Área de Física de Procesos Irreversibles, División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Azcapotzalco, Av. San Pablo 180, 02200 Ciudad de México, Mexico.
Phys Chem Chem Phys. 2020 Aug 24;22(32):17913-17921. doi: 10.1039/d0cp03101a.
We present a model for mesoscopic molecular dynamics simulations of poly(N-isopropyl-acrylamide) (pNIPAM). The model uses a coarse-grained scheme based on the explicit-solvent Martini force field. The mapping of the polymer accounts for three beads per monomer. Similarly to the Martini water bead, the amide moieties of the polymer include an electric dipole. The model is tested by building polymer chains of different sizes and proved to accurately capture the thermal response of pNIPAM without including any temperature-dependent parameters. The critical temperature of the model is observed at (302.1 ± 1.1) K for a 35-mer and it keeps invariant when increasing the chain length. We deployed a series of replica-exchange molecular dynamics simulations that evidence the oligomer reaches thermodynamic equilibrium irrespective of the starting configuration. Finally, the model is applied to a membrane structure of pNIPAM where a good agreement with previous atomistic simulations is observed.
我们提出了一个用于聚 N-异丙基丙烯酰胺（pNIPAM）介观分子动力学模拟的模型。该模型使用基于显式溶剂 Martini 力场的粗粒化方案。聚合物的映射每个单体包含三个珠子。与 Martini 水分子珠类似，聚合物的酰胺部分包含一个电偶极子。通过构建不同大小的聚合物链对模型进行了测试，并证明在不包含任何依赖于温度的参数的情况下，该模型能够准确捕捉 pNIPAM 的热响应。该模型的临界温度在 35 -mer 时为 (302.1 ± 1.1) K，当链长增加时保持不变。我们进行了一系列 replica-exchange 分子动力学模拟，证明无论起始构型如何，低聚物都能达到热力学平衡。最后，该模型应用于 pNIPAM 的膜结构，观察到与以前的原子模拟有很好的一致性。
