Silsesquioxane-based polymer properties

Polyhedral oligomeric silsesquioxanes (POSS) are known molecules having various structures [1] as seen in Fig. 1. However double-decker shaped silsesquioxane has not been obtained. POSS is an interesting class of monomers for the preparation of silicon-based polymers. In recent years, silsesquioxane-based polymers have received much attention because of their useful properties, which include heat resistance, mechanical stability, low dielectric constant, etc. [2, 3],... 

Synthesis of Silsesquioxane Based Polymers and Property of Their Polymers... 

Simionescu, B., Olaru, M., Aflori, M., and Cotofana, C. Silsesquioxane-based hybrid nanocomposite with self-assembling properties for porous limestones conservation. High Perform. Polym. 22 no. 1 (2010) 42-55. 

The synthesis and properties of star polymers and dendrimers functionalized with ferrocene units has attracted a great deal of attention. The synthesis of high-generation dendrimers functionalized with chiral ferrocenyl units in their structures has been reported. The chiroptical properties of this class of dendrimer was dependent on the number of ferrocenyl groups and their chemical environment, but not on their position within the dendrimer. Deschenaux has reported the synthesis of hquid crystalline ferrocene-based polymers prossessing an enantiotropic smectic A phase. Ferrocene-functionahzed cyclic siloxane (29) and silsesquioxane branched polymers have also been reported. A hyperbranched polymer with a cubic silsesquioxane core was used to mediate the electrocatalytic oxidation of ascorbic acid. 

Chapter 5 is a review of polyhedral oligomeric silsesquioxanes (POSS), hybrid POSS-organic copolymers, and POSS resin nanocomposites. Although silsesquioxanes have been known since tiie 1960s, only recently, through controlled synthesis and purification, have their structure and unique properties been determined and their useful applications been explored. This chapter is complemented by a discussion of the synthesis and properties of silica- and silsesquioxanes-containing polymer nanohybrids in Chapter 6. Chapter 7 involves a review of the preparation and characterization of siloxane-based polyviologens, polyurethanes, and divinylben-zene elastomers. 

Kessler D, Theato P (2008) Synthesis of functional inorganic-organic hybrid polymers based on poly(silsesquioxanes) and their thin film properties. Macromolecules 41 5237-5244... 

Broadband dielectric spectroscopy is a powerful tool to investigate polymeric systems (see [38]) including polymer-based nanocomposites with different nanofillers like silica [39], polyhedral oligomeric silsesquioxane (POSS) [40-42], and layered silica systems [43-47] just to mention a few. Recently, this method was applied to study the behavior of nanocomposites based on polyethylene and Al-Mg LDH (AlMg-LDH) [48]. The properties of nanocomposites are related to the small size of the filler and its dispersion on the nanometer scale. Besides this, the interfacial area between the nanoparticles and the matrix is crucial for the properties of nanocomposites. Because of the high surface-to-volume ratio of the nanoparticles, the volume fraction of the interfacial area is high. For polyolefin systems, this interfacial area might be accessible by dielectric spectroscopy because polyolefins are nonpolar and, therefore, the polymeric matrix is dielectrically invisible [48]. 

Computations have been carried out to better understand the structures and properties of these types of nanocomposites. One subject of particular interest is the observed enhanced gas transport performance of PDMS nanocomposite membranes containing layered silicates, which is not expected based on studies of magnetically alligned particles disuc-ssed in the next section. Clays have also been used to improve the properties of silsesquioxane polymers. ... 

Wang Zheng, Wu Wei, Zhong Yuhua, Ruan Mingzhu, and Hui Lin Lin. Flame-retardant materials based on phosphorus-containing polyhedral oligomeric silsesquioxane and bismaleimide/DBA with improved thermal resistance and dielectric properties. J. Appl. Polym. Sci. 132 no. 9 (2015) 41545-41555. 

ATRP from Silsesquioxane Initiators. In addition to silsesquioxanes with vinyl based monomeric units attached to corner silicon atoms, other species can be bonded to the cubes. One such example is the silsesquioxane shown in Scheme 7. Termed benzyl chloride functionalized polyhedral oligomeric silsesquioxane (benzyl chloride-POSS), the molecule contains seven cyclopentyl groups, which provide increased solubility in organic solvents, and one benzyl chloride moiety which can serve as an initiator for ATRP. Studies of such initiators may be of interest due to the bulky nature of the initiating species. Furthermore, the high temperature stability of the inorganic cubes may lend some interesting thermal properties to polymers initiated from it. 

It is of interest to determine the flame retardant effectiveness of shapes or types of nanoparticles other than layered silicates, to find what shape or type of nanoparticle is most effective for improving the flammability properties of commodity polymers. In this chapter, flammability properties of nanocomposites containing nanoscale oxides such as nanoscale silica particles and metal oxides, polyhedral oligomeric silsesquioxanes (POSSs), and carbon-based nanoparticles such as graphite, single-walled carbon nanotubes (SWNTs), multiwalled carbon nanotubes (MWNTs), and carbon nanofibers (CNFs) are described and a flame retardant mechanism of these nanoparticles is discussed. 

Ahmad Z., SarwarM.I, Mark J.E. Thermal and mechanical properties ofaramid-based titania hybrid composites. J. Appl. Polym. Res. 1998 70 297-302 Ahmad Z., Wang S, Mark J.E. ACS Symposium Series, Vol. 585, J.E. Mark, C. Lee, P.A. Bianconi, eds. American Ceramic Society Pnblisher, 1994, pp. 291-296 Baney R.H., Itoh M., Sakakibara A, Suzuki T. Silsesquioxanes. Chem. Rev. 1995 95 1409-1430 Bescher E., Mackenzie J.D. Hybrid organic-inorganic sensors. Mater. Sci. Eng. 1998 C6 145-154 Bescher E., Hoshino Y., Nishizawa Y., Cool K, Mackenzie J.D. The role of Fe in the thermal stabilization of Ormosils. J. Sol-Gel Sci. Technol. 2003 26 297-301 Blanco et al. Microstractnral and mechanical properties of sono-Ormosils. J. Sol-Gel Sci. Technol. 1998 13 451-155... 

Xu H, Kuo S-W, Lee J-S, Chang F-C (2002) Preparations, thermal properties, and Tg increase mechanism of inorganic/organic hybrid polymers based on polyhedral oligomeric silsesquioxanes. Macromolecules 35(23) 8788-8793. doi 10.1021/ma0202843... 

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