基于多面体低聚倍半硅氧烷体系的一种独特发光现象

实验发现将2种POSS（多面体低聚倍半硅氧烷）单体氨苯基异丁基POSS和八异丁基POSS置于四氢呋喃搅拌加热后,原来不发光的POSS单体表现出较强的发光。为解释这个发光现象,我们对溶剂处理前后的POSS材料进行了结构和发光性能表征,通过¹HNMR、²⁹Si NMR及红外光谱等方法表征了POSS材料在THF中加热处理前后的结构,实验结果表明,这两种POSS在处理前后结构几乎没有变化,可以保持完整的笼状结构,但处理后的POSS分子¹H NMR谱中含有少量的溶剂峰。FTIR结果也表明处理前后的POSS结构几乎不变;我们也通过XPS表征了处理后的POSS中Si原子的价态,结果表明其价态未发生变化。结合这两种POSS材料处理前后的发光性能以及结构表征结果,我们认为,这种发光现象可能与POSS的吸附效应有关,即溶剂分子进入POSS笼中,形成POSS/溶剂加合物,从而改变了原来的POSS的电子结构,使得相应的POSS材料出现发光现象。

A Unique Luminescence Behavior Based on Polyhedral Oligomeric Silsesquioxane Compounds

In this study, an unusual luminescence behavior from two polyhedral oligomeric silsesquioxane (POSS) monomers, aminopropyl isobutyl POSS (AIPOSS) and octal isobutyl POSS (OIPOSS) was observed after heating and stirring in their tetrahydrofuran (THF) solution. The chemical structures of these POSS samples were characterized before and after the heat treatment in THF by means of ¹H and ²⁹Si nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The valence state of silicon in the POSS sample was determined by X-ray photoelectron spectroscopy (XPS) as well. The characterization results showed that there is no obvious change in their structures, except tiny difference of the ¹H NMR spectra. Photoluminescence (PL) properties of the treated/untreated POSS were studied in detail. According to the PL and structure characterization results, it is speculated that this unusual luminescence from the treated POSS is most likely caused by the adsorption effect of the POSS cage, forming the POSS/solvent adducts, which lead to the change of the electronic structure of the POSS, and consequently the luminescence of the treated POSS.