用正电子湮没谱学技术表征一种有机-无机杂化膜
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摘要
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.
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.
引文
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15 刘蕴韬,陈东风.中国先进研究堆中子散射科学平台介绍[J].物理,2013,42(8):534-543LU Yuntao,CHEN Dondfeng.The neutron scattering platform of China’s Advanced Research Reactor[J].Physics,2013,42(8):534-543
16 Li Z,He G W,Zhao Y N,et al.Enhanced proton conductivity of proton exchange membranes by incorporating sulfonated metal-organic frameworks[J].Journal of Power Sources,2014,262:372-379
17 伍海彪,曹兴忠,吴建平,等.Fe-1.5wt%Cu合金中Cu纳米颗粒与微观缺陷热回复过程研究[J].核技术,2012,35 (9):656-660WU Haibiao,CAO Xingzhong,WU Jianping,et al.Microstructure in Fe-1.5wt%Cu alloy after thermal treatment[J].Nuclear Techniques,2012,35(9):656-660
18 Dutta D,Feldblyum J I,Gidley D W,et al.Evidence of positronium bloch states in porous crystals of Zn4O-coordination polymers[J].Physical Review Letters,2013,110(19):197403
19 Nagai Y,Nonaka T,Hasegawa M,et al.Direct evidence of positron trapping at polar groups in a polymer-blend system[J].Physical Review B,1999,60(17):11863-11866
2 Robeson L M.Polymer membranes for gas separation[J].Current Opinion in Solid State&Materials Science,1999,4(6):549-552
3 Robeson L M.Correlation of separation factor versus permeability for polymeric membranes[J].Membrane Science,1991,62(2):165-185
4 Freeman B D.Basis of permeability selectivity Trade-off relations in polymeric gas separation membrane[J].Macromolecules,1999,32(2):375-380
5 Baker R W.Future directions of membrane gas-separation technology[J].Industrial&Engineering Chemistry Research,2002,41(6):1393-1411
6 宋东升,杜启云,王薇,等.有机-无机杂化膜的研究进展[J].高分子通报,2010,(3):12-15SONG Dongsheng,DU Qiyun,WANG Wei,et al.Advances in qrganic-inorganic hybrid membranes[J].Polymer Bulletin,2010,(3):12-15
7 Ferey G,Mellot D C,Serre C,et al.A chromium terephthalatebased solid with unusually large pore volumes and surface area[J].Science,2005,309(5743):2040-2042
8 Hong D Y,Hwang Y K,Sere C,et al.Porous chromium terephthalate MIL-101 with coordinatively unsaturated sites:surface functionalization,encapsulation,sorption and catalysis[J].Advanced Functional Materials,2009,19(10):1537-1552
9 Bromberg L,Diao Y,Wu H.Chromium(III)terephthalate metal organic framework(MIL-101):HF-free synthesis,structure,polyoxometalate composites,and catalytic properties[J].Chemistry of Material,2012,24(9):1664-1675
10 Yu W C,Sung C S P.Mobility and the distribution of free volume in epoxy network by photo chromic labeling and probe studies[J].Macromolecules,1988,21(2):365-371
11 Royal J S,Torkelson J M.Photochromic and fluorescent probe studies in glassy polymer matrices.5.Effects of physical aging on bisphenol A polycarbonate and poly(vinyl acetate)as sensed by a size distribution of photo chromic probes[J].Macromolecules,1992,25(18):4792-4796
12 Nojima S,Roe R J,Rigby D.Combined small-angle neutron scattering-small angle X-ray scattering study of blends of styrene-butadiene block copolymer with deuteratedpolybutadiene[J].Macromolecules,1990,23(19):4305-4312
13 Jean Y C.Microcomputer program for analysis of positron annihilation lifetime spectra[J].Nuclear Instruments&Methods in Physics Research Section A-Accelerators,1996,374(2):235-244
14 Dlubek G,Saarinen K,Fretwell M.The temperature dependence of the local free volume in polyethylene and polytetrafluoroethylene:a positron lifetime study[J].Journal of Polymer Science Part B-Polymer Physics,1998,36(9):1513-1528
15 刘蕴韬,陈东风.中国先进研究堆中子散射科学平台介绍[J].物理,2013,42(8):534-543LU Yuntao,CHEN Dondfeng.The neutron scattering platform of China’s Advanced Research Reactor[J].Physics,2013,42(8):534-543
16 Li Z,He G W,Zhao Y N,et al.Enhanced proton conductivity of proton exchange membranes by incorporating sulfonated metal-organic frameworks[J].Journal of Power Sources,2014,262:372-379
17 伍海彪,曹兴忠,吴建平,等.Fe-1.5wt%Cu合金中Cu纳米颗粒与微观缺陷热回复过程研究[J].核技术,2012,35 (9):656-660WU Haibiao,CAO Xingzhong,WU Jianping,et al.Microstructure in Fe-1.5wt%Cu alloy after thermal treatment[J].Nuclear Techniques,2012,35(9):656-660
18 Dutta D,Feldblyum J I,Gidley D W,et al.Evidence of positronium bloch states in porous crystals of Zn4O-coordination polymers[J].Physical Review Letters,2013,110(19):197403
19 Nagai Y,Nonaka T,Hasegawa M,et al.Direct evidence of positron trapping at polar groups in a polymer-blend system[J].Physical Review B,1999,60(17):11863-11866