Epoxycyclohexyl Polyhedral Oligomeric Silsesquioxanes Research Articles

Low defect and high mechanical properties POSS copolymerization phthalonitrile resin prepared by powder hot isostatic pressing

The high melting point of high-temperature resistant phthalonitrile resin is often prone to defects in traditional hot melt manufacturing. And its high cross-linking density leads to poor toughness of the resin. In this work, we report for the first time a novel densifying processing, powder hot isostatic pressing (PHIP), for phthalonitrile resin with low defect and high mechanical performance. The bending strength and impact strength of the pure phthalonitrile resin (PBAPN) by PHIP reached to 108.5 MPa and 9.1 kJ·m−2, respectively, increasing by 186.3% and 405.6% than PBAPN by hot melt method. The epoxycyclohexyl polyhedral oligomeric silsesquioxane (EP-POSS) with excellent heat resistance was used to achieve synchronous improvement of thermal and mechanical properties of phthalonitrile resin. The bending strength and impact strength of the phthalonitrile resin containing 1 wt% POSS (PBAPNPOSS-1) further increased to 120.1 MPa and 13.0 kJ·m−2. In addition, the glass transition temperature of PBAPNPOSS-5 increased by 40 °C compared with PBAPN.

Multifunctional Properties of Polyhedral Oligomeric Silsesquioxanes (POSS)-Based Epoxy Nanocomposites.

In this study, a tetrafunctional epoxy resin was loaded with 5 wt% of three different types of polyhedral oligomeric silsesquioxane (POSS) compounds, namely, DodecaPhenyl POSS (DPHPOSS), Epoxycyclohexyl POSS (ECPOSS), Glycidyl POSS (GPOSS), and 0.5 wt% of multi-walled carbon nanotubes (CNTs) in order to formulate multifunctional structural nanocomposites tailored for aeronautic and aerospace applications. This work aims to demonstrate how the skillful combination of desired properties, such as good electrical, flame-retardant, mechanical, and thermal properties, is obtainable thanks to the advantages connected with nanoscale incorporations of nanosized CNTs with POSS. The special hydrogen bonding-based intermolecular interactions between the nanofillers have proved to be strategic in imparting multifunctionality to the nanohybrids. All multifunctional formulations are characterized by a Tg centered at values close to 260 °C, fully satisfying structural requirements. Infrared spectroscopy and thermal analysis confirm the presence of a cross-linked structure characterized by a high curing degree of up to 94% and high thermal stability. Tunneling atomic force microscopy (TUNA) allows to detect the map of the electrical pathways at the nanoscale of the multifunctional samples, highlighting a good dispersion of the carbon nanotubes within the epoxy resin. The combined action of POSS with CNTs has allowed to obtain the highest values of self-healing efficiency if compared to those measured for samples containing only POSS in the absence of CNTs.

Improvement of DC Breakdown Strength of the Epoxy/POSS Nanocomposite by Tailoring Interfacial Electron Trap Characteristics.

To date, breakdown voltage is an underlying risk to the epoxy-based electrical high voltage (HV) equipment. To improve the breakdown strength of epoxy resin and to explore the formation of charge traps, in this study, two types of polyhedral oligomeric silsesquioxane (POSS) fillers are doped into epoxy resin. The breakdown voltage test is performed to investigate the breakdown strength of neat epoxy and epoxy/POSS composites. Electron traps that play an important role in breakdown strength are characterized by thermally stimulated depolarized current (TSDC) measurement. A quantum chemical calculation tool identifies the source of traps. It is found that adding octa-glycidyl POSS (OG-POSS) to epoxy enhances the breakdown strength than that of neat epoxy and epoxycyclohexyl POSS (ECH-POSS) incorporated epoxy. Moreover, side groups of OG-POSS possess higher electron affinity (EA) and large electronegativity that introduces deep-level traps into epoxy resin and restrain the electron transport. In this work, the origin of traps has been investigated by the simulation method. It is revealed that the functional properties of POSS side group can tailor an extensive network of deep traps in the interfacial region with epoxy and enhance the breakdown strength of the epoxy/POSS nanocomposite.

A low-shrinkage dental composite with epoxy-polyhedral oligomeric silsesquioxane

Polymerization shrinkage and mechanical properties affect the service life of dental restorative composites. Polyhedral oligomeric silsesquioxanes (POSS) can be an efficient strategy to improve the shrinkage properties and mechanical properties simultaneously. In this work, epoxycyclohexyl POSS (E-POSS) was used to modify the Bis-GMA/TEGDMA dental resins. E-POSS were introduced into the acrylic resin system via ring-opening reaction, and a cationic/free radical hybrid system was obtained. Double bond conversion, glass transition temperature, heterogeneity, crosslink density of dental resins and volumetric shrinkage, water sorption/solubility, flexural strength/modulus of dental composites were investigated. As the introduction of E-POSS caused higher double bond conversion and lower crosslink density, the polymerization shrinkage was significantly reduced to 2.91% (p < 0.05) and the flexural strength increased to 117.19 MPa (p < 0.05) compared to the control sample (5.06%, 99.16 MPa, p<0.05). Lower water sorption and solubility were also observed in composites contained E-POSS (p < 0.05).

Femtosecond Laser Direct Writing of 3D Silica‐like Microstructure from Hybrid Epoxy Cyclohexyl POSS

AbstractGiven the importance of epoxy cyclohexyl polyhedral oligomeric silsesquioxane (epoxy‐POSS) as a silica‐like hybrid material of optical clarity, high thermal and mechanic stability, the two‐photon initiated polymerization of epoxy‐POSS using diphenyliodonium hexafluorophosphate as photoacid generators for UV lithography and femtosecond laser direct writing is studied. The hybrid resist exhibits high thermal stability: decomposition temperatures are found at ≈350 and 400 °C when calcined in air and argon, respectively. The corresponding calcined products are found as silica‐like structures with chemical formulas of C1.5SiO3.5 and C5SiO3, evidenced by energy dispersive X‐ray analysis (EDX), fourier‐transform infrared spectroscopy (FTIR), and elemental analysis. An equation regarding the two‐photon polymerized line width as functions of intensity of laser (Plaser) and scanning speed (V) is proposed in describing the effect of Gaussian light on polymerized lines. Experimental verification of the equation is given to prove a nonlinear optical process. Line width with a resolution of 250 nm is achieved on a glass substrate, while the resolution is 400 nm when fabricated on a silicon wafer. 3D structured woodpiles are fabricated and show no volumetric shrinkage upon 300 °C calcination in air environment, demonstrating a high thermal stability.

Cure Behavior and Thermomechanical Properties of Phthalonitrile⁻Polyhedral Oligomeric Silsesquioxane Copolymers.

Phthalonitrile–polyhedral oligomeric silsesquioxane (POSS) copolymers were prepared by adding two different POSS cage mixtures: epoxycyclohexyl POSS (EP0408) and N-phenylaminopropyl POSS (AM0281). The cure behavior and properties of these polymers were analyzed and compared using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), Fourier transform far infrared (FTIR) measurements, and rheometric studies. The POSS-containing polymers showed higher chemical reactivity, better thermal stability and better mechanical performance in comparison to their unmodified counterparts. All the polymers showed water absorption below 1.5%. As revealed by FTIR measurements, the polymerization products contained triazine ring structures that were responsible for the superior thermal properties exhibited by these POSS-containing polymers.

The grafting reaction of epoxycyclohexyl polyhedral oligomeric silsesquioxanes with carboxylic methoxypolyethylene glycols and the properties of composite solid polymer electrolytes with the graftomer

ABSTRACTA novel organic–inorganic hybrid of epoxycyclohexyl polyhedral oligomeric silsesquioxane (e‐POSS)–grafted carboxylic methoxypolyethylene glycols (mPEG‐COOH), that is, a POSS‐mPEG graftomer, was synthesized. The grafting reaction of e‐POSS and mPEG‐COOH was characterized by Fourier transform infrared (FTIR) and 1H‐NMR spectroscopy. Then the graftomer was used to develop new composite solid polymer electrolyte (SPE) films with a carboxylated nitrile rubber–epoxidized natural rubber (XNBR‐ENR) self‐crosslinked blend system as a dual‐phase polymer matrix. The self‐crosslinked reaction of the XNBR‐ENR matrix was investigated using ATR‐FTIR. The morphology of the SPE films and the distribution of lithium salt were investigated using field emission scanning electron microscopy and X‐ray diffraction, and the result illustrated that the addition of POSS‐mPEG could promote and accelerate the dissociation of LiClO4. The best effect within the range of this study was achieved when 25 phr POSS‐mPEG was involved. The differential scanning calorimetry analysis proved that the glass‐transition temperature of the composite SPE films was reduced with the increase of POSS‐mPEG. The ionic conductivity of the composite SPE films was investigated by electrochemical impedance spectroscopy. The highest ionic conductivity in this study of 2.57 × 10−5 S cm−1 was obtained with 25 phr POSS‐mPEG loading. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44460.

Crystalline, Thermal, and Biodegradable Properties of Poly(L-Lactic Acid)/Poly(D-Lactic Acid)/POSS Melt Blends

ABSTRACTA ternary nanocomposite consisting of poly(L-lactic acid) (PLLA), poly(D-lactic acid) (PDLA), and epoxy cyclohexyl polyhedral oligomeric silsesquioxane (e-POSS) was prepared by reactive blending method. Scanning electron microscopy revealed that the feeding of three compositions in batches, i.e., PDLA incorporation at different times, was more beneficial for the even dispersion of POSS in matrix. POSS introduction improved the homocrystallinity and stereocomplex of the blends. Rheological properties and heat resistance were enhanced, which indicated potential extensive application of PLLA-based materials. The optimization of degradation stability in saline buffer was attributed to the various hydrophobic properties of blends caused by POSS structure.

Study on properties of gel polymer electrolytes based on ionic liquid and amine‐terminated butadiene‐acrylonitrile copolymer chemically crosslinked by polyhedral oligomeric silsesquioxane

AbstractBased on amine‐terminated butadiene‐acrylonitrile copolymer chemically crosslinked by epoxycyclohexyl polyhedral oligomeric silsesquioxane (POSS), a novel gel polymer electrolyte (GPE) were prepared by introducing one ionic liquid and LiClO4 into the polymer framework. Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and X‐ray diffraction analysis confirmed the interaction between the ionic liquid and LiClO4, and this interaction contributes to dissolving LiClO4 salt and increasing the ionic conductivity of GPE. Less content of POSS leads to higher ionic conductivities but lower gel content and modulus. The maximum ionic conductivity of 2.0 × 10−4 S cm−1 (30°C) was achieved and an Arrhenius‐type relationship between ionic conductivities and temperatures could be detected over the investigated temperature range. The generated GPE exhibited good electrochemical stability to 4 V from cyclic voltammogram tests, which made this kind of GPE a promising candidate for rechargeable lithium batteries. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effect of the epoxycyclohexyl polyhedral oligomeric silsesquioxane content on the dynamic fragility of an epoxy resin

This study aims to evaluate the performance of epoxy/epoxycyclohexyl polyhedral oligomeric silsesquioxane nanocomposites focusing on differential scanning calorimetry and dynamic mechanical analysis. Nanocomposites with distinct nanoreinforcement contents (1, 2 and 5wt.%) were studied. Using differential scanning calorimetry and dynamic mechanical analyses it was possible to assess some properties based on well-established concepts and correlate them with the structure formed. It was observed that the glass transition temperature decreases following the incorporation of epoxycyclohexyl polyhedral oligomeric silsesquioxane, indicating, in principle, that there is more mobility in the new system formed. However, other calculated parameters (cooperative rearrangement region, Angell fragility and Kauzmann temperature) showed no trend as a result of epoxycyclohexyl polyhedral oligomeric silsesquioxane incorporation.

A study on the curing kinetics of epoxycyclohexyl polyhedral oligomeric silsesquioxanes and hydrogenated carboxylated nitrile rubber by dynamic differential scanning calorimetry

AbstractA new organic–inorganic hybrid material was prepared through reactive blending of hydrogenated carboxylated nitrile rubber (HXNBR) with epoxycyclohexyl polyhedral oligomeric silsesquioxanes (epoxycyclohexyl POSS). The structure of the composite was characterized by Fourier transform infrared spectroscopy (FTIR) and solid‐state 13C Nuclear Magnetic Resonance spectra (solid‐state 13C‐NMR). The differential scanning calorimetry (DSC) at different heating rates was conducted to investigate the curing kinetics. A single overall curing process by an nth‐order function (1 − α)n was considered, and multiple‐heating‐rate models (Kissinger, Flynn–Wall–Ozawa, and Crane methods) and the single‐heating‐rate model were employed. The apparent activation energy (Ea) obtained showed dependence on the POSS content and the heating rate (β). The overall reaction order n was practically constant and close to 1. The isoconversion Flynn–Wall–Ozawa method was also performed and fit well in the study. With the single‐heating‐rate model, the average Ea for the compound with a certain POSS content, 66.90–104.13 kJ/mol was greater than that obtained with Kissinger and Flynn–Wall–Ozawa methods. Furthermore, the calculated reaction rate (dα/dt) versus temperature curves fit with the experimental data. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Curing reactions and properties of organic–inorganic composites from hydrogenated carboxylated nitrile rubber and epoxycyclohexyl polyhedral oligomeric silsesquioxanes

AbstractNovel organic–inorganic composites were prepared by curing hydrogenated carboxylated nitrile rubber (HXNBR) with epoxycyclohexyl polyhedral oligomeric silsesquioxanes (POSS) through chemical bonding of carboxyl groups of HXNBR and epoxy groups of POSS. The process of the curing reaction was investigated using in situ Fourier transform infrared spectroscopy. The reaction order, the activation energy and the frequency factor were obtained through a kinetic analysis using differential scanning calorimetry. Through dynamic mechanical analysis, the glass transition temperature, crosslink density and degree of heterogeneity of the composites were estimated, and they showed an increasing tendency with increasing POSS content. The results of dielectric property measurements showed that the dielectric constant of the composites decreased with increasing POSS content in the studied frequency range. Copyright © 2010 Society of Chemical Industry

Imprint lithography enabling ultra-low loss coaxial interconnects

Processing techniques have been demonstrated to fabricate a novel structure with smooth transitions, metallic shielding, and encapsulated air dielectric layers using sacrificial polymers and the three-dimensional patterning capabilities of imprint lithography. This innovative structure incorporates encapsulated air dielectrics with copper shielding. A semicircular stamp was fabricated to create the circular base of the coaxial transmission line using the reflow properties of solder, and imprinting the stamp produced smooth rounded terminations. Copper shielding was electroplated and a sacrificial photosensitive polycarbonate was patterned using a unique interaction with the copper. The polycarbonate was over-coated with a epoxycyclohexyl polyhedral oligomeric silsesquioxane (POSS) layer and then thermally decomposed to form an air cavity. A center conductor was patterned using photolithography and electro-deposition. The half-coaxial line was aligned with a sample with the top portion of the copper shielding and bonded in the imprinter to complete the structure. Imprint lithography also demonstrated the capability to planarize surfaces which simplified the buildup process, and complex structures were fabricated with a comparable number of registration steps to traditional transmission lines. The mechanical integrity of the air-clad transmission lines was also evaluated using nano-indentation.

Photodefinable Epoxycyclohexyl Polyhedral Oligomeric Silsesquioxane

A photodefinable dielectric was developed using epoxycyclohexyl polyhedral oligomeric silsesquioxanes (POSS) and a photocatalyst. POSS is a hybrid organic/inorganic dielectric which has favorable mechanical and chemical stability for use as a permanent dielectric in microfabrication. Sharp, 10 μm wide features were formed from POSS using 365 nm radiation. The optical contrast was 1.51. POSS films were thermally stable to 350°C and demonstrated chemical stability in a variety of solvents and oxidants. The polymer film had an elastic modulus of 5.3 GPa and a hardness of 0.64 GPa. The POSS had high etch selectivity compared with organic films for pattern transfer.

Effect of POSS on morphology and properties of poly(2,6-dimethyl-1,4-phenylene oxide)/polyamide 6 blends

Poly(2,6-dimethyl-1,4-phenylene oxide)/polyamide 6 (PPO/PA6) (50/50 w) blends filled with epoxycyclohexyl polyhedral oligomeric silsesquioxane (POSS) were prepared via melt-mixing. The reactions between POSS and PPO/PA6 blends were studied by Fourier transform infrared spectroscopy, end group and gel content tests. The morphology of PPO/PA6/POSS composites was observed by field emission scanning electron microscope and transmission electron microscope. As a chain extender and a crosslinking agent for PA6, POSS largely affected the morphology of the composites, which was mainly dependent on the melt-viscosity ratio and interfacial tension between the components. With increasing POSS content from 2 to 4 phr, the morphology of the composites transformed from droplet/matrix to co-continuous morphology. The PPO/PA6/POSS composites with co-continuous morphology had the better mechanical properties than those with droplet/matrix morphology. Dynamic mechanical thermal analysis showed that the addition of POSS increased the T g of PA6.

Properties of poly(butylene terephthalate) chain‐extended by epoxycyclohexyl polyhedral oligomeric silsesquioxane

AbstractEpoxycyclohexyl polyhedral oligomeric silsesquioxane (epoxy–POSS) was used to prepare a chain‐extended poly(butylene terephthalate) (PBT) with a twin‐screw extruder. The effect of epoxy–POSS on the melt flow index, mechanical properties, rheological behavior, and thermal properties of chain‐extended PBT was investigated. PBT had an intrinsic viscosity of 1.1 dL/g and a carboxy1 content of 21.6 equiv/106 g, but the PBT chain‐extended with 2 wt % epoxy–POSS had an intrinsic viscosity of 1.7 dL/g and a carboxy1 content lower than 7 equiv/106 g. After the addition of epoxy–POSS, the melt flow index of PBT dramatically decreased, the elongation at break increased greatly, the tensile strength increased slightly, and the thermal stability was also improved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008