Organic-inorganic hybrids are an important class of new materials that offer improved thermal and mechanical properties over normal polymers. They may be produced by either the sol-gel route or through the use of inorganic compounds possessing reactive functional groups. Polyhedral oligosilsesquioxanes (POSS) are completely defined molecules of nanoscale dimensions that may be functionalized with reactive groups suitable for the synthesis of new organic-inorganic hybrids. Here we report the synthesis and characterization of a novel POSS possessing eight isocyanate groups via the hydrosilylation of octakis(hydridodimethylsiloxy)octasilsesquioxane (Q8M8H) and m-isopropenyl-alpha,alpha'-dimethylbenzyl isocyanate (m-TMI). The suitability of this new macromer to the synthesis of a organic-hybrids has been explored by forming a new type of highly cross-linked polyurethane elastomer via reaction of the macromer with poly(ethylene glycol) using dibutyltin dilaurate catalyst.
We herein report the synthesis of organic−inorganic hybrid poly(methyl methacrylate) containing
polyhedral oligosilsesquioxanes. Octakis(3-hydroxypropyldimethylsiloxy)octasilsesquioxane (OHPS) was
synthesized from octakis(hydridodimethylsiloxy)octasilsesquioxane [Si8O12(OSiMe2H)8, Q8M8
H] following
literature procedures. Octakis(methacryloxypropyldimethylsiloxy) octasilsesquioxane (OMPS) was
synthesized via the reaction of methacryloyl chloride or methacrylic acid anhydride with OHPS, with
the latter giving improved purity. Polymerization of OMPS with methyl methacrylate using a
dibenzoylperoxide initiator gave a highly cross-linked polymer. Characterization of the polymer was
performed using Fourier transform IR spectroscopy, 29Si NMR, differential scanning calorimetry,
thermogravimetric analysis, atomic force microscopy, and transmission electron microscopy with energy-dispersive X-ray analysis. The polymer was found to be largely homogeneous. Increasing the OMPS
concentration in the polymer gave increased decomposition and glass transition temperatures.
Pseudo-boehmite has been functionalised with L-lysine by refluxing an aqueous solution containing these two reactants overnight. The resulting nanosized (<10 nm) product is insoluble in water and has been characterised by solid-state NMR spectroscopy, powder X-ray diffraction analysis, N 2 adsorption-desorption analysis and zeta potential measurements. The affinity of this new nanostructured organic-inorganic hybrid material for anionic dyes has been quantified using UV-vis spectrophotometry and by constructing the adsorption isotherms for Acid Blue 9 (AB9), Acid Yellow 23 (AY23), and Acid Red 37 (AR37). Elemental/micro analyses indicate that one lysine molecule is covalently bonded to every 8 nm 2 of the functionalised material giving a composition [(AlOOH) 230 $(H 2 O) 86 $(C 6 N 2 O 2 H 15)]. The introduction of the positively charged amino groups resulted in a tremendous increase in dye affinity in contrast to the unfunctionalised material. The adsorption isotherms of the functionalised pseudo-boehmite were fitted to the Langmuir model and yielded equilibrium binding constants (K a) of 2.6 Â 10 3 M À1 for AB9, 1.5 Â 10 5 M À1 for AY23 and 8.4 Â 10 4 M À1 for AR37. AR37 gave a higher monolayer coverage (C m) value of 0.13 mmol g À1 than AB9 (0.085 mmol g À1) and AY23 (0.081 mmol g À1). Dye adsorption is correlated with surface coverage of L-lysine and, in the case of AR37, two dye molecules are concluded to be adsorbed per L-lysine while for AY23 a multi-point interaction is proposed to result in a lower dye capacity and a relatively higher affinity of this dye for FPB when compared with AR37.
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