Institute of Physical Chemistry, University of Münster, Corrensstrasse 28/30, 48149 Münster, Germany.
Solid State Nucl Magn Reson. 2011 May-Jun;39(3-4):142-50. doi: 10.1016/j.ssnmr.2011.03.005. Epub 2011 Mar 29.
Sol-gel systems were prepared by co-hydrolysis and co-condensation of tetraethoxysilane (TEOS) and phenyltriethoxysilane (PhTES). The sols were transferred into silica gels by Evaporation Induced Self-Assembly (EISA) or Aerosol Assisted Self-Assembly (AASA) using a laboratory spray-dryer. The structural properties such as porosity and homogeneity/microheterogeneity of these different systems are compared by N(2) sorption measurements, thermal analysis (TG, DTG and DTA), (29)Si MAS NMR and (29)Si{(1)H} CP MAS NMR. The cross polarization of the AASA gels can be described with the conventional I-S dynamics of a homogeneous proton spin bath. The EISA gels are heterogeneous, and the I-I(*)-S model, or a bimodal I-S model, was employed for the simulation of CP dynamics. Microheterogeneities are observed by (1)H-(29)Si cross polarization on an EISA sample, whereas rapid drying (AASA) transfers the corresponding sol into homogeneous xerogels. The EISA gels are microporous after calcination at 923 K, and the AASA gels are dense.
采用四乙氧基硅烷（TEOS）和苯基三乙氧基硅烷（PhTES）的共水解和共缩合制备溶胶-凝胶体系。通过蒸发诱导自组装（EISA）或气溶胶辅助自组装（AASA），使用实验室喷雾干燥器将溶胶转化为硅胶。通过氮气吸附测量、热分析（TG、DTG 和 DTA）、（29）Si MAS NMR 和（29）Si{（1）H} CP MAS NMR 比较这些不同体系的结构性质，如孔隙率和均一性/微不均匀性。AASA 凝胶的交叉极化可以用均匀质子自旋浴的常规 I-S 动力学来描述。EISA 凝胶是多相的，采用 I-I(*)-S 模型或双模态 I-S 模型对 CP 动力学进行模拟。在 EISA 样品上观察到（1）H-（29）Si 交叉极化的微不均匀性，而快速干燥（AASA）将相应的溶胶转化为均相干凝胶。在 923 K 下煅烧后，EISA 凝胶具有微孔，而 AASA 凝胶则致密。
