Simultaneous photoluminescence import and mechanical enhancement of polymer films using silica-hybridized quantum dots

Abstract

Quantum dot (QD)-polymer nanocomposites that simultaneously possess stable photoluminescence and enhanced mechanical properties are presented for the first time based on the facile blending of the ultrasmall silica-hybridized CdTe QDs (SiO2-h-QDs) or 3-(trimethoxysilyl)propyl methacrylate-modified SiO2-h-QDs (SiO2-h-QD-MSMAs) with polymer. Typically, for SiO2-h-QD-MSMA/poly(methyl methacrylate) (PMMA) nanocomposite films, the tensile strength, Young's modulus, and elongation at break improved by about 46%, 74% and 6%, respectively, upon the loading of only 0.2 wt% of SiO2-h-QD-MSMAs. It is found that the mechanical enhancement effect of the silica-hybridized QDs is general for both hydrophilic polymers such as polyvinyl alcohol and hydrophobic polymers such as PMMA or polystyrene due to the strong interfacial adhesion between SiO2-h-QDs and polymer matrix as well as the fine dispersibility of the nanofillers in composites. SEM measurements showed a ductile-rupture behavior for the materials in which the surface-modified nanofillers were well compatible with the polymer matrix, but a brittle-rupture behavior for the composites loaded with pristine nanofillers due to their local aggregation. The loading of silica-hybridized QDs simultaneously endowed the composites with desired and stable optical properties. No obvious decreases of both photoluminescence and transparency were found for the nanocomposite films exposed to daylight even for one year. Such dual functional SiO2-h-QD-polymer nanocomposites promise great potential to upgrade the conventional polymer materials.