Polyhedral Oligomeric Silsequioxane Research Articles

On the Origin of Green Emission in Polyfluorene Polymers: The Roles of Thermal Oxidation Degradation and Crosslinking

AbstractThe green emission of poly(9,9′′‐dioctylfluorenyl‐2,7′′‐diyl), end‐capped by polyhedral oligomeric silsequioxanes, (PFO‐POSS) has been investigated by photoluminescence (PL) and photoexcitation (PE), gel permeation chromatography (GPC), and transmission Fourier transform infrared (FTIR) spectroscopy. The green emission is closely correlated with thermal oxidation degradation and crosslinking of the polymer and is enhanced by annealing at elevated temperatures. The green‐to‐blue emission intensity ratio, used to assess the emission properties of thin (90 nm) films, was 3.70, 4.35, and 1.54 for an air‐annealed film, its insoluble residue (crosslinked), and a film cast from its soluble portion, respectively. For thick (5–6 μm) film, the ratios are 13.33, 13.33, and 0.79, respectively. However, FTIR spectroscopy of thick films leads to the conclusion that the carbonyl‐to‐aromatic ring concentration ratio are 0.018, 0.015, and 0.032, respectively. Focusing on the recast films, the green emission is relatively low while the carbonyl concentration is relatively high. This suggests that the energy traps at crosslinked chains play an important role in green emission. It is likely that the crosslinking enhances the excitation energy migration and energy transfer to the defects by hindering chain segment twisting.

Crystal Structure of Polyhedral Oligomeric Silsequioxane (POSS) Nano-materials: A Study by X-ray Diffraction and Electron Microscopy

The crystal structure and morphology of inorganic−organic hybrid POSS nanoparticles, consisting of an inorganic core of silicon and oxygen and outer organic attachments of alkyl groups, has been studied using X-ray diffraction and electron microscopy. These molecules self-assemble to form a hexagonally packed structure. Alkyl attachments are accommodated within the interstices of the hexagonal lattice. The results have implications for our understanding of the disorder in polymer−POSS nanocomposite materials such as those formed by copolymerization.

Significant glass transition temperature increase based on polyhedral oligomeric silsequioxane (POSS) copolymer through hydrogen bonding

A series of poly(vinylphenol-co-vinylpyrrolidone-co-isobutylstyryl polyhedral oligosilsesquioxane (PVPh-co-PVP-co-POSS) copolymers were prepared by free radical copolymerization of acetoxystyrene, vinylpyrrolidone with POSS (PAS-co-PVP-co-POSS) following by selective removal of the acetyl protective group, and results in significant glass transition temperature increase. The thermal properties and hydrogen bonding of these copolymers were investigated by differential scanning calorimetry and fourier transfer infrared spectroscopy and good correlation between thermal behaviors and infrared spectroscopy results were observed.

Surface modification via 'lock and key' specific self-assembly of polyhedral oligomeric silsequioxane (POSS) derivatives to modified gold surfaces.

Diaminopyridine (DAP) functionalized POSS derivatives self-assemble on thymine functionalized monolayers on gold surfaces affording hybrid inorganic/organic surfaces.

Self-assembly of gold nanoparticles through tandem hydrogen bonding and polyoligosilsequioxane (POSS)-POSS recognition processes.

Diaminopyridine-functionalized polyhedral oligomeric silsequioxanes (POSS-DAP) self-assemble with complementary thymine-functionalized Au nanoparticles (Thy-Au) into well-defined spherical aggregates, providing highly structured nanocomposites.