Trisilanolphenyl Polyhedral Oligomeric Silsesquioxane Research Articles

Structural and thermal behavior of a novel phenolic resin and its composite with excellent ablative performance

The heat resistance of existing phenolic resins cannot meet the requirements of the increasingly harsh spaceflight environment. Boron and silicon have been added to phenolic resins to improve the char yields. However, achieving both a high initial decomposition temperature and an outstanding char yield remains challenging. This study presented a strategy to regulate the methylene types of boron-containing phenolic resin (TBPR) by trisilanolphenyl polyhedral oligomeric silsesquioxane (TPOSS) and NaOH. Thermogravimetric analysis (TGA) in nitrogen of cured TBPR displayed remarkable thermal stability with an initial decomposition temperature of 450.0 °C and a char yield of 75.8 %. The effect of TPOSS and NaOH on the TBPR structure were further investigated using nuclearmagneticresonance (NMR) analysis and densityfunctionaltheory(DFT) calculation. The results indicated that TPOSS could attract sodium phenate and formaldehyde through hydrogen bonds, and greatly reduced the energy barrier of the phenol–formaldehyde resin para-addition. The formation of more p-p’ type methylene structures of phenolic resin profoundly contributed to the outstanding initial decomposition temperatures and char yield. TBPR matrix transformed into a stronger protective char layer, forming an effective thermal protection barrier. As a result, the mechanical strength and ablative resistance of the fiber-reinforced CF/TBPR composites were enhanced by the excellent thermal stability of TBPR matrix.

Catalyzing Benzoxazine Polymerization with Titanium-Containing POSS to Reduce the Curing Temperature and Improve Thermal Stability.

Trisilanolphenyl-polyhedral oligomeric silsesquioxane titanium (Ti-Ph-POSS) was synthesized through the corner-capping reaction, and Ti-Ph-POSS was dispersed in benzoxazine (BZ) to prepare Ti-Ph-POSS/PBZ composite materials. Ti-Ph-POSS could catalyze the ring-opening polymerization (ROP) of BZ and reduce the curing temperature of benzoxazine. In addition, Ti immobilized on the Ti-Ph-POSS cage could form covalent bonds with the N or O atoms on polybenzoxazine, improving the thermal stability of PBZ. The catalytic activity of the Ti-Ph-POSS/BZ mixtures was assessed and identified through 1H nuclear magnetic resonance (1H-NMR) and Fourier-transform infrared (FTIR) analyses, while thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) were used to determine the thermal properties of the composite. It was found that PBZ exhibited a higher glass transition temperature (Tg) and better thermal stability when Ti-Ph-POSS was added. The curing behavior of the Ti-Ph-POSS/BZ mixtures showed that the initial (Ti) and peak (Tp) curing temperatures sharply decreased as the content of Ti-Ph-POSS and the heating rate increased. The curing kinetics of these Ti-Ph-POSS/BZ systems were analyzed using the Kissinger method, and the morphology of Ti-Ph-POSS/PBZ was determined via scanning electron microscopy (SEM). It was found that the Ti-Ph-POSS particles were well distributed in the composites. When the content exceeded 2 wt%, several Ti-Ph-POSS particles could not react with benzoxazine and were only dispersed within the PBZ matrix, resulting in aggregation of the Ti-Ph-POSS molecules.

New Epoxy Thermosets Organic-Inorganic Hybrid Nanomaterials Derived from Imidazolium Ionic Liquid Monomers and POSS®Ph.

New epoxy-amine networks issue from epoxydized imidazolium ionic liquid monomers (ILMs) and isophorone diamine (IPD) were modified for the first time by incorporating unmodified trisilanol phenyl POSS® (POSS®Ph-triol) and two ionic liquid-modified POSS®Ph (IL-g-POSS®Ph) having chloride (Cl−) and bis-trifluoromethanesulfonimidate (NTf2−) counter anions. Then, 5 wt.% of unmodified and IL-modified POSS®Ph were introduced in order to develop new solid electrolytes. First, a homogeneous dispersion of the POSS®Ph aggregates (diameters from 80 to 400 nm) into epoxy networks was observed. As a consequence, ILM/IPD networks with glass transition temperatures between 45 and 71 °C combined with an enhancement of the thermal stability (>380 °C) were prepared. Moreover, a significant increase of the hydrophobic character and high oil repellency of the network surfaces were obtained by using IL-g-POSS®Ph (19–20 mJ.m−2), opening up promising prospects for surface coating applications. Finally, these new epoxy networks exhibited outstanding high ionic conductivities (from 3.4 × 10−8 to 6.8 × 10−2 S.m−1) combined with an increase in permitivity.

Preparation and Characterization of Transparent Polyimide Nanocomposite Films with Potential Applications as Spacecraft Antenna Substrates with Low Dielectric Features and Good Sustainability in Atomic-Oxygen Environments

Optically transparent polyimide (PI) films with good dielectric properties and long-term sustainability in atomic-oxygen (AO) environments have been highly desired as antenna substrates in low earth orbit (LEO) aerospace applications. However, PI substrates with low dielectric constant (low-Dk), low dielectric dissipation factor (low-Df) and high AO resistance have rarely been reported due to the difficulties in achieving both high AO survivability and good dielectric parameters simultaneously. In the present work, an intrinsically low-Dk and low-Df optically transparent PI film matrix, poly[4,4′-(hexafluoroisopropylidene)diphthalic anhydride-co-2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane] (6FPI) was combined with a nanocage trisilanolphenyl polyhedral oligomeric silsesquioxane (TSP-POSS) additive in order to afford novel organic–inorganic nanocomposite films with enhanced AO-resistant properties and reduced dielectric parameters. The derived 6FPI/POSS films exhibited the Dk and Df values as low as 2.52 and 0.006 at the frequency of 1 MHz, respectively. Meanwhile, the composite films showed good AO resistance with the erosion yield as low as 4.0 × 10−25 cm3/atom at the exposure flux of 4.02 × 1020 atom/cm2, which decreased by nearly one order of magnitude compared with the value of 3.0 × 10−24 cm3/atom of the standard PI-ref Kapton® film.

POSS-enhanced colorless organic/inorganic nanocomposite (CORIN®) for atomic oxygen resistance in low earth orbit

Copolymers and blends of polyhedral oligomeric silsesquioxane (POSS) and polyimides have been shown to resist atomic-oxygen (AO) attack, making them promising candidates as space-durable materials in the harsh oxidizing environment of low Earth orbit (LEO). CORIN® is a commercially available and colorless POSS–polyimide which has the desirable but uncommon property among polyimides that it may be dissolved in a solvent and applied at room temperature, thus making it possible to have a widely applicable clear coating for protection from AO in LEO. The physical properties of CORIN® have been largely characterized, but its AO resistance has received limited study. We have thus used a hyperthermal AO beam to expose CORIN® and other POSS-containing polyimides, 7.3 wt% and 9.1 wt% Si7O9 trisilanolphenyl POSS blended with poly(pyromellitic dianhydride-co-4,4′-oxydianiline), to characterize their resistance to AO attack. CORIN® was found to have a particularly low erosion yield that is ≲1% that of the ubiquitous satellite material, Kapton, which agrees favorably with a result from an experiment on the International Space Station. The other POSS-containing polymers exhibited somewhat higher erosion yields of 1.4 and 2.2% that of Kapton, respectively. Surface characterization of CORIN® showed that it remained relatively smooth during AO exposure and implied that a passivating silicon oxide was formed. The comparison of the AO effects on CORIN® and the other POSS–polyimides suggests that the net effect of AO on such POSS–polyimides depends on the density of Si atoms as well as the reactivity of the organic component of the polymer. This work adds to our confidence in the use of POSS-containing polymers in LEO and, especially, in very LEO, where the necessity of protecting satellite materials and components from AO attack is critical.

Atomic Oxygen-Resistant Polyimide Composite Films Containing Nanocaged Polyhedral Oligomeric Silsesquioxane Components in Matrix and Fillers

For the development of spacecraft with long-servicing life in low earth orbit (LEO), high-temperature resistant polymer films with long-term atomic oxygen (AO) resistant features are highly desired. The relatively poor AO resistance of standard polyimide (PI) films greatly limited their applications in LEO spacecraft. In this work, we successfully prepared a series of novel AO resistant PI composite films containing nanocaged polyhedral oligomeric silsesquioxane (POSS) components in both the PI matrix and the fillers. The POSS-containing PI matrix film was prepared from a POSS-substituted aromatic diamine, N-[(heptaisobutyl-POSS)propyl]-3,5-diaminobenzamide (DABA-POSS) and a common aromatic diamine, 4,4′-oxydianline (ODA) and the aromatic dianhydride, pyromellitic dianhydride (PMDA) by a two-step thermal imidization procedure. The POSS-containing filler, trisilanolphenyl POSS (TSP-POSS) was added with the fixed proportion of 20 wt% in the final films. Incorporation of TSP-POSS additive apparently improved the thermal stability, but decreased the high-temperature dimensional stable nature of the PI composite films. The 5% weight loss temperature (T5%) of POSS-PI-20 with 20 wt% of DABA-POSS is 564 °C, and its coefficient of linear thermal expansion (CTE) is 81.0 × 10−6/K. The former is 16 °C lower and the latter was 20.0 × 10−6/K higher than those of the POSS-PI-10 film (T5% = 580 °C, CTE = 61.0 × 10−6/K), respectively. POSS components endowed the PI composite films excellent AO resistance and self-healing characteristics in AO environments. POSS-PI-30 exhibits the lowest AO erosion yield (Es) of 1.64 × 10−26 cm3/atom under AO exposure with a flux of 2.51 × 1021 atoms/cm2, which is more than two orders of magnitude lower than the referenced PI (PMDA-ODA) film. Inert silica or silicate passivation layers were detected on the surface of the PI composite films exposed to AO.

Atomic oxygen durable ultra-black polyimide nanocomposite films in solar spectrum

Black thermal control blankets have been widely used in spacecraft for eliminating stray light around high-resolution optical instruments. However, the limited absorption in visible light range, the fast degradation upon hyperthermal atomic oxygen (AO) in low Earth orbit (LEO), and the poor adhesion of black coatings with substrate confined their applications into board solar spectrum and multi-layer interface engineering. In this work, a nanocomposite polyimide film containing a trisilanolphenyl POSS, a dye of solvent black 34, and a carbon black of CABOT M800 has been designed. With an ingredient of 20 wt% POSS, 5 wt% dye, and 10 wt% carbon black, the nanocomposite polyimide film PPIBC10 exhibited an ultra-low transmittance near zero in the range 200–2000 nm, a low reflectance below 5% in UV range and below 2% in VIS-IR range, and a low erosion yield of 0.49 ± 0.11 × 10−24 cm3 atom−1 upon a 2.27 × 1020 atoms cm−2 hyperthermal AO exposure, with an absorptance of 0.983, an emissivity of 0.86, and a coefficient of thermal expansion of 20 ppm oC−1. SEM and XPS analysis indicated that a uniform SiOx passivating network was formed on surface upon the hyperthermal AO exposure. The tensile strength decreased with increasing additives, and kept stable upon the AO exposure, for there was only sub-micrometer in erosion depth. The thermal expansion coefficients of the nanocomposite films are comparable to that of Kapton, which benefits interface engineering. The small granularity of tens of micrometers and good solubility in poly(amic acid) of additives POSS, dye, and carbon black benefit potential manufacture. This study suggests an ultra-black AO durable polyimide film for potential applications in LEO.

Self-Healing Anti-Atomic-Oxygen Phosphorus-Containing Polyimide Film via Molecular Level Incorporation of Nanocage Trisilanolphenyl POSS: Preparation and Characterization.

Protection of polymeric materials from the atomic oxygen erosion in low-earth orbit spacecrafts has become one of the most important research topics in aerospace science. In the current research, a series of novel organic/inorganic nanocomposite films with excellent atomic oxygen (AO) resistance are prepared from the phosphorous-containing polyimide (FPI) matrix and trisilanolphenyl polyhedral oligomeric silsesquioxane (TSP–POSS) additive. The PI matrix derived from 2,2’-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 2,5-bis[(4-amino- phenoxy)phenyl]diphenylphosphine oxide (BADPO) itself possesses the self-healing feature in AO environment. Incorporation of TSP–POSS further enhances the AO resistance of the FPI/TSP composite films via a Si–P synergic effect. Meanwhile, the thermal stability of the pristine film is maintained. The FPI-25 composite film with a 25 wt % loading of TSP–POSS in the FPI matrix exhibits an AO erosion yield of 3.1 × 10−26 cm3/atom after an AO attack of 4.0 × 1020 atoms/cm2, which is only 5.8% and 1.0% that of pristine FPI-0 film (6FDA-BADPO) and PI-ref (PMDA-ODA) film derived from 1,2,4,5-pyromellitic anhydride (PMDA) and 4,4’-oxydianline (ODA), respectively. Inert phosphorous and silicon-containing passivation layers are observed at the surface of films during AO exposure.

Phenolic resin/polyhedral oligomeric silsesquioxane (POSS) composites: Mechanical, ablative, thermal, and flame retardant properties

Three different polyhedral oligomeric silsesquioxanes (POSS), trisilanolphenyl polyhedral oligomeric silsesquioxane (T‐POSS), octaaminophenyl polyhedral oligomeric silsesquioxanes (OAPS), and octaphenyl polyhedral oligomeric silsesquioxanes (OPS) were incorporated into phenolic resin (PR), respectively; PR/POSS composites were successfully prepared, and the properties of PR/POSS composites were studied. The limiting oxygen index (LOI), cone calorimeter, and thermal gravimetric analysis (TGA) were used for the estimation of flame retardancy and thermal stability. Oxyacetylene flame test and flexural strength test were used to study the ablative and mechanical properties of the PR/POSS composites. The results indicated that T‐POSS was more effective in improving the flame retardancy of PR than OAPS or OPS. Meanwhile, compared with pure PR, the second line ablation rates of PR/4% T‐POSS, PR/4% OAPS, and PR/4% OPS were significantly reduced by 53.3%, 61.9%, and 40.0%, respectively. In addition, the thermal stability and flexural strength of PR/4% T‐POSS were significantly higher than that of all other PR composites.

Phosphate glass matrix composites incorporating trisilanol phenyl polyhedral oligomeric silsesquioxane prepared by viscous flow sintering method with enhanced benefits

The effect of mixing and sintering processes to prepare tin fluorophosphate glass (Pglass) matrix composites incorporating trisilanol phenyl polyhedral oligomeric silsesquioxane (TSP-POSS) was investigated by comparing manual and suspension mixing, one-step and stepwise sintering processes to explore the structure dynamics and physical properties in the composites as a function of the different process conditions used. Energy Dispersive X-ray analysis confirmed optimal homogeneous dispersion of the TSP-POSS molecules in the composites prepared by the suspension method. The observed increase of glass transition temperature and the reduction of non-bridging bonds in the composites are believed to be the reason for the effective dispersion of TSP-POSS molecules in the composites. The chemical reaction between the TSP-POSS and Pglass was strongly influenced by the mixing/dispersion and sintering processes investigated. 13C cross polarized magic angle spinning (CP MAS) solid state nuclear magnetic resonance (NMR) spectroscopy confirmed the chemical stability of the TSP-POSS during the sintering process at elevated temperatures. In addition, a chemical reaction between the TSP-POSS and Pglass was evidenced by 29Si CP MAS NMR analysis. This study will provide a better fundamental understanding of the effective dispersion mechanism of the TSP-POSS molecules in the Pglass matrix that will facilitate tailoring the physicochemical properties of the composites with addition of various small concentrations of TSP-POSS for a number of applications where the pure Pglass is not applicable due to the intrinsic properties of the Pglass.

Hyperthermal atomic oxygen durable transparent silicon-reinforced polyimide

A clear poly(amic acid) was reinforced by a trisilanolphenyl polyhedral oligomeric silsesquioxane (POSS) by direct dissolution, and transparent silicon-reinforced polyimide (Si-RPI) films with different POSS loadings were obtained after curing, showing high transmittance of >90% within 380–800 nm. The Si-RPI films were exposed to a ground hyperthermal atomic oxygen (AO) beam. The erosion depths and derived erosion yields of the materials decreased with POSS loadings. At a 20 wt% POSS loading, the Si-RPI showed an erosion yield of 0.13 × 10−24 cm3 atom−1 at a fluence of 2.79 × 1020 O atoms cm−2. Surface morphology and element composition characterization on Si-RPI indicated that SiOx-based passivating layers were formed on surfaces upon the hyperthermal AO attack. This study suggests a facile way of reinforcing Si into transparent polyimide for a promising candidate of spacecraft coating material operating in low Earth orbit.

Trisilanolphenyl-POSS nano-hybrid poly(biphenyl dianhydride-p-phenylenediamine) polyimide composite films: miscibility and structure-property relationship

A partially condensed polyhedral oligomeric silsesquioxane (POSS) compound, trisilanolphenyl-POSS (TSP-POSS) was prepared via a modified two-step procedure with phenyltrichlorosilane as the starting material. The solubility of the TSP-POSS in polyimide (PI) solvents, including N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) was first evaluated. TSP-POSS could be dissolved in the test solvents with a solid concentration higher than 50 wt% and the obtained solution was stable both at room temperatures and in refrigerator at -18 °C for more than 1 month. TSP-POSS was then physically blended with a poly(amic acid) (PAA) obtained from 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA) and para-phenylenediamine (PDA) with various adding proportions of 0, 5, 10, 15, 20, and 25 wt% (TSP-POSS in total solids). The obtained clear and homogeneous PAA/TSP-POSS solution was then thermally imidized at elevated temperatures to afford six PI/TSP-POSS composite films (PI-BP-0~PI-BP-25). For comparison, analogous composite films were prepared by blending TSP-POSS with another PI matrix, poly(pyromellitic anhydride-oxydianiline) (PIPMDA-ODA) at the same hybrid proportion (PI-0~PI-25). TSP-POSS exhibited quite different miscibility with these two PI matrixes. All of the composite films based on PIPMDA-ODA and TSP-POSS showed homogeneous nature and the films were optically transparent even at the high POSS loading of 25 wt%; however, the PIBPDA-PDA analogues showed poor compatibility with the POSS additive when the adding proportion was over 10 wt%. PI-BP-20 and PI-BP-25 films were thoroughly opaque with the haze values of 100%. In addition, the residual weight ratio of the composite films at 760 °C in nitrogen increased from 62.0 wt% (PI-BP-0) to 74.1 wt% (PI-BP-25).

Poly(2,5-benzimidazole)/trisilanolphenyl POSS composite membranes for intermediate temperature PEM fuel cells

Novel organic-inorganic composites were in-situ synthesized by using TriSilanolPhenyl polyhedral oligomeric silsesquioxane (SO-POSS) as fillers and poly(2,5-benzimidazole) (ABPBI) as polymer matrix. The uniformly dispersed 3% SO-POSS particles in ABPBI matrix increased the thermal stability of the composite membranes. It was found that both the water and H3PO4 uptakes were increased significantly with the addition of SO-POSS due to the formation of hydrogen bonds between the POSS and H2O/H3PO4, which played a critical role in the improvement of the conductivity of the composite membranes at temperature over 100 °C. Proton conductivities of H3PO4 doped with 3wt% SO-POSS contained ABPBI membranes increased with the increase of H3PO4 absorbance, reaching the maximum proton conductivity of 2.55 × 10-3 S·cm-1 at 160 °C, indicating that the ABPBI/SO-POSS composite membrane could be a promising candidate for mid-temperature PEMFCs.

Synthesis of a phosphorus-containing trisilanol POSS and its application in RTV composites

AbstractA novel trisilanol polyhedral oligomeric silsesquioxane-containing phosphorus (DPCP-TPOSS) was synthesized from trisilanolphenyl polyhedral oligomeric silsesquioxane (TPOSS) and diphenyl chlorophosphate. DPCP-TPOSS was characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), hydrogen nuclear magnetic resonance (1H-NMR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Then a novel type of room-temperature vulcanized silicone rubber (RTV)/DPCP-TPOSS composite was prepared. Properties such as swelling behavior, tensile strength, elongation at break, thermal stability and flame retardance were researched and compared. Results showed that RTV/DPCP-TPOSS-3 and RTV/DPCP-TPOSS-5 composites exhibited the best tensile strength and elongation at break, 4.5 MPa and 427%, which was 25% and 32% higher than that of pure RTV. TGA tests demonstrated that RTV/DPCP-TPOSS-3 owned the highest char residues, 39.7%. Tmax of RTV composites was increased from 531.9°C to 557°C with the incorporation of DPCP-TPOSS. Moreover, the addition of DPCP-TPOSS led to considerably increase of the fire-retardant performance.

Effect of POSS‐grafted titanium dioxide on the electrical and thermal properties of LDPE/TiO2 polymer nanocomposite

ABSTRACTTwo types of nanocomposites have been fabricated by a ball‐milling technique. The first type consists of untreated titanium dioxide (TiO2) incorporated into low‐density polyethylene (LDPE). For the second one, TiO2 filler chemically treated with trisilanol phenyl–polyhedral oligomeric silsesquioxane (TP–POSS) as compatibilizing agent was ball‐milled with LDPE. All specimens were tested by microstructure analysis and thermal, dielectric characterization techniques. Microstructure analysis by atomic force microscopy and scanning electron microscopy show clearly an increased dispersion in presence of POSS. Scanning electron microscopy even shows the formation of a particular structure due possibly to interactions between functionalization. It was observed that the modification of the surface of TiO2 by the POSS decreased the dielectric loss. All nanocomposites containing treated TiO2 revealed an improvement in thermal conductivity, with the most distinct value of 19% in case of LDPE containing 5 wt % treated TiO2. The incorporation of TiO2 fillers seems to reduce the dielectric breakdown strength of the nanocomposites. However, nanocomposites containing 3 and 5 wt % treated TiO2 have exhibited a slightly enhancement in dielectric breakdown strength up to 5%. The improvement in surface resistance to partial discharge was found in all nanocomposites specimens, especially for both types of composite containing 7 wt % untreated and treated TiO2. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46095.

Effect of trisilanolphenyl‐POSS on rheological, mechanical, and flame‐retardant properties of poly(ethylene terephthalate)/cyclotriphosphazene systems

ABSTRACTPoly(ethylene terephthalate) (PET) chips were coated by trisilanolphenyl–polyhedral oligomeric silsesquioxane (T‐POSS) and hexakis (para‐allyloxyphenoxy) cyclotriphosphazene (PACP) using the predispersed solution method, and PET/PACP/T‐POSS hybrids were further prepared by the melt‐blending method. The influence of T‐POSS on the rheological, thermal, and mechanical properties and flame retardancy of PET/PACP composites were discussed. The results suggest that T‐POSS was homogeneously dispersed in the PET matrix, which reduced the negative effects on polymer rheology and mechanical properties. For the PET/4%PACP/1%T‐POSS sample, the tensile strength at break and Tg increased from 29.67 MPa and 81.7 °C (PET/5%PACP) to 34.8 MPa and 85.8 °C, respectively, but the sample also self‐extinguished within 2 s, and the heat release capacity was reduced by 27.9% in comparison with that of neat PET.© 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45912.

Novel porous bioabsorbable phosphate glass matrix nanocomposites incorporating trisilanolphenyl polyhedral oligomeric silsesquioxane prepared by extrusion

Phosphate glass matrix nanocomposites containing trisilanolphenyl polyhedral oligomeric silsesquioxane (POSS) were investigated for the first time to accelerate efforts to develop novel hybrid phosphate glass/POSS composites with enhanced benefits. Tin fluorophosphate glass (Pglass) having ultra-low glass transition temperature (Tg) was utilized as the matrix material in extrusion at relatively low processing temperature (i.e., 270±10°C) compared to that of typical borosilicate and sodalime glasses. The resulting nanocomposites materials were highly porous due to evaporation of condensed water produced in situ from polysiloxane condensation reaction between the Pglass and POSS during the extrusion process. As the amount of POSS was increased in the Pglass matrix material, the glass transition temperature was significantly changed by the bulky POSS molecules. The novel porous nanocomposites should find a number of uses in applications at elevated temperatures where conventional organic polymer foam materials are not useable.

Improvement of thermal ageing and transparency of methacrylate based poly(siloxane–silsesquioxane) for optoelectronic application

ABSTRACTTrisilanolphenyl–polyhedral oligosilsesquioxane (trisilanolphenyl–POSS) structure is introduced into a polysiloxane network in an attempt to produce thermally stable material with improved transparency. A series of organic–inorganic resins comprised of diphenylsilanediol, 3‐methacryloxypropyl trimethoxysilane, and varying content of trisilanolphenyl–POSS were copolymerized through condensation followed by curing using phenyltris(hydrogendimethylsiloxy)silane as curing agent. Fourier transform infrared spectroscopy (FTIR), proton‐nuclear magnetic resonance spectroscopy (1H‐NMR), and silicon‐nuclear magnetic resonance spectroscopy (29Si‐NMR) were used to confirm the synthesized product. Excellent thermal stability, improved glass transition temperature (Tg), and lower coefficient of thermal expansion with the increasing POSS content were observed from thermomechanical analysis. Its extreme thermal degradation stability was attributable to the crosslinked network as well as the heavily substituted aromatic ring present in the system. Steric hindrance effect is noticeable beyond 5.66 mol % trisilanolphenyl–POSS content. Incorporation of POSS substituent in methacrylate‐based polysiloxane give excellent transparency and improved thermal discoloration resistance as deduced from UV/vis Spectrophotometer, making it a potential material to be used in optoelectronics. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45285.

Synthesis and characterization of novel phosphate glass matrix nanocomposites containing polyhedral oligomeric silsesquioxane with improved properties

The preparation and characterization of novel tin fluorophosphate glass (Pglass) matrix nanocomposite materials containing nanoscale trisilanolphenyl polyhedral oligomeric silsesquioxane (POSS) prepared via classical glass synthesis was investigated to accelerate efforts to develop novel hybrid Pglass/POSS nanocomposites with enhanced benefits in suitable diverse applications. The glass transition temperatures (Tg) of the obtained nanocomposites ranged from 121.6° to 147.6°C to an extent that depends on the nano-POSS concentrations (≤10wt% POSS) in the nanocomposites. The obtained scanning electron microscopy with energy-dispersive x-ray spectroscopy and atomic force microscopy results confirmed the homogeneous molecular level dispersion of the POSS cages in the continuous Pglass matrix of the nanocomposite. Chemical reaction (or bonding) between the constituents of the nanocomposites was confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance spectroscopy. The rheological (storage and loss modulus) and nanomechanical (elastic modulus) properties of the nanocomposites significantly improved with increasing nano-POSS concentrations up to 10wt% POSS. The molecular dispersion of the POSS and its strong physicochemical interaction with the continuous Pglass matrix can be tailored to satisfy requirements of a number of optomechanical applications where the pure glass is not useable.

Resistance of POSS Polyimide Blends to Hyperthermal Atomic Oxygen Attack.

Copolymers of polyhedral oligomeric silsesquioxane (POSS) and polyimide (PI) have shown remarkable resistance to atomic oxygen (AO) attack and have been proposed as replacements for Kapton on the external surfaces of spacecraft in the harsh oxidizing environment of low Earth orbit (LEO). POSS PI blends would be an economical alternative to the copolymers if they also resisted AO attack. Thus, blends of trisilanolphenyl (TSP) POSS and PI with different weight percentages of the Si7O9 POSS cage were cast into films and exposed to a hyperthermal AO beam, and they were characterized in terms of their recession, mass loss, surface morphology, and surface chemistry. In order to compare the AO resistance of the blends with POSS PI copolymers, samples of previously studied copolymers were also investigated in parallel with the blends. For all POSS PI materials, the AO resistance increased with increasing AO fluence and with increasing POSS cage loading. At similar POSS cage loadings and exposure conditions, the TSP POSS PI blends showed comparable erosion yields to the POSS PI copolymers, with specific samples of blends and copolymers achieving erosion yields as low as 0.066 × 10-24 cm3 atom-1 with an AO fluence of 5.93 × 1020 O atoms cm-2. SEM and XPS analyses indicated that passivating SiOx layers were formed on the surfaces of all POSS-containing polymers during AO exposure. Thus, a TSP POSS PI blend is proposed as a low-cost variant of a POSS polyimide for use in extreme oxidizing environments, such as LEO.