Influence of TMAO as co-solvent on the gelation of silica-PNIPAm core-shell nanogels at intermediate volume fractions.,ChemPhysChem

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Influence of TMAO as co-solvent on the gelation of silica-PNIPAm core-shell nanogels at intermediate volume fractions.
ChemPhysChem ( IF 2.3 ) Pub Date : 2020-06-02 , DOI: 10.1002/cphc.202000114
Lara Frenzel _{1,

2} , Irina Lokteva _{1,

2} , Michael Koof _{1,

2} , Suresh Narayanan ₃ , Gerhard Grübel _{1,

2} , Felix Lehmkühler _{1,

2}

Affiliation

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：

TMAO 作为共溶剂对中间体积分数二氧化硅-PNIPAm 核壳纳米凝胶凝胶化的影响。

我们通过小角X射线散射和X射线光子相关光谱（XPCS）研究了分散在氧化三甲胺（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。）。当温度升高到 PNIPAm 的下临界溶液温度 33 °C 以上时，就会形成胶体凝胶，这可以通过小q时I ( q ) 的增加以及样品动力学各个数量级的减慢来确定。随着TMAO浓度的增加，凝胶化转变线性地转移至较低的温度。当TMAO浓度高于大约0.40mol/L（对应于TMAO和NIPAm基团的1:1比例）时，在所有温度下都发现塌陷的PNIPAm状态，而没有任何凝胶化转变。这表明，由于 TMAO 的存在，PNIPAm-水氢键的减少导致了塌陷的 PNIPAm 状态的稳定，并抑制了纳米凝胶的凝胶化。

更新日期：2020-06-02

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