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The phase diagram of colloidal silica-PNIPAm core-shell nanogels.
Soft Matter ( IF 2.9 ) Pub Date : 2019-11-25 , DOI: 10.1039/c9sm01884k Lara Frenzel 1 , Felix Lehmkühler , Michael Koof , Irina Lokteva , Gerhard Grübel
Soft Matter ( IF 2.9 ) Pub Date : 2019-11-25 , DOI: 10.1039/c9sm01884k Lara Frenzel 1 , Felix Lehmkühler , Michael Koof , Irina Lokteva , Gerhard Grübel
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We study the structure and dynamics of aqueous dispersions of densely packed core–shell nanoparticles composed of a silica core and a poly(N-isoproylacrylamide) (PNIPAm) shell as a function of temperature and concentration. With small angle X-ray scattering (SAXS) and X-ray photon correlation spectroscopy (XPCS) we shed light on the structural and dynamical changes of the thermo-responsive colloidal nanogel during its volume phase transition at a lower critical solution temperature (LCST) of 32 °C. A transition of the dynamics and its distinct dependency on the particle number concentration could be determined by analysing the intensity autocorrelation function while the structural transition remains concentration independent. We found the dynamics of a jammed system beyond a critical concentration. In addition, by variation of the PNIPAm shell size we tuned both the effective volume fraction and the underlying nature of the dynamics in the system. With our results we can present a full phase diagram of a PNIPAm core–shell system that spans from diluted suspensions, where the system behaves like a liquid, to an effective volume fraction of more than ninety percent where after exceeding a critical concentration the system undergoes a temperature-induced transition from a liquid towards a colloidal gel.
中文翻译：
胶体二氧化硅-PNIPAm核-壳纳米凝胶的相图。
我们研究了由二氧化硅核和聚（N（异丙基丙烯酰胺）（PNIPAm）壳随温度和浓度的变化而变化。利用小角度X射线散射（SAXS）和X射线光子相关光谱（XPCS），我们可以了解热响应性胶体纳米凝胶在较低临界溶液温度（LCST）的体积相变过程中的结构和动力学变化。的32°C。动力学的转变及其对颗粒数浓度的明显依赖性可以通过分析强度自相关函数来确定，而结构转变仍与浓度无关。我们发现卡纸系统的动态超出了临界浓度。另外，通过改变PNIPAm壳的大小，我们调整了系统中动力学的有效体积分数和基本特性。
更新日期：2019-11-25
中文翻译：
胶体二氧化硅-PNIPAm核-壳纳米凝胶的相图。
我们研究了由二氧化硅核和聚（N（异丙基丙烯酰胺）（PNIPAm）壳随温度和浓度的变化而变化。利用小角度X射线散射（SAXS）和X射线光子相关光谱（XPCS），我们可以了解热响应性胶体纳米凝胶在较低临界溶液温度（LCST）的体积相变过程中的结构和动力学变化。的32°C。动力学的转变及其对颗粒数浓度的明显依赖性可以通过分析强度自相关函数来确定，而结构转变仍与浓度无关。我们发现卡纸系统的动态超出了临界浓度。另外，通过改变PNIPAm壳的大小，我们调整了系统中动力学的有效体积分数和基本特性。
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