Oligosiloxane Resin Research Articles

A New Dealcoholization Method in the Synthesis of Vinyl Methyl Phenyl Silicone Resins for LED Encapsulation

The oligosiloxane resins were synthesized through hydrolytic sol-gel reaction and remained many hydroxyl groups, which did great harm to the curing process and resulted in poor performance of the cured products. In previous works, epoxy-modified silicone resins were synthesized by dealcoholization, a reaction between 3-glycidoxypropylmethyldimethoxysilane and terminal hydroxyl groups in phenyl silicone resins. Although this method eliminated the hydroxyl groups, it caused a large loss of vinyl groups inevitably and a poor stability of cured products. In this study, methyltrimethoxysilane (MTMS) was used to eliminate hydroxyl groups containing in vinyl methyl phenyl silicone resins, which were synthesized through hydrolytic sol-gel reaction. Most of residual hydroxyl groups were deleted effectively and the great loss of vinyl groups were avoided in the dealcoholization reaction. Then, the methyl phenyl silicone materials were fabricated by hydrosilylation reaction between the synthesized vinyl methyl phenyl silicone resins and hydrogen-containing ones. The cured silicone materials showed excellent optical performance (~ 89.1% at 450 nm) and good adhesion performance. In addition, due to less vinyl loss in the vinyl methyl phenyl silicone resins, the cured methyl phenyl silicone materials exhibited higher cross-linking density, better thermal resistance (5% mass loss at 435 °C) and better mechanical properties (50 shore D) compared with the epoxy-modified phenyl silicone materials. The lumen depreciation (working 168 h at 50 mA) and reflow soldering tests further demonstrated the methyl phenyl silicone materials possessed good thermal stability. These results indicated that the methyl phenyl silicone materials could be used as a LED encapsulant with a good performance.

Photo-Patternable Quantum Dots/Siloxane Composite with Long-Term Stability for Quantum Dot Color Filters.

Incorporation of quantum dots (QDs) into color filters (CFs) are desired for less energy loss and wider viewing angle compared to a conventional display. However, aggregation and vulnerability to heat, moisture, and chemicals in the photo-patternable matrix are critical issues of the QD-CFs with high QDs concentration. Herein, we fabricated red (10 wt %) and green (20 wt %) QD-CFs using photolithography of QD/siloxane ink containing secondary thiol monomer. Ligand-exchanged QDs were chemically incorporated in methacrylate oligosiloxane resin. QD/siloxane composite showed superior stability under harsh heat and moisture (85 °C/5% RH and 85 °C/85% RH) conditions and chemicals (EtOH, HCl, and NaOH) compared to conventional QD/PR (commercial negative photoresist). QD-CFs (10 μm thick) effectively converted blue light emitted from LED chip into red and green light, and the obtained white PL through QD-CF showed wide color gamut, which was 108% relative to NTSC. From these advantages, QD/siloxane composite will be beneficial as color-conversion photoresists are to be used as color filters in liquid crystal displays, micro light-emitting diodes, and organic light-emitting diodes.

Two-Step-Enhanced Stability of Quantum Dots via Silica and Siloxane Encapsulation for the Long-Term Operation of Light-Emitting Diodes.

Despite innovative optical properties of quantum dots (QDs) for QDs-converted light-emitting diodes (QD-LEDs), the vulnerability of the QDs, against heat and moisture, has been a critical issue for commercialization and long-term use. To overcome the instabilities, we fabricated a thermally and photostable QDs-embedded silica/siloxane (S-QD/siloxane) film by embedding QDs in silica and siloxane encapsulation through a two-step sol-gel reaction. S-QDs were stably dispersed in the oligo-siloxane resin with even a QD concentration of 5 wt % without aggregation. The two-step physical barriers of silica and siloxane acted to decrease the toxicity of QDs and improve the stability against heat and moisture [85 °C/5% relative humidity (RH), 85 °C/85% RH, and 120 °C/5% RH], light (50 and 100 mA), and chemicals (ethanol, HCl, and NaOH). Our S-QD/siloxane film was applied as a color-conversion material on a blue LED chip without additional solidification and encapsulation processes for red and white QD-LEDs, exhibiting a wider color gamut (107% in CIE 1931) compared to NTSC. These enhancements indicate that our S-QD/siloxane film is a suitable material for long-term operation of QD-enhanced films and QD-LEDs in next-generation displays.

Boehmite Nanofillers in Epoxy Oligosiloxane Resins: Influencing the Curing Process by Complex Physical and Chemical Interactions

In this work, a novel boehmite (BA)-embedded organic/inorganic nanocomposite coating based on cycloaliphatic epoxy oligosiloxane (CEOS) resin was fabricated applying UV-induced cationic polymerization. The main changes of the material behavior caused by the nanofiller were investigated with regard to its photocuring kinetics, thermal stability, and glass transition. The role of the particle surface was of particular interest, thus, unmodified nanoparticles (HP14) and particles modified with p-toluenesulfonic acid (OS1) were incorporated into a CEOS matrix in the concentration range of 1–10 wt.%. Resulting nanocomposites exhibited improved thermal properties, with the glass transition temperature (Tg) being shifted from 30 °C for unfilled CEOS to 54 °C (2 wt.% HP14) and 73 °C (2 wt.% OS1) for filled CEOS. Additionally, TGA analysis showed increased thermal stability of samples filled with nanoparticles. An attractive interaction between boehmite and CEOS matrix influenced the curing. Real-time infrared spectroscopy (RT-IR) experiments demonstrated that the epoxide conversion rate of nanocomposites was slightly increased compared to neat resin. The beneficial role of the BA can be explained by the participation of hydroxyl groups at the particle surface in photopolymerization processes and by the complementary contribution of p-toluenesulfonic acid surface modifier and water molecules introduced into the system with nanoparticles.

Nonhydrolytic sol–gel synthesized oligosiloxane resin reinforced thiol-ene photocured coatings for the immobilization of acetylcholinesterase

Acetylcholinesterase (AChE), which is responsible for the hydrolysis of neurotransmitter acetylcholine, is a critical enzyme for the nervous system and also a biomarker for organophosphorous pesticide detection. The immobilization of AChE is an active area of research and recently the use of sol–gel-derived materials for enzyme immobilization has gained a lot of attraction. In this work, AChE was covalently immobilized onto a photocured substrate which was reinforced with an oligosiloxane resin. The oligosiloxane resin was designed to have both vinyl and epoxide groups and prepared via nonhydrolytic sol–gel technique. The strategy employed in this study offered a platform that has good mechanical and thermal properties and also suitable for modification. Thus, AChE was also immobilized onto these substrates after amine modification of the epoxy groups and followed by glutaraldehyde activation. Over 80% enzyme immobilization yield was achieved. At certain pH values (5.5 and 8.5) and under relatively higher temperatures (above 40 °C) the immobilized enzymes were found to have higher catalytic activity than the free enzyme. Furthermore, by immobilization the reuse and the storage stability of the enzyme was improved and the stability of the immobilized enzyme against the inhibitory effects of certain metal cations was enhanced.

Siloxane-Encapsulated Upconversion Nanoparticle Hybrid Composite with Highly Stable Photoluminescence against Heat and Moisture.

Herein, we report a siloxane-encapsulated upconversion nanoparticle hybrid composite (SE-UCNP), which exhibits excellent photoluminescence (PL) stability for over 40 days even at an elevated temperature, in high humidity, and in harsh chemicals. The SE-UCNP is synthesized through UV-induced free-radical polymerization of a sol-gel-derived UCNP-containing oligosiloxane resin (UCNP-oligosiloxane). The siloxane matrix with a random network structure by Si-O-Si bonds successfully encapsulates the UCNPs with chemical linkages between the siloxane matrix and organic ligands on UCNPs. This encapsulation results in surface passivation retaining the intrinsic fluorescent properties of UCNPs under severe conditions (e.g., 85 °C/85% relative humidity) and a wide range of pH (from 1 to 14). As an application example, we fabricate a two-color binary microbarcode based on SE-UCNP via a low-cost transfer printing process. Under near-infrared irradiation, the binary sequences in our barcode are readable enough to identify objects using a mobile phone camera. The hybridization of UCNPs with a siloxane matrix provides the capacity for highly stable UCNP-based applications in real environments.

The Synthesis and Morphology of a Perfluoroalkyl Oligosiloxane@SiO2 Resin and Its Performance in Anti-Fingerprint Coating

In order to improve the hydro- and oleo-phobic properties of anti-fingerprint coating, novel oligosiloxane intermediate bearing perfluorodecyl/octyl and triethoxy silylethylene groups were synthesized; then, a series of nano-hybrid perfluoroalkyl oligosiloxane resins (FSi@SiO2) were synthesized using the hydrolysis and condensation of FVPS with tetraethylorthosilicate. The chemical structure, morphology, and performance of FSi@SiO2 were investigated. The results indicate that the FSi@SiO2 is a nano hybrid fluorinated polysiloxane resin with mean particle sizes of 200–400 nm. And under nanoparticles and perfluoroalkyl groups bonded in the resin, FSi@SiO2 not only showed a micro rough morphology in atomic force microscopy observation but also could provide the treated substrates with excellent hydro- and oleo-phobicity. As a result, the water and oil contact angles reached 120.3° and 87.5° on the treated glass, respectively; meanwhile, fingerprints were easily cleaned without any stains.

A robust transparent protective hard-coating material using physicochemically-incorporated silica nanoparticles and organosiloxanes

Abstract Here, we report on the synthesis of a silica nanoparticle (NP)-reinforced oligosiloxane nanohybrid material (SM-nanocomposite) and demonstrate its properties as a robust transparent hard coating material for various applications. The oligosiloxane (MMO) resin as a matrix was synthesized using methyl and methacryl silanes via a hydrolytic sol-gel condensation. The silica NPs with various sizes (12, 20 and 60 nm) as nanofillers were also synthesized through a hydrolytic sol-gel condensation, and the surface of NPs was organically modified with methyl and methacryl functions, which allowed stable dispersion and chemical cross-linking of the NPs with MMO matrix. In this work, we introduce synthetic steps of the nanocomposite and discuss the optical, morphological, thermal and mechanical properties of the composite.

Synthesis and characterization of hysteresis-free zirconium oligosiloxane hybrid materials for organic thin film transistors

Zirconium oligosiloxane resin was synthesized by a sol-gel reaction and UV-curing for organic thin film transistors (OTFTs) application. The synthesized resin has long-term stability and durability, which could be easily processed to produce a smooth coating on Si substrate. The dielectric constant of the film increased from 2.46 to 4.67 according to the variation of zirconium content. In addition, a low leakage current density of 10−6–10−7A/cm2 at 2MV/cm was obtained. Pentacene-based OTFTs were fabricated using the synthesized hybrimer as the gate dielectric layer, and their performances were optimized by tuning the ratio of zirconium and siloxane. Organic thin film transistors with zirconium oligosiloxane gate insulator were found to exhibit excellent performances with enhanced mobility at low applied voltage, a high on/off ratio, and nearly-hysteresis-free transfer characteristics.

Quantum Dot/Siloxane Composite Film Exceptionally Stable against Oxidation under Heat and Moisture.

We report on the fabrication of a siloxane-encapsulated quantum dot (QD) film (QD-silox film), which exhibits stable emission intensity for over 1 month even at elevated temperature and humidity. QD-silox films are solidified via free radical addition reaction between oligosiloxane resin and ligand molecules on QDs. We prepare the QD-oligosiloxane resin by sol-gel condensation reaction of silane precursors with QDs blended in the precursor solution, forgoing ligand-exchange of QDs. The resulting QD-oligosiloxane resin remains optically clear after 40 days of storage, in contrast to other QD-containing resins which turn turbid and ultimately form sediments. QDs also disperse uniformly in the QD-silox film, whose photoluminescence (PL) quantum yield (QY) remains nearly unaltered under harsh conditions; for example, 85 °C/5% relative humidity (RH), 85 °C/85% RH, strongly acidic, and strongly basic environments for 40 days. The QD-silox film appears to remain equally emissive even after being immersed into boiling water (100 °C). Interestingly, the PL QY of the QD-silox film noticeably increases when the film is exposed to a moist environment, which opens a new, facile avenue to curing dimmed QD-containing films. Given its excellent stability, we envision that the QD-silox film is best suited in display applications, particularly as a PL-type down-conversion layer.

Transparent, thermally stable methyl siloxane hybrid materials using sol-gel synthesized vinyl-methyl oligosiloxane resin

Vinyl-methyl oligosiloxane resin was synthesized by a hydrolytic sol-gel reaction of vinyltriethoxysilane and dimethyldiethoxysilane. Hydrochloric acid was added as a catalyst to promote the hydrolysis of silane monomers to form a highly condensed siloxane resin (Condensation degree = 95 %). The vinyl-methyl oligosiloxane and hydrogen-methyl oligosiloxane resin was then cured by a thermal hydrosilylation reaction with a minimal platinum catalyst content (3 ppm). The increased cross-linking density improved the thermal decomposition temperature and lowered the weight loss at a high temperature. The fabricated methyl-siloxane hybrid material (hybrimer) shows superior thermal stability (decomposition temperature >530 °C), good long-term thermal resistance (300 °C, 20 h) and transparency (92 % at 450 nm, 83 % at 350 nm) in the visible and ultraviolet ranges. Based on these characteristics, the methyl-siloxane hybrimer can be applied to various applications, including thermally stable optical materials.

Preparation and Evaluation of a Zirconia/Oligosiloxane Nanocomposite for LED Encapsulation.

A zirconia/oligosiloxane nanocomposite encapsulant has been developed and tested in a high-power LED package against commercial silicone resins. The composite was a marriage of zirconia nanocrystals modified with butyric acid (BA) and 3-methacryloxy propyl trimethoxysilane (MPTMS) and a high-index methacryloxy-oligosiloxanes resin made from MPTMS plus dimethyl, diphenyl, and triphenyl silanes. The modified zirconia had an index of 1.762 (@589 nm) and was dispersible in many solvents. The oligosiloxane resin, however, had an index of 1.5413 with good encapsulation properties and low viscosity allowing the incorporation of more zirconia. The final nanocomposite showed a refractive index of 1.625 with high transparency and a wavelength-independent scattering, both desirable for the light extraction from LED. When tested in a high-power LED package, the composite encapsulant resulted in 13% more light output compared to the commercial encapsulant (OE-6630, Dow Corning Corp.) and showed longer than 1000 h of lifetime (L70) under the steady-state Temperature Humidity Bias (THB) test.

Optically recoverable, deep ultraviolet (UV) stable and transparent sol–gel fluoro siloxane hybrid material for a UV LED encapsulant

A UV transparent and stable fluoro-siloxane hybrid material was prepared for a deep UV-LED encapsulant. The hybrimer was fabricated by hydrosilylation reaction of vinyl-fluoro oligosiloxane resin.

Ultraviolet light stable and transparent sol-gel methyl siloxane hybrid material for UV light-emitting diode (UV LED) encapsulant.

An ultraviolet (UV) transparent and stable methyl-siloxane hybrid material was prepared by a facile sol-gel method. The transparency and stability of a UV-LED encapsulant is an important issue because it affects UV light extraction efficiency and long-term reliability. We introduced a novel concept for UV-LED encapsulation using a thermally curable oligosiloxane resin. The encapsulant was fabricated by a hydrosilylation of hydrogen-methyl oligosiloxane resin and vinyl-methyl siloxane resin, and showed a comparable transmittance to polydimethylsiloxane (PDMS) in the UVB (∼300 nm) region. Most remarkably, the methyl-siloxane hybrid materials exhibited long-term UV stability under light soaking in UVB (∼300 nm) for 1000 h.

Low temperature curable epoxy siloxane hybrid materials for LED encapsulant

ABSTRACTA thermally cured epoxy‐siloxane hybrid material that is curable at low temperature (L‐expoxy hybrimer) was investigated for use as an LED encapsulant. This new hybrimer was fabricated using thermally initiated, cationic polymerization of cycloaliphatic epoxy oligosiloxane (CAEO) resin, derived from non‐hydrolytic sol–gel, mixed with oxetane hardener in the presence of a hexafluoroantimonate‐type thermo‐cationic initiator. The L‐epoxy hybrimer was cured at a lower temperature (below 120°C) than previously reported for an epoxy hybrimer with anhydride hardener (above 180°C). The L‐epoxy hybrimer showed high thermal resistance to yellowing under long‐term high temperature condition, and maintained good optical transmittance. Also, it had a high refractive index (up to 1.57), as well as the hardness (Shore D 80), and low water‐vapor permeability, when the new hybrimer was used to encapsulate an LED, it showed good adhesion without cracks or delamination and maintained their initial performance after the long‐term aging tests (120 and 85°C at 85% humidity). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39968.

Sol–gel synthesized linear oligosiloxane-based hybrid material for a thermally-resistant light emitting diode (LED) encapsulant

The thermal resistance against discoloration of a high refractive index phenyl-siloxane hybrid material (hybrimer) was studied for LED encapsulation. The phenyl hybrimer was fabricated by a hydrosilylation reaction of linearly-structured vinyl oligosiloxane and hydrogen oligosiloxane resins using a platinum (Pt) catalyst. The linear oligosilxane resins were synthesized by a non-hydrolytic sol–gel condensation reaction of di-functional silane precursors, containing vinyl, hydrogen, and phenyl groups. The oligosiloxane, having a higher degree of condensation and molecular size compared with the branched oligosiloxane, provided low shrinkage and an effective curing behavior. The phenyl hybrimer showed high optical transparency and a refractive index of up to 1.57. In particular, the amount of Pt catalyst was minimized to inhibit yellowing of the hybrimer under long-term aging at 180 °C. These results suggest that the linear oligosiloxane-derived phenyl hybrimer could be used as a high performance LED encapsulant.

High performance encapsulant for light-emitting diodes (LEDs) by a sol–gel derived hydrogen siloxane hybrid

The hydrosilylation reaction is a dominant curing method for the light-emitting diode (LED) silicone encapsulant, which requires characteristics of high transparency, high refractive index, and thermal stability against the LED junction temperature. In this research, we synthesized a hydrogen containing oligosiloxane resin through non-hydrolytic sol–gel condensation. Methyldiethoxysilane (MDES) and diphenylsilanediol (DPSD) were used as precursors and a non-hydrolytic sol–gel condensation reaction was performed under acidic conditions. The synthesized hydrogen oligosiloxane resin was mixed with a phenyl and vinyl containing oligosiloxane (PVO) resin, which was prepared by a sol–gel condensation between vinyltrimethoxysilane (VTMS) and the DPSD. This blended solution was cured at 150 °C for 4 hours to complete the hydrosilylation reaction. The cured material (phenyl hybrimer) shows low shrinkage during the curing reaction and provides excellent transparency (∼90% at 450 nm) and thermal stability (440 °C) with a high refractive index (n = 1.58 at 632.8 nm).

Cycloaliphatic epoxy oligosiloxane‐derived hybrid materials for a high‐refractive index LED encapsulant

AbstractCycloaliphatic epoxy oligosiloxane resins with a high degree of condensation (>85%) were synthesized by a nonhydrolytic sol–gel reaction using 2‐(3,4‐epoxycyclohexyl)ethyltrimethoxysilane (ECTS), diphenylsilanediol (DPSD), and triphenylsilanol (TPS). Cycloaliphatic epoxy hybrimers with 2 mm thickness fabricated by thermal curing of cycloaliphatic epoxy oligosiloxane resins with a hardener and catalyst were optically transparent (∼90%) with a high refractive index of up to 1.583. The fabricated hybrimers also show high thermal resistance having no yellowing during thermal aging at 120°C for 1008 h and a high decomposition temperature (>300°C). On the strengths of these characteristics, the hybrimers are expected to find application as LED encapsulants. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

High performance organic-inorganic hybrid barrier coating for encapsulation of OLEDs

UV curable cycloaliphatic epoxy functionalized oligosiloxane resin is synthesized by non-hydrolytic sol–gel reaction for application in encapsulation of organic light emitting devices (OLEDs). The physical and chemical properties of polymerized cycloaliphatic epoxy hybrid materials (hybrimers) are easily tunable by controlling the precursors. A single hybrimer coating on a PET film is optically transparent and shows low permeability of up to 0.68 g m−2 day−1 per mil measured by a Ca degradation test. It is found that the permeability is influenced by the siloxane and epoxy network density, and the surface energy of the coating. An optimized hybrimer barrier coated film is applied to the encapsulation of an OLED with the aim of extending life-time.

Thermal resistance of cycloaliphatic epoxy hybrimer based on sol‐gel derived oligosiloxane for LED encapsulation

AbstractCycloaliphatic epoxy hybrimer bulk was successfully fabricated by thermal curing of cycloaliphatic epoxy oligosiloxane resin synthesized by a sol‐gel condensation reaction with methylhexahydrophthalic anhydride (MHHPA) and tetrabutylphosphonium methanesulfonate (TBPM). The composition of MHHPA and TBPM in the resin was optimized to minimize yellowness of the cycloaliphatic epoxy hybrimer bulk. The sample with the optimized composition showed little discoloration upon thermal aging at 120°C for 360 h under an air atmosphere. On the basis of its high thermal stability with appropriate hardness and a high refractive index of 1.55, cycloaliphatic epoxy hybrimer bulk can be used as a LED encapsulant for white LEDs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010