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.

中文翻译：

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从线圈到球过渡的聚（N-异丙基丙烯酰胺）粗粒度模型。

我们提出了一个聚（N的介观分子动力学模拟的模型-异丙基-丙烯酰胺）（pNIPAM）。该模型使用基于显式溶剂马蒂尼力场的粗粒度方案。聚合物的映射说明每个单体三个小珠。类似于马提尼水珠，聚合物的酰胺部分包括电偶极子。该模型通过构建不同大小的聚合物链进行了测试，并被证明可以准确捕获pNIPAM的热响应，而无需包含任何与温度相关的参数。对于35个链节，模型的临界温度为（302.1±1.1）K，在增加链长时保持不变。我们部署了一系列的复制-交换分子动力学模拟，以证明无论起始构型如何，低聚物均达到热力学平衡。最后，