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The bridged silsesquioxane hybrid materials and their metal complexes preparation and performance research

Author: LvZhiQing
Tutor: JiangJianXiong
School: Hangzhou Normal University
Course: Organic Chemistry
Keywords: bridged polysilsesquioxanes imine bipyridine metal-coordination polymer magnetic properties
CLC: O634.41
Type: Master's thesis
Year: 2010
Downloads: 50
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Abstract

Bridged polysilsesquioxanes are a kind of novel hybrid material, which exhibit many excellent properties. The general formula of their precursors is (R’O)3Si-R-Si-(OR’)3, where R’ stands for alkyl while R represents an organic functional group. The organic bridging group covalently bond to the component by Si-C bond throughout the whole material. Compared to normal hybrid materials, there is no two-phase separation and weak interfacial bonding occuring in bridged polysilsesquioxanes. It combines excellent mechanical properties, heat resistance of inorganic materials and good flexibility, high intensity of organic materials together and is superior to those of ordinary hybrid materials. Bridged polysilsesquioxanes have been widely applied as chiral catalyst support and mesoporous materials. It also has attracted increasing attention in the field of metal absorption materials and metal-coordinated functional materials in recent years. Generally, this kind of bridged materials always posseses special atoms (N,O, S, etc.), which have a strong coordination ability with metal ions. However, most studies have focused on those of photo-electric materials and heavy metal absorption materials. In this paper, the preparation of two serieses of novel bridged polysilsesquioxanes and their metal coordination polymer based on aromatic imine and bipyridyl are presented. Their thermal properties, structure properties and magnetic properties were investigated. Some significant results were also obtained. The main results are outlined below:(Ⅰ) Bridged polysilsesquioxanes 2,2’-PSBBS-(3a,b)、4,4’-PSBBS (3’) and their metal coordinated polymer 2,2’-PSBBS-Ni (4a,b)、4,4’-PSBBS-Ni (4’) were prepared by sol-gel method from three kinds of aromatic imine-bridged silsesquioxanes and Nickle salt (Nickel acetate) under the catalysis of diluted hydrochloric acid. The structures of the coordinated polymers were verified with infrared ray spectrometry, ultraviolet spectrometry and elemental analysis. It was found that the corresponding absorption peak of the coordinated polymer showed an obvious red shift. At the same time, the properties of these polymers were investigated with thermogravimetric analysis (TGA), scanning electron microscope (SEM) and X-ray diffraction (XRD). The TGA results suggested that the thermal stabilities were improved compared to those of corresponding bridged polysilsesquioxanes. Based on the SEM images, it was displayed that the homogeneous and spherical particles were formed. From the XRD investigation, it was found that the coordinated polymer were all amorphous and non-crystalline. The fact that there were no diffractive signals in the small-angle XRD also suggested that they were not mesoporous materials. The magnetic properties of the three imine-bridged polysilsesquioxanes and their coordinated polymers were examined. The Courier temperature was above zero, which means they all showed ferromagnetism. The fact that 2,2’-PSBBS-Ni (4a) exhibited large coercive force (1820 Oe), remanent magnetization (2.51emu/g) and area of magnetic hysteresis loop suggested a hard-ferromagnet. However,2,2’-PSBBS-Ni (4b) and 4,4’-PSBBS-Ni (4’) were a soft- ferromagnet. It is worth noting that there existed a transition temperature at 70K for 4,4’-PSBBS-Ni (4’), above which it was a diamagnet and below a ferromagnet.(Ⅱ) Bridged polysilsesquioxanes BPYPBS together with its metal coordinated polymer (BPYPBS-Ni2+) and (BPYPBS-Tb3+) were also prepared by sol-gel technology from bipyridyl-bridged silses- quioxanes and the nickle salt (Nickel acetate) or terbium salt (Terbium chloride) under the catalysis of diluted hydrochloric acid. The structure and properties of the polymers were characterized through the same method as described in section (Ⅰ). The results showed that the thermal stabilities of the coordinated polymers were also improved compared to those of bridged polysilsesquioxanes. SEM images showed that the surfaces were homogeneous and the globular particles were also congregated together. In addition, all of them were amorphous and had no mesostructure.The magnetic properties of the two coordinated polymers were tested and both exhibited ferromagnetism. BPYPBS-Ni2+ was a hard-ferromagnet due to its large values of coercive force (1290 Oe), remanent magnetization (7.24 emu/g) and area of magnetic hysteresis loop. However, BPYPBS-Tb3+ was a soft-ferromagnet ascribed to its small values of coercive force (18.74 Oe), remanent magnetization (0.01 emu/g) and area of magnetic hysteresis loop.

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