We study the structure and dynamics of poly(N‐isopropylacrylamide) (PNIPAm) core‐shell nanogels dispersed in aqueous trimethylamine N‐oxide (TMAO) solutions by means of small‐angle X‐ray scattering and X‐ray photon correlation spectroscopy (XPCS). Upon increasing the temperature above the lower critical solution temperature of PNIPAm at 33 °C, a colloidal gel is formed as identified by an increase of I(q) at small q as well as a slowing down of sample dynamics by various orders of magnitude. With increasing TMAO concentration the gelation transition shifts linearly to lower temperatures. Above a TMAO concentration of approximately 0.40 mol/L corresponding to a 1 : 1 ratio of TMAO and NIPAm groups, collapsed PNIPAm states are found for all temperatures without any gelation transition. This suggests that reduction of PNIPAm‐water hydrogen bonds due to the presence of TMAO results in a stabilisation of the collapsed PNIPAm state and suppresses gelation of the nanogel.

中文翻译：

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TMAO作为助溶剂对二氧化硅-PNIPAm核壳纳米凝胶在中等体积分数下凝胶化的影响。

我们通过小角X射线散射和X射线光子相关光谱法（XPCS）研究了分散在三甲胺N氧化物（TMAO）水溶液中的聚（N-异丙基丙烯酰胺）（PNIPAm）核壳纳米凝胶的结构和动力学）。当温度升高至高于PNIPAm的较低临界溶液温度（33°C）时，形成胶体凝胶，这可通过在小q时I（q）增大来确定。以及将样品动力学降低了多个数量级。随着TMAO浓度的增加，胶凝转变线性地转移到较低的温度。在高于约0.40 mol / L的TMAO浓度（对应于TMAO和NIPAm基团的1：1比例）之上，发现在所有温度下塌缩的PNIPAm状态而没有任何胶凝转变。这表明由于TMAO的存在而导致PNIPAm-水氢键的减少导致塌陷的PNIPAm状态的稳定并抑制了纳米凝胶的凝胶化。