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Organic-Inorganic Composites Based on Poly(methyl methacrylate) and In Situ Generated Silsesquioxane Structures

Organic-inorganic composite materials could provide favorable combination of properties which can hardly be reached if only organic or inorganic components are used. Small amounts (several wt %) of nanometer-sized particles in polymer matrices can considerably influence mechanical, optical, heat-resistant, and other properties of these systems. One of the most common ways for nanoparticle preparation is the sol-gel process. The inorganic nanostructures can either be formed in situ simultaneously with organic polymer or they can be first prepared and then added to polymerizable monomers or to polymer solution. The presence of covalent bonding between organic and inorganic components reinforces interaction between components and improves the properties of hybrid materials . In this work, new organic-inorganic composite materials based on poly(methyl methacrylate), PMMA, and silsesquioxane structures were prepared by in situ bulk polymerization. The inorganic phase was generated from 3-glycidyloxypropyltrimethoxysilane (GLYMO) via sol-gel chemistry. Poly(oxypropylene)diamine was used as an epoxy opening agent, as basic catalyst for GLYMO condensation and as PMMA crosslinking agent. Chemical reactions in the systems of different methyl methacrylate /GLYMO molar ratio were studied by Fourier transform infrared analysis. The high degree of conversion of methoxysilyl groups to -Si-O-Si- linkages was confirmed by 29Si NMR, Fig.1. Composite morphology was studied by SEM. Composite with ca. 3% of inorganic phase (calculated as SiO1, 5) showed a discrete microstructure, Fig.2 (a), while composites with higher amount of inorganic phase (ca. 5 and 7 %) showed characteristic IPN morphology, Fig.2(b). Silsesquioxane structures formed as a result of GLYMO hydrolysis and condensation in the sol-gel process influences the glass transition temperature of PMMA. The composites have much better thermal stability than PMMA and showed excellent solvent (THF) resistance. Their surfaces are more hydrophilic than PMMA and they may have potential as damping materials.

Organic-Inorganic Composites; sol-gel; Poly(methyl methacrylate); Silsesquioxane Structures

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