Study on the aggregation behavior of polyhedral oligomeric silsesquioxane compounds in solution

Ordered lamellar hybrid membranes are of great interest, due to their application as functional materials, including molecular sieving, biosensors, optical devices, and drug, as well as gene delive...

Three novel amphiphilic dicephalic (double-headed) surfactants containing oligo(ethylene-oxide)methyl-ether and a sugar moiety TGA-m (m = 1, 2, and 3) that incorporate a tetrasiloxane at the terminus of a hydrocarbon chain were designed and synthesized. Their surface activity and aggregation behavior in aqueous solution were systematically investigated by surface tension, dynamic light scattering (DLS), and transmission electron microscopy (TEM) techniques at 298 K. The surface tension measurements provided the critical aggregation concentration (CAC) and the surface tension at the CAC (γ(cac)). In addition, with application of the Gibbs adsorption isotherm, the maximum surface excess concentration (Γ(max)) and the minimum surface area/molecule (A(min)) at the air-water interface were estimated. The effect of EO chain length on the surface activity and aggregation behavior was also investigated. It was found that both the γ(cac) and the CAC were lower than those for reported traditional hydrocarbon surfactants. Aggregates of three surfactants, TGA-m (m = 1, 2, and 3), formed in aqueous solutions could be assigned as spherical vesicles as suggested by analysis using DLS and TEM. Moreover the formation of vesicles can be confirmed by the encapsulation of bromophenol blue. These results indicate that these three surfactants have excellent efficiencies of vesicle formation and surface tension reduction in the aqueous phase.

Polyglycerol modified polysiloxane surfactants: Their adsorption and aggregation behavior in aqueous solution

The passivation layer, which is located between a pixel electrode and a data elec- trode, must provide sufficiently low parasitic capacitance and sufficient electrical insulation to reduce cross talk and signal distortion. The present demand for passivation materials for next-generation displays has created interest in substitutes with low dielectric constant, high transmittance, thermal stability, and patternability; these requirements cannot be met by the silicon nitride layer and silicon dioxide used currently. To meet these requirements, negative-tone patterning systems containing polyhedral oligomeric silsesquioxane (POSS) were developed by adopting two different approaches: use of POSS in the polymeric matrix and in the crosslinker. The polymeric matrix, poly(methacryl isobutyl POSS-r- hydroxy styrene), showed improved dielectric property and thermal stability. However, the POSS content was limited owing to poor solubility. A POSS crosslinker with epoxy func- tional groups was used along with phenol group containing polymeric matrices; poly(4- hydroxy styrene). It was possible to pattern the POSS crosslinker system by irradiating it with UV light and subjecting it to subsequent thermal treatment. With increasing POSS content, the crosslinked materials showed increased transparency, higher thermal stability, and lower dielectric constant. The system could also be patterned by irradiating it with UV through a patterned mask.

Synthesis, characterization and physicochemical properties of glycosyl-modified polysiloxane

Adsorption and aggregation behavior of surface active trisiloxane room-temperature ionic liquids

Butynediol-ethoxylate based trisiloxane: Structural characterization and physico-chemical properties in water

A novel strategy, recently developed by us, to use polyhedral oligomeric silsesquioxanes (POSS) as an anti-cancer drug carrier is presented. Anthracycline:POSS complexes were prepared by simple co-addition of doxorubicin (DOX) or daunorubicin (DAU) with hydrophilic POSS(OH)32. Co-delivery of POSS and anthracyclines led to higher anti-cancer activity towards HeLa (cervical cancer endothelial) and MCF-7 (human breast adenocarcinoma) cell lines. The obtained supramolecular hybrid complexes were characterised by nuclear magnetic resonance (NMR) spectroscopy (nuclear Overhauser effect spectroscopy [NOESY] and homonuclear correlation spectroscopy [COSY]), Fourier transform infrared spectroscopy (FTIR), and dynamic light scattering (DLS). The two-dimensional (2D) NOESY spectra of the complexes showed the cross-correlation peaks for hydroxyl groups of POSS (~4.3–4.8 ppm) with OH groups of DOX and DAU. FTIR showed that hydroxyl group of POSS can interact with amine and hydroxyl groups of DOX and DAU. The viability of HeLa and MCF-7 was analysed with the MTT assay to evaluate the cytotoxicity of free DOX and DAU and the relevant complexes with POSS at different molar ratios. At a low DOX concentration (2.5 µM), for molar ratios 1:1, 1:4, and 1:8 (POSS:DOX), the complexes showed two and three times higher cytotoxicity towards HeLa and MCF-7 cells, respectively, than DOX itself after both 24- and 48-h incubation. The 1 µM concentration for a 1:4 POSS:DOX molecular ratio and the 2.5 µM concentration for all complexes were more toxic towards MCF-7 cells than free DOX after 48-h incubation. In the case of POSS:DAU complexes, there was higher toxicity than that of free drug after 48-h incubation. It can be concluded that the formation of non-covalent complexes increases toxicity of anthracycline drugs towards Hela and MCF-7 cells. The novel complexes are inexpensive to prepare and more effective than free drugs at low systemic toxicity.

Aggregation behavior and complex structure between triblock copolymer and anionic surfactants

A new series of well-defined amphiphilic hybrid polymers of tadpole-shaped architecture with polyhedral oligomeric silsesquioxane (POSS) nanocage as the hydrophobic head and poly(glycerol methacrylate) (PGMA) as the hydrophilic tail (POSS-PGMA) has been synthesized via atom transfer radical polymerization (ATRP). The aminopropylIsobutyl POSS, a monofunctional POSS nanocage, was transformed into ATRP initiator by treating with 2-bromoisobutyrylbromide. The POSS-PGMA was achieved in two steps. First, solketal methacrylate (SMA) (the precursor monomer for GMA), synthesized by reacting solketal with methacryloyl chloride, was polymerized under typical ATRP conditions with THF as the solvent at 40 °C, employing the synthesized POSS based initiator, and CuCl/N,N,N,N,N-pentamethyldiethylenetriamine as the catalyst system. The size exclusion chromatography (SEC) chromatograms reveal monomodal molecular weight distributions and narrow polydispersity indices; suggesting that well-defined tadpole-shaped hybrid polymers have been achieved. This further confirms that the monofunctional POSS initiator is able to affectively polymerize SMA in a controlled fashion under ATRP conditions. In the second step, the obtained POSS-PSMA was transformed into amphiphilic POSS-PGMA by acid hydrolysis. The successful transformation could be verified by 1H NMR and FTIR spectroscopy. Finally, because of the amphiphilic nature, the obtained POSS-PGMA could self-assemble when dispersed in water as confirmed by measuring the critical aggregation concentration (CAC) by fluorescence spectroscopy, using pyrene as the fluorescence probe. The CAC was found to increase with increasing the PGMA chain length. The large hydrodynamic size of the self-assembled structures, as determined by the laser light scattering data, however, suggests that the aggregates are not of typical core-shell type micelles.

Four vinyl polyhedral oligomeric silsesquioxane (POSS) with different functionalities and cage structures, monovinyl‐POSS (monov‐POSS), divinyl‐POSS (div‐POSS), trivinyl‐POSS (triv‐POSS), and tetravinyl‐POSS (tetrav‐POSS) were prepared and blended into fiber‐reinforced ethylene propylene diene monomer (EPDM—EPDM/AF) in the form of chemical cross‐linking to obtain four modified composites with various cross‐linked network structures and cage structures to investigate the influences and improvement of cross‐linking network and cage structures on the mechanical, thermal stability and ablation resistance of EPDM/AF. The results showed that the POSS of multi‐functionality with small steric hindrance, such as tetrafunctional tetrav‐POSS, can most significantly improve mechanical properties of EPDM/AF by forming denser crosslinking network structures, and the tensile strength and elongation at break of EPDM/AF/tetrav‐POSS can be increased 73.3% and 42.1% compared with EPDM/AF, respectively. POSS that has a complete cage structure and enables the modified composites to obtain a relatively dense cross‐linked network structure, such as difunctional div‐POSS can more substantially enhance the thermal stability and ablative resistance of EPDM/AF with the LAR and MAR of EPDM/AF/div‐POSS reduced by 25.2% and 10.5% compared to EPDM/AF, respectively. High‐temperature thermal transition of four modified composites at gradient temperatures was investigated to explain the relationship between the structure of POSS and ablation properties.Highlights Four POSS with different functionalities and cage structures were designed. Mechanical and ablative properties were reinforced by four vinyl POSS. Multifunctional POSS can most significantly improve mechanical properties. Functionality and cage structure together influence ablative property. High‐temperature thermal transition of modified composites was investigated

POSS-based molecular fillers for simultaneously enhancing thermal and viscoelasticity of poly(methyl methacrylate) films

Here, the design, synthesis, and characterization of laser nanomaterials based on dye‐doped methyl methacrylate (MMA) crosslinked with octa(propyl‐methacrylate) polyhedral oligomeric silsesquioxane (8MMAPOSS) is reported in relation to their composition and structure. The influence of the silicon content on the laser action of the dye pyrromethene 567 (PM567) is analyzed in a systematic way by increasing the weight proportion of POSS from 1 to 50%. The influence of the inorganic network structure is studied by replacing the 8MMAPOSS comonomer by both the monofunctionalized heptaisobutyl‐methacryl‐POSS (1MMAPOSS), which defines the nanostructured linear network with the POSS cages appearing as pendant groups of the polymeric chains, and also by a new 8‐hydrogenated POSS incorporated as additive to the polymeric matrices. The new materials exhibit enhanced thermal, optical, and mechanical properties with respect to the pure organic polymers. The organization of the molecular units in these nanomaterials is studied through a structural analysis by solid‐state NMR. The domain size of the dispersed phase assures a homogeneous distribution of POSS into the polymer, thus, a continuous phase corresponding to the organic matrix incorporates these nanometer‐sized POSS crosslinkers at a molecular level, in agreement with the transparency of the samples. The silicon–oxygen core framework has to be covalently bonded into the polymer backbone instead of being a simple additive and both the silica content and crosslinked degree exhibit a critical influence on the laser action.

Development of novel dental nanocomposites reinforced with polyhedral oligomeric silsesquioxane (POSS)

Polymers containing POSS(polyhedral oligomeric silsesquioxane) nanostructures show improved properties such as thermal stability, mechanical properties and oxidation resistance. Polyacrylonitrile(PAN) is one of the most widely used precursors for carbon fibers. However, PAN homopolymer has poor chemical, mechanical and thermal properties. A certain amount of suitable acidic comonomers is incorporated into PAN during polymerization for enhancing the solubility, the spinnability and especially, the thermo-oxidative stabilization. Among the acidic comonomers, IA(itaconic acid) is the preferably and the most widely used one because of the presence of two carboxyl group, which provides more opportunities for the carboxyl groups to interact with the nitrile groups during stabilization. In this work, we used Octa amic acid POSS having two carboxyl groups, to improve the properties of PAN copolymer. We investigated the effect of POSS addition during polymerization on the thermal properties of PAN copolymer. P(AN-IA)/POSS was prepared in dimethylsulfoxide (DMSO) by solution polymerization. Thin films of P(AN-IA)/POSS were prepared by spin coater using solution cast technique. The films were stabilized at different temperatures for various holding time. The structural evolution and the thermal properties of P(AN-IA)/POSS were studied by Fourier transform infrared spectroscopy (FT-IR), wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). From those results, the cyclization of nitrile groups was found to be initiated at lower temperature with increasing POSS contents and stabilization proceeded at more moderate pace in P(AN-IA)/POSS than PAN.