Use Of Polyhedral Oligomeric Silsesquioxane Research Articles

Redox‐Active Organic Molecules Supported by Polyhedral Oligomeric Silsesquioxane

AbstractOrganic redox molecules have attracted considerable attention because of their abundant availability and excellent design flexibility. For practical applications, these molecules must be anchored onto scaffolds such as polymers to prevent crystallization and elution into the electrolyte. In this study, we explore the use of polyhedral oligomeric silsesquioxane (POSS) derivatives as scaffolds for anthraquinone (AQ) and hydroquinone. We investigated the cage structure of POSS and the number of redox units incorporated. Notably, a corner‐opened POSS (CO‐POSS) variant with three AQ units exhibited reversible redox behavior under neutral, acidic, and basic conditions. Furthermore, we examined the air‐battery performance of AQ‐modified CO‐POSS as an anode‐active material.

Use of Polyhedral Oligomeric Silsesquioxane (POSS) in Drug Delivery, Photodynamic Therapy and Bioimaging.

Polyhedral oligomeric silsesquioxanes (POSS) have attracted considerable attention in the design of novel organic-inorganic hybrid materials with high performance capabilities. Features such as their well-defined nanoscale structure, chemical tunability, and biocompatibility make POSS an ideal building block to fabricate hybrid materials for biomedical applications. This review highlights recent advances in the application of POSS-based hybrid materials, with particular emphasis on drug delivery, photodynamic therapy and bioimaging. The design and synthesis of POSS-based materials is described, along with the current methods for controlling their chemical functionalization for biomedical applications. We summarize the advantages of using POSS for several drug delivery applications. We also describe the current progress on using POSS-based materials to improve photodynamic therapies. The use of POSS for delivery of contrast agents or as a passivating agent for nanoprobes is also summarized. We envision that POSS-based hybrid materials have great potential for a variety of biomedical applications including drug delivery, photodynamic therapy and bioimaging.

Solid cross linked-poly(ethylene oxide) electrolyte gate dielectrics for organic thin-film transistors

Solid polymer electrolyte gate dielectric based on cross-linked poly(ethylene oxide) (CPEO) was developed and employed for organic thin-film transistors (OTFTs). Mechanical stability, high areal capacitance, and amorphous morphology of CPEO were achieved via the use of polyhedral oligomeric silsesquioxane (POSS) as cross-linker, dissolved ion [EMIM][TFSI] as electrolyte, and PEO with low molecular weight as polymer matrix, respectively. The resulting solid polymer electrolyte showed excellent insulating properties with low leakage current density (1.8×10−7Acm−2 at 1V) and high capacitance per area (∼ 1μFcm−2 at 100Hz). Furthermore, dielectric properties of the developed polymer electrolytes including ionic conductivity as well as segmental relaxation time were investigated. The polyelectrolyte dielectric was employed for bottom-gate/top-contact organic thin-film transistors and the resulting devices showed decent electrical performance with a carrier mobility of 0.12 (±0.03)cm2V−1s−1 and a current on/off ratio of 103 at low operating voltage of 5V.

Polyhedral oligomeric silsesquioxane/epoxy coatings: a review

Nowadays, there is a need for a paradigm shift in material selection for surface coatings so as to meet the requirements of advanced systems. Polyhedral oligomeric silsesquioxanes (POSS) are three-dimensional networks with a silica-like core covered by an organic shell, a promising nanosized structure for organic coatings. The use of POSS structures in coating materials has experienced an almost erratic period over the past decade, mainly because of the synthesis of POSS being exclusive and, to some extent, expressive. However, there has been a big return to the use of POSS in coatings during the last years. Epoxy is best known for its versatility of usage as an organic coating. Hybrid organic–inorganic POSS nanostructures with unique properties are a complement to the epoxy for coating applications. The tailorable compatibility and considerable reactivity of POSS molecules towards organic groups have made them promising candidates for emerging multifunctional epoxy coatings. In this sense, the focus of this review is placed on POSS/epoxy nanocomposite coatings. The thermal, mechanical, anti-corrosion and dielectric properties of POSS/epoxy coatings have been comprehensively studied and discussed.

The Rediscovery of POSS: A Molecule Rather than a Filler.

The use of polyhedral oligomeric silsesquioxanes (POSSs) for making polymer composites has grown exponentially since the last few years of the 20th century. In comparison with the other most commonly used fillers, POSSs possess the advantage of being molecules. Thus, this allows us to combine their nano-sized cage structures, which have dimensions that are similar to those of most polymer segments and produce a particular and exclusive chemical composition. These characteristics linked with their hybrid (inorganic–organic) nature allow researchers to modify POSS according to particular needs or original ideas, before incorporating them into polymers. In this present study, we first start with a brief introduction about the reasons for the rediscovery of these nanoparticles over the last 25 years. Starting from the form of POSS that is most widely used in literature (octaisobutyl POSS), this present study aims to evaluate how the reduction of symmetry through the introduction of organic groups favors their dispersion in polystyrene matrix without compromising their solubility.

Evaluation of the Mechanic and Electrochemical Properties of an Epoxy Coating with Addition of Different Polyhedral Oligomeric Silsesquioxanes (POSS) Applied on Substrate of Low Alloy Steel

The epoxy resin is one of the matrices most employed in obtaining composites and coatings. Its properties have been modified using materials such as clays and polyhedral oligomeric silsesquioxanes - POSS. The use of POSS in the preparation of thermosetting nanocomposites has been studied in obtaining hybrid materials with higher mechanic and surface properties. The functionality of POSS cage is important, since a thermosetting is formed by a cross-linked structure that can interact at any direction, forming bonds or acting in the interface of the cages inserted. This works aims to evaluate the influence of three POSS (Glycidylisobutyl-POSS, Triglycidylisobutyl-POSS and Glycidyl-POSS) added in epoxy resin, in the mechanic and electrochemical behaviors, when applied on low alloy steel. It was observed an increase in roughness and hydrophobicity. The sample containing Glycidylisobutyl-POSS presented the best results of corrosion resistance. Glycidyl-POSS showed an inefficient dispersion, forming agglomerates, leading to a low electrochemical behavior.

유연한 디스플레이 소자의 보호막용 직접 패턴 형성이 가능한 POSS계 저유전 물질의 제조

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.

The Enhanced Encapsulation Capacity of Polyhedral Oligomeric Silsesquioxane‐based Copolymers for the Fabrication of Electrospun Core/Shell Fibers

This paper reports the use of polyhedral oligomeric silsesquioxane (POSS)-based copolymers to stabilize the core/shell interface for the facile fabrication of electrospun core/shell fibers. For the poly[(propylmethacryl-heptaisobutyl-polyhedral oligomeric silsesquioxane)-co-(methyl methacrylate)] (POSS-MMA)/poly(ε-caprolactone) (PCL) system, the bicontinuity of hybrid core/shell fibers can be tuned by controlling the phase separation of POSS-MMA/PCL in electrospinning solutions and therefore the size of PCL-in-POSS-MMA emulsion droplets. Our results demonstrate the enhanced encapsulation capacity of POSS-MMA copolymers as shell materials. Taking advantage of the rapid advancement of POSS-based copolymer synthesis, this study can potentially be generalized to guide the fabrication of various other POSS-based core/shell nano-/microstructures by using single-nozzle electrospinning or coaxial electrospinning.

Interaction in POSS-poly(ethylene-co-acrylic acid) nanocomposites

Use of polyhedral oligomeric silsesquioxane (POSS) in polymer-based nanocomposites is promising for the design of high-performance materials for several applications. In this study, nanocomposites based on ethylene-acrylic acid (EAA) copolymer and POSS molecules were prepared by melt mixing. In particular, partial cage POSS with different pendent organic groups was used to investigate the interaction between the –OH groups of POSS and the acrylic functionalities of the matrix. All nanocomposites were characterized by mechanical, rheological, thermal and spectroscopic analyses. In addition, PE-POSS compounds were prepared under the same processing conditions for sake of comparison. The POSS molecules affect the properties in the molten state and usually act as a plasticizer. However, this plasticizing effect should not be evident if the host polymeric matrix is able to interact with organosilicon molecules, in which case, the POSS molecules would confer an antiplasticizer effect. Therefore, all properties measured of EAA/POSS nanocomposites are the result of two contrasting phenomena, particularly the plasticizing and reinforcement effects. Moreover, the properties of these nanocomposites depend significantly on the presence of certain functionalities in the components and on possible interactions between them. Nanocomposites based on ethylene-acrylic acid copolymer (EAA) and polyhedral oligomeric silsesquioxanes (POSS) molecules were prepared by melt mixing: partial cage POSS with different pendent organic groups were used to investigate the interaction between the –OH POSS’s groups and the acrylic functionalities of the matrix. All measured properties of EAA/POSS nanocomposites are the result of two contrasting phenomena, particularly, the plasticizer and reinforcement effect. Moreover, the properties of up generation nanocomposites depend significantly on the presence of some functionalities in the components and on possible interaction between them.

Inorganic-Organic Hybrid Copolymers derived from Silsesquioxanes or Carborane Building Blocks

ABSTRACTTo explore competitive or cooperative effects novel organic-inorganic hybrid copolymers are being prepared and studied. The use of polyhedral oligomeric silsesquioxanes (POSS), a molecularly precise isotropic comonomer, is being utilized to take advantage of the inherent size scale of these particles, average diameters of 1-2 nm. The organic component selected for study in these hybrid systems are either semi-crystalline or amorphous polymers. The architectures of the hybrid copolymers range from random, to precise block copolymers, as well as telechelic and hemi-telechelic end-functionalized model compounds. The degree of POSS aggregation that occurs is found to be a function of thermal history, and processing conditions. Templating, or arresting, aggregation can be achieved using either crystalline organic polymer scaffolds in the bulk. The second inorganic comonomers for study has been constructed from icosahedral carboranes. Dicarbo-closo-decaboranes have been widely investigated for their thermal stability, chemical resistance, unique geometry, and the high cross-section for the capture of thermal neutrons. While carboranes have been widely incorporated into small molecules, metal complexes, and on a limited basis in polymer systems relatively little work exists relating their unique properties to systems with extended π-conjugation. Details of the syntheses, characterization and performance properties of both sets of hybrid systems will be discussed.

ChemInform Abstract: The Use of Polyhedral Oligomeric Silsesquioxane (POSS) as a Soluble Support for Organic Synthesis: A Case Study with a POSS‐Bound Isocyanate Scavenger Reagent.

AbstractThe use of POSS for the scavenging of hydrogen chloride allows the high‐yielding preparation of amides and a sulfonamide with high purity.

The use of polyhedral oligomeric silsesquioxane (POSS) as a soluble support for organic synthesis: A case study with a POSS-bound isocyanate scavenger reagent

The use of polyhedral oligomeric silsesquioxane (POSS) as a soluble support in organic synthesis is reported. A POSS-bound isocyanate was readily synthesised in one step from commercially available starting materials and was isolated in high yield and purity by simple filtration. It was found to perform well as a scavenger for excess amine in the solution phase synthesis of amides and sulfonamides, allowing product isolation in high yield and purity.

Polyhedral oligomeric silsesquioxane as a novel plasticizer for poly(vinyl chloride)

This study focuses on investigating the use of polyhedral oligomeric silsesquioxanes (POSS) to plasticize poly(vinyl chloride) (PVC). Conventional organic plasticizers for PVC, such as dioctyl phthalate (DOP), are somewhat volatile, leading to plasticizer loss and unwanted deterioration of the material properties over time. Previous experimental results indicate that methacryl-POSS, which is much less volatile due to its hybrid organic–inorganic structure, has the ability to plasticize PVC. Methacryl-POSS is miscible in the PVC only up to 15 wt%, thereby limiting its suitability as a plasticizer. However, through the use of ternary compositions it is possible to increase the proportion of methacryl-POSS in PVC substantially. The T g of appropriately formulated ternary PVC/POSS/DOP compounds can be reduced to near room temperature, and these materials exhibit desirable ductile behavior. Binary (PVC/DOP) and ternary (PVC/POSS/DOP) compounds formulated to the same T g values showed considerably different mechanical properties. Such findings reveal the possibility of using POSS to engineer the mechanical properties of plasticized PVC.