Four polyhedral oligomeric silsesquioxane (POSS) macromers, R7Si8O12styrene (R=isobutyl, cyclopentyl, cyclohexyl, or phenyl), containing a single polymerizable styrene unit were synthesized from the POSS-trisilanols R7Si7O9(OH)3 in a high yield and purity. The base-assisted reaction to produce these macromers appears to be general for POSS-trisilanols of this type. However, in some cases it may be necessary to control the rate at which the base is introduced during reaction to prevent unwanted side reactions that decompose the trisilanol. Cyclohexyl-, cyclopentyl-, and isobutyl-substituted POSS-stryenes (at 30 wt% or approximately 4 mol% loadings) undergo free radical bulk polymerizations with styrene to produce polymers that show variation in the modulus above the glass transition temperature. The phenylPOSS derivative is too insoluble in styrene to undergo this polymerization. The effect on the modulus is more pronounced for the copolymers containing 30 wt% cycloalkylPOSS than that seen with isobutylPOSS, which is similar to that for bulk polymerized polystyrene. The effect of the group at the POSS cage on bulk polymer properties has been noted before and is presumed to arise from differences in polymer microstructure. 相似文献
Shape memory polymer nanocomposite of EOC-EPDM blend has been prepared by the incertion of two different types of POSS nanoclay namely octaisobutyl POSS and trisilanolIsobutyl POSS. Compared to TSIB POSS, OIB POSS shows significant impact upon the shape memory behaviour of the blend. With increasing amount of POSS nanoclay, reduction in percentage shape fixity is lower for the nanocomposite containing OIB POSS rather than the TSIB POSS containing nanocomposite. On the other side, presence of closed cage like structure also results higher shape recovery ratio and lower shape recovery induction time for OIB POSS containing nanocomposite. 相似文献
Polyhedral oligomeric silsesquioxanes epoxy resin (POSSER) was prepared from 3-glycidypropyl-trimethoxysilane (GTMS) and tetramethylammonium hydroxide (TMAH) by hydrolytic condensation. POSSER was characterized using Fourier-transformed infrared spectroscopy (FTIR), 1H-NMR, and liquid chromagraphy/mass spectrometry (LC/MS). The epoxy value of POSSER is 0.50 mol/100 g. The LC/MS analysis indicated that T10 is the majority and contain some amount of T8, besides, a trace T9 also exists. The curing kinetics of POSSER with 4,4′-diaminodipheny sulfone (DDS) as a curing agent was investigated by means of differential scanning calorimetry (DSC). The curing reaction order n is 0.8841 and the activation energy Ea is 61.06 kJ/mol from dynamic DSC analysis. Thermal stability and kinetics of thermal degradation were also studied by thermal gravimetric analysis (TGA). TGA results indicated that the temperature of POSSE/DDS system 5% weight loss is approximately 377.0°C, which is higher by 12.6°C than that of pure POSSER, and the primary degradation reaction (300–465°C) followed first order kinetics; the activation energy of degradation reaction is 75.81 kJ/mol. 相似文献
The influence of the functionalization of fully condensed POSS cages on the properties of POM‐based nanocomposites is studied. POSS with different organic substituents [glycidylethyl, aminopropylisobutyl, and poly(ethylene glycol)] are taken into account and melt mixed with POM. Good dispersion was achieved upon the addition of amino functionalized POSS, leading to an increase on the thermal decomposition temperature under nitrogen atmosphere up to 50 °C. However, µm‐size aggregates were observed for other nanocomposites. There is no significant change in other thermal properties of the nanocomposites. The relationships among these effects and the morphological characteristics of the systems were analyzed.
A series of novel PDMS composites filled with a given amount of fumed silica were first prepared using divinyl-hexa[(trimethoxysilyl)ethyl]-POSS as cross-linker by hydrolytic condensation in the presence of organotin catalyst. The crosslinking reaction, the morphology, thermal behaviors and mechanical properties of the novel PDMS composites were characterized by attenuated total reflection infrared spectroscopy, scanning electron microscope, thermogravimetric analysis and universal tensile testing machine, respectively. It was found that the resistances to thermal degradation, thermo-oxidative decomposition of the novel PDMS composites were greatly improved by incorporation of POSS cross-linker, compared with that of the reference material (MT-1). Meanwhile, we also found that their thermal properties and mechanical properties were gradually enhanced with the further increment in loading amount of POSS cross-linker. The pronounced enhancements in thermal properties and mechanical properties of novel PDMS composites were likely attributed to the increasing interaction of PDMS chains and aggregated particles from synergistic effect between POSS and fumed silica. 相似文献
