用正电子湮没谱学技术表征一种有机-无机杂化膜

Positron annihilation spectroscopy characterize PDMS-MIL-101 hybridmembrane

应用正电子湮没寿命谱(Positron annihilation lifetime spectroscopy,PALS)和正电子湮没符合多普勒展宽能谱(Coincidence Doppler broadening energy spectroscopy,CDBES)等正电子湮没谱学技术能从微观尺度上对聚合物-金属有机骨架材料杂化膜的微观结构进行表征。结果表明,随着金属有机骨架(Metal-Organic Frameworks,MOFs)添加量的增大,杂化膜中较小的和较大的自由体积的尺寸都减小了;杂化膜的正电子湮没符合多普勒展宽能谱显示,MIL-101(Material Institute Lavoisier-101)亚纳米粒子的加入使得正电子在聚二甲基硅氧烷(Poly(dimethyl siloxane),PDMS)氧原子上的偏向湮没效应减弱,部分正电子与来自MIL-101亚纳米粒子中金属原子的电子发生湮没,表明MOFs加入改变了聚合物基体自由体积周围的化学环境。

Background： Due to the integration of the advantages of the inorganic filler phase and the polymer phase, the organic-inorganic hybrid membrane, which can overcome the trade-off effect between permeability and selectivity, is widely used in many areas. Purpose： The aim is to study the microstructure of the PDMS-MIL-101（Cr） （Poly （dimethyl siloxane）-Material Institute Lavoisier-101（Cr））, which is a polymer-metal organic framework （MOFs） materials hybrid membrane. Methods： Positron annihilation lifetime spectroscopy （PALS） and coincidence Doppler broadening energy spectroscopy （CDBES） were used. Results： PALS results showed that the size of both the space at cross linking site and the free volume of polymer matrix decreased when the MIL-101（Cr） keep increasing, which indicates that MOFs penetrated into the free volume of polymer. Moreover, according to the CDB ratio spectra of hybrid membranes to single silicon crystal, it can be found that the effect of positron preferential annihilation with oxygen atoms was weakened with much more MIL-101（Cr） in hybrid membranes, and a fraction of positrons annihilated with the electrons of metal atoms locating at the center of subnanometer particles of MIL-101（Cr）. It is inferred that after entering the free volume of polymer, MIL-101 （Cr） particles may interact with oxygen atoms, thus partly block the way for positron＇s access to oxygen atoms. Conclusion： Positron annihilation technique is proved to be effective to characterize the microstructure of organic-inorganic hybrid membranes.