same Mw. From the MD results, scaling exponents are deduced and reported for the conformation, solvent-accessible surface area, and dynamics of the two different PEI structures with Mw.
中文翻译：
pH和分子长度对线性和短链支化聚乙烯亚胺在稀溶液中的结构和动力学的影响：详细分子动力学模拟的尺度定律。
进行原子分子动力学（MD）模拟以检查分子量M w（= 0.6、0.86、1.12和2.15 kDa）和pH（或等效地电离度，α + = 0、50和100）的影响％）在无限稀释的无盐水溶液中的线性和支化聚亚乙基亚胺（PEI）链的结构，水合状态以及动力学。研究发现，电离度是决定PEI采用的分子构象类型的关键因素，而与分子结构和链长无关，从而为完全电离的溶液产生稳定的反式构象，并产生稳定的gauche + / gauche –中性或交替离子化状态；在后一种情况下，线性和支链PEI均证实了强电解质行为。在100％的电离度下，线性PEI比相同分子量的支链PEI明显更硬，但随着电离度的降低，这种作用减弱。此外，线性PEI明显慢于相同的支链PEI扩散中号瓦特。从MD结果，标度指数推导和报道的构象，溶剂可及表面积，并且与两个不同PEI结构的动力学中号瓦特。
更新日期：2020-07-16
中文翻译：
pH和分子长度对线性和短链支化聚乙烯亚胺在稀溶液中的结构和动力学的影响：详细分子动力学模拟的尺度定律。
进行原子分子动力学（MD）模拟以检查分子量M w（= 0.6、0.86、1.12和2.15 kDa）和pH（或等效地电离度，α + = 0、50和100）的影响％）在无限稀释的无盐水溶液中的线性和支化聚亚乙基亚胺（PEI）链的结构，水合状态以及动力学。研究发现，电离度是决定PEI采用的分子构象类型的关键因素，而与分子结构和链长无关，从而为完全电离的溶液产生稳定的反式构象，并产生稳定的gauche + / gauche –中性或交替离子化状态；在后一种情况下，线性和支链PEI均证实了强电解质行为。在100％的电离度下，线性PEI比相同分子量的支链PEI明显更硬，但随着电离度的降低，这种作用减弱。此外，线性PEI明显慢于相同的支链PEI扩散中号瓦特。从MD结果，标度指数推导和报道的构象，溶剂可及表面积，并且与两个不同PEI结构的动力学中号瓦特。
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