Stabilizing effect of TMAO on globular PNIPAM states: preferential attraction induces preferential hydration.
Stabilizing effect of TMAO on globular PNIPAM states: preferential attraction induces preferential hydration.
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TMAO 对球状 PNIPAM 态的稳定作用：优先吸引诱导优先水合
DOI：
10.1039/c6cp05991k
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
et int. G. Grübel
中科院分区：
文献类型：
--
作者：
M. A. Schroer;J. Michalowsky;et int. G. Grübel
用动态光散射(DLS)和全原子分子动力学(MD)模拟研究了有机共溶物三甲胺N氧化物(TMAO)对聚N-异丙基丙烯酰胺(PNIPAM)微凝胶粒子体积相变的影响。DLS测量揭示了TMAO诱导的PNIPAM微凝胶粒子从盘状到球状的连续收缩过程。用唯象Flory-Rehner理论对DLS数据进行分析，验证了TMAO存在时粒子球态的稳定性。互补的原子MD模拟突出了TMAO分子在PNIPAM链周围的显著积累。我们观察到TMAO和PNIPAM的球状状态之间存在显著的优先吸引力，与纯水溶液相比，球状状态的PNIPAM还被更多的水合水分子稳定。还对加入共溶质尿素的PNIPAM悬浮液进行了进一步的DLS测量。与TMAO实验结果相比，观察到的差异支持所提出的机理。
We study the effect of the organic co-solute trimethylamine N-oxide (TMAO) on the volume phase transition of microgel particles made from poly(N-isopropylacrylamide) (PNIPAM) using dynamic light scattering (DLS) and all-atom molecular dynamics (MD) simulations. The DLS measurements reveal a continuous TMAO-induced shrinking process from a coil to a globular state of PNIPAM microgel particles. Analyzing the DLS data by the phenomenological Flory–Rehner theory verifies the stabilization of the globular state of the particles in the presence of TMAO. Complementary atomistic MD simulations highlight a pronounced accumulation of TMAO molecules around PNIPAM chains. We observe a significant preferential attraction between TMAO and the globular state of PNIPAM, which is additionally stabilized by a larger number of hydrating water molecules compared to pure aqueous solutions. Further DLS measurements were also conducted on PNIPAM suspensions with the co-solute urea added. The observed differences compared with the results obtained for TMAO support the proposed mechanism.