Contrast variation SANS measurement of shell monomer density profiles of smart core-shell microgels.
Contrast variation SANS measurement of shell monomer density profiles of smart core-shell microgels.
复制标题
DOI：
10.1039/c9sm02036e
复制
发表时间：
2020-01
期刊：
影响因子：
3.4
通讯作者：
M. Cors;Lars Wiehemeier;Oliver Wrede;A. Feoktystov;F. Cousin;T. Hellweg;J. Oberdisse
中科院分区：
文献类型：
--
作者：
M. Cors;Lars Wiehemeier;Oliver Wrede;A. Feoktystov;F. Cousin;T. Hellweg;J. Oberdisse
用小角中子散射研究了核-壳微凝胶中氘代聚（N，n-丙基丙烯酰胺）壳单体的径向密度分布，以揭示其线性热致溶胀的起源。的聚（N-异丙基甲基丙烯酰胺）的核心单体已经对比度匹配的H2O/D2 O溶剂混合物，和强度，从而提供了一个直接测量的壳单体的空间分布。简单的建模表明，它们的结构并不符合预期的定义明确的外壳。一个多壳层模型解决了一个反向蒙特卡罗方法，然后应用到提取的单体密度作为温度和核心交联的函数。据发现，大多数壳单体填充在高温接近塌陷颗粒的合成条件下的核心，只形成一个稀释的电晕。由于核单体倾向于在较低温度下溶胀，不溶性壳单体的骨架阻碍溶胀，从而诱导渐进的线性热响应。
The radial density profile of deuterated poly(N,n-propyl acrylamide) shell monomers within core-shell microgels has been studied by small-angle neutron scattering in order to shed light on the origin of their linear thermally-induced swelling. The poly(N-isopropyl methacrylamide) core monomers have been contrast-matched by the H2O/D2O solvent mixture, and the intensity thus provides a direct measurement of the spatial distribution of the shell monomers. Straightforward modelling shows that their structure does not correspond to the expected picture of a well-defined external shell. A multi-shell model solved by a reverse Monte Carlo approach is then applied to extract the monomer density as a function of temperature and of the core crosslinking. It is found that most shell monomers fill the core at high temperatures approaching synthesis conditions of collapsed particles, forming only a dilute corona. As the core monomers tend to swell at lower temperatures, a skeleton of insoluble shell monomers hinders swelling, inducing the progressive linear thermoresponse.