Preparation of Antifog Hard Coatings Based on Carboxy-Functionalized Polyhedral Oligomeric Silsesquioxane Cross-Linked with Oligo(ethylene glycol)s

In this study, we prepared antifog hard coatings by heating a mixture of carboxy-functionalized polyhedral oligomeric silsesquioxane (POSS-C) and oligo(ethylene glycol)s (OEGs, HO(CH2CH2O) n H, n = 1-6) in N,N-dimethylformamide, applying the mixture onto a glass substrate, and subsequently removing the solvent via heating. In addition, we evaluated the water resistance, hardness, and antifogging performance of the coatings. In particular, the coating produced at a 2:1 functional group ratio of POSS-C to tetraethylene glycol (OEG, n = 4) coating exhibited high surface hardness (6H), as determined using pencil scratch testing. The coating remained clear after exposure to the vapor of warm water at 40 °C at a height of 2 cm for 10 s, demonstrating its antifogging property. Furthermore, no dissolution or cracking was observed when the POSS-C/OEG coating (n = 4, COOH/OH = 2:1) was immersed in water at room temperature for 1 h, confirming its water resistance. The Fourier transform infrared/attenuated total reflectance results showed the formation of ester bonds, indicating the construction of a network structure that enhanced the water resistance and hardness of the coating.

Ionic Liquids Containing Silsesquioxane and Cyclic Siloxane Frameworks

This paper describes the author's recent work on the preparation and properties of thermally stable ionic liquids (ILs) containing siloxane frameworks. Quaternary ammonium and imidazolium salt-type ILs containing random oligosilsesquioxane frameworks were successfully prepared via the hydrolytic condensation of the corresponding organotrialkoxysilanes by using an aqueous superacid bis(trifluoromethanesulfonyl)imide (HNTf2 ) solution as a catalyst and solvent. Imidazolium salt-type ILs containing polyhedral oligomeric silsesquioxane (POSS) frameworks were also prepared through a reaction similar to that described above by using a water/methanol mixed solution of HNTf2 . In addition, amorphous POSSs with two types of ionic groups randomly distributed in the side chain were prepared. These POSSs were ILs exhibiting fluidity at relatively low temperatures. Furthermore, imidazolium and ammonium salt-type ILs containing cyclic oligosiloxane frameworks were prepared through a reaction similar to that of the corresponding organodialkoxysilanes. The thermal decomposition temperatures of the above ILs containing siloxane frameworks were higher than those of general ILs.

Design of Fluorescent Hybrid Materials Based on POSS for Sensing Applications

Polyhedral oligomeric silsesquioxane (POSS) has a nanoscale silicon core and eight organic functional groups on the surface, with sizes from 0.7 to 1.5 nm. The three-dimensional nanostructures of POSS can be used to build all types of hybrid materials with specific performance and controllable nanostructures. The applications of POSS-based fluorescent materials have spread across various fields. In particular, the employment of POSS-based fluorescent materials in sensing application can achieve high sensitivity, selectivity, and stability. As a result, POSS-based fluorescent materials are attracting increasing attention due to their fascinating vistas, including unique structural features, easy fabrication, and tunable optical properties by molecular design. Here, we summarize the current available POSS-based fluorescent materials from design to sensing applications. In the design section, we introduce synthetic strategies and structures of the functionalized POSS-based fluorescent materials, as well as photophysical properties. In the application section, the typical POSS-based fluorescent materials used for the detection of various target objects are summarized with selected examples to elaborate on their wide applications.

Preparation of Soluble POSS-Linking Polyamide and Its Application in Antifogging Films

In this study, we prepared a polyhedral oligomeric silsesquioxane (POSS)-linking polyamide (POSS polyamide) by a polycondensation of ammonium-functionalized POSS (POSS-A) and carboxyl-functionalized POSS (POSS-C) in dehydrated dimethyl sulfoxide (DMSO) using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) as condensing agents. The obtained POSS polyamide was soluble in various highly polar solvents, and it could form a self-standing film. FT-IR, ¹H NMR, and ²⁹Si NMR analyses showed that POSS polyamide is a polymer in which POSS-A and POSS-C are linked almost linearly by amide bonds. Furthermore, the cast film obtained by heat-treating the polymer at 150 °C for 30 min exhibited excellent transparency and hard-coating (pencil scratch test: 5H) and antifogging properties (evaluation by water vapor exposure).

Symmetry driven: the synthesis of co-substituent octasilsesquioxanes

Cubic octasilsesquioxanes with mixed substituents were directly synthesized through a sol–gel process using the mixture of i-butyl(triethoxysilane) and other alkoxysilanes.

First example of engineered β-cyclodextrinylated MEMS devices for volatile pheromone sensing of olive fruit pests

Olive oil is more preferred than other vegetable oils because of the increasing health concern among people throughout the world. The major hindrance in large-scale production of olive oil is olive fruit pests which cause serious economic damage to the olive orchards. This requires careful monitoring and timely application of suitable remedies before pest infestation. Herein we demonstrate efficacious utilization of covalently functionalized β-cyclodextrinylated MEMS devices for selective and sensitive detection of female sex pheromone of olive fruit pest, Bactocera oleae. Two of the MEMS devices, silicon dioxide surface-micromachined cantilever arrays and zinc oxide surface-microfabricated interdigitated circuits, have been used to selectively capture the major pheromone component, 1,7-dioxaspiro[5,5]undecane. The non-covalent capture of olive pheromones inside the β-cyclodextrin cavity leads to the reduction of resonant frequency of the cantilevers, whereas an increase in resistance has been found in case of zinc oxide derived MEMS devices. Sensitivity of the MEMS devices towards the olive pheromone was found to be directly correlated with the increasing availability of β-cyclodextrin moieties over the surface of the devices and thus the detection limit of the devices has been achieved to a value as low as 0.297 ppq of the olive pheromone when the devices were functionalized with one of the standardized protocols. Overall, the reversible usability and potential capability of the suitably functionalized MEMS devices to selectively detect the presence of female sex pheromone of olive fruit fly before the onset of pest infestation in an orchard makes the technology quite attractive for viable commercial application.

Off/On Amino-Functionalized Polyhedral Oligomeric Silsesquioxane-Perylene Diimides Based Hydrophilic Luminescent Polymer for Aqueous Fluoride Ion Detection

Fluoride ion detection in water focuses much attention due to the serious healthy impact in human pathologies. For fluoride recognition, the chemical affinity between fluoride and silicon has been developed on the basis of the degradation mechanism. However, most fluorescent probes are the "turn off" type due to the aggregation of the degradational products. Herein, we first developed an "off-on" hydrophilic luminescent polymer composed of amino-functionalized polyhedral oligomeric silsesquioxane (AE-POSS) and perylene diimides (PDIs) for fluoride ion in water. The AE-PDI polymer was "turned off" because of the photoinduced electron transfer (PET) between PDI and AE-POSS, and then after reaction with F^-, the fluorescent emission could "turn on" obviously because the PET was blocked by the degradation of the cage. The PET from amino-POSS to PDI was proved by FL spectrum and energies of HOMO and LUMO orbitals. ²⁹Si, ¹⁹F NMR, and ¹H NMR titration, XRD, FTIR, size analysis, and ion chromatography were applied to demonstrate the degradation mechanism. These results indicated that the higher quantum yield could be obtained by introducing the amide group in the PDI and the products of AE-PDI polymer might exist in the form of complex compounds with partial condensation of organosiloxane. With high selectivity and sensitivity (detection limit of 16.2 ppb), this probe was successfully applied for F^- detection in actual water samples.

Control of Crystalline-Amorphous Structures of Polyhedral Oligomeric Silsesquioxanes Containing Two Types of Ammonium Side-Chain Groups and Their Properties as Protic Ionic Liquids

Polyhedral oligomeric silsesquioxanes (POSSs), Am-POSS(x,y), prepared by hydrolytic condensation, contains two types of ammonium side-chain groups, where the numbering of x and y represents the type of ammonium ions in the POSS structure, corresponding to primary (1), secondary (2), tertiary (3), and quaternary (4) ammonium ions. Mixtures of the two starting materials selected from organotrialkoxysilanes containing primary, secondary, and tertiary amines and a quaternary ammonium salt [(RO)₃Si(CH₂)₃R′, R = CH₃ or CH₂CH₃, R′ = NH₂, NHCH₃, N(CH₃)₂, and N(CH₃)₃Cl] were dissolved in dimethyl sulfoxide (DMSO). The hydrolytic condensation was performed in the presence of bis(trifluoromethansulfonyl)imide (HNTf₂) and water. All Am-POSS(x,y) structures consisted of a cage-type octamer (T₈-POSS), as confirmed by ²⁹Si NMR spectrometry and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses indicated that Am-POSS(1,3), Am-POSS(1,4), and Am-POSS(2,4) had amorphous structures. These POSSs have two or three differences in the number of methyl groups between the two types of ammonium side-chains. Conversely, Am-POSS(1,2), Am-POSS(2,3), and Am-POSS(3,4) had crystalline structures. The difference in the number of methyl groups between the two types of ammonium side-chains in these POSSs is only one. Therefore, the crystalline-amorphous structure of Am-POSS(x,y) is controlled by the side-chain group combinations. Furthermore, Am-POSS(1,3), Am-POSS(1,4), and Am-POSS(2,4) are protic ionic liquids with relatively low flow temperatures.

Silsesquioxane cages as fluoride sensors

Pyrene functionalized silsesquioxane cages (PySQ) not only provide significant fluorescence from pyrene-pyrene excimers with a very large Stokes shift (Δλ = 143 nm, 69 930 cm^-1) in DMSO but also exhibit fluoride capture results coincidentally with a π-π* fluorescence enhancement. On the other hand, PySQ-F^- in THF significantly exhibits π-π* fluorescence quenching and a color change can be observed with the naked eye from light yellow to deep orange by forming a charge-transfer (CT) complex among the pyrenyl rings. Moreover, PySQ selectively captures F^- with a response time of <2 min and with a very low detection limit (1.61 ppb), while ¹⁹F NMR is used to confirm encapsulation of F^- with Δδ = 19 ppm.

Preparation of irrefrangible polyacrylamide hybrid hydrogels using water-dispersible cyclotetrasiloxane or polyhedral oligomeric silsesquioxane containing polymerizable groups as cross-linkers

Irrefrangible polyacrylamide hybrid hydrogels were prepared using polymerizable siloxane oligomers as cross-linkers (CyTS-MNa and POSS-MNa, respectively).

Improved epoxy thermosets by the use of poly(ethyleneimine) derivatives

Epoxy resins are commonly used as thermosetting materials due to their excellent mechanical properties, high adhesion to many substrates and good heat and chemical resistances. This type of thermosets is intensively used in a wide range of fields, where they act as fiber-reinforced materials, general-purpose adhesives, high-performance coatings and encapsulating materials. These materials are formed by the chemical reaction of multifunctional epoxy monomers forming a polymer network produced through an irreversible way. In this article the improvement of the characteristics of epoxy thermosets using different hyperbranched poly(ethyleneimine) (PEI) derivatives will be explained.

A Rapid One-Pot Synthesis of Novel High-Purity Methacrylic Phosphonic Acid (PA)-Based Polyhedral Oligomeric Silsesquioxane (POSS) Frameworks via Thiol-Ene Click Reaction

Herein, we demonstrate a facile methodology to synthesis a novel methacrylic phosphonic acid (PA)-functionalized polyhedral oligomeric silsesquioxanes (POSSs) via thiol-ene click reaction using octamercapto thiol-POSS and ethylene glycol methacrylate phosphate (EGMP) monomer. The presence of phosphonic acid moieties and POSS-cage structure in POSS-S-PA was confirmed by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (¹H, 29Si and 31P-NMR) analyses. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrum of POSS-S-PA acquired in a dithranol matrix, which has specifically designed for intractable polymeric materials. The observed characterization results signposted that novel organo-inorganic hybrid POSS-S-PA would be an efficacious material for fuel cells as a proton exchange membrane and high-temperature applications due to its thermal stability of 380 °C.

The controllable construction and properties characterization of organic–inorganic hybrid materials based on benzoxazine-bridged polysilsesquioxanes

Some controllable morphology organic–inorganic hybrid materials have been prepared via the homopolymerization of benzoxazine-bridged polysilsesquioxanes precursors with different degrees of the triethoxysilane hydrolysis condensation.

Preparation of protic ionic liquids containing cyclic oligosiloxane frameworks

Protic ionic liquids containing cyclic oligosiloxane frameworks, which were prepared by the hydrolytic condensation method, exhibited relatively high thermal stabilities.

A novel bio-engineering approach to generate an eminent surface-functionalized template for selective detection of female sex pheromone of Helicoverpa armigera

Plant pests exert serious effects on food production due to which the global crop yields are reduced by ~20–40 percent per year. Hence to meet the world’s food needs, loses of food due to crop pests must be reduced. Herein the silicon dioxide based MEMS devices are covalently functionalized for robust and efficient optical sensing of the female sex pheromones of the pests like Helicoverpa armigera for the first time in literature. The functionalized devices are also capable of selectively measuring the concentration of this pheromone at femtogram level which is much below the concentration of pheromone at the time of pest infestation in an agricultural field. Experiments are also performed in a confined region in the presence of male and female pests and tomato plants which directly mimics the real environmental conditions. Again the reversible use and absolutely trouble free transportation of these pheromone nanosensors heightens their potentials for commercial use. Overall, a novel and unique approach for the selective and reversible sensing of female sex pheromones of certain hazardous pests is reported herein which may be efficiently and economically carried forward from the research laboratory to the agricultural field.

Facile preparation of a soluble polymer containing polyhedral oligomeric silsesquioxane units in its main chain

A soluble polymer containing polyhedral oligomeric silsesquioxane (POSS) units in its main chain was successfully prepared in one-step by hydrolytic condensation of a mixture of AEAPTMS and BTMSPA using the aqueous CF₃SO₃H.

Preparation of imidazolium-type ionic liquids containing silsesquioxane frameworks and their thermal and ion-conductive properties

Imidazolium-type ionic liquids containing a random-structured (Im-Random-SQ-IL) and a cage-like (Im-Cage-SQ-IL) oligosilsesquioxanes were successfully prepared by hydrolytic condensation of MTICl in TFSI solutions in water and water/methanol solution, respectively.

Novel organic–inorganic hybrids based on T8 and T10 silsesquioxanes: synthesis, cage-rearrangement and properties

A simple approach for the synthesis of well-defined macromolecules based on isolated amino- and amido-functionalized octa T₈ and deca T₁₀ silsesquioxanes is presented. Here we show how the reorganization of the siloxane cage-like core (cage rearrangement) can be performed.

Preparation of a sulfo-group-containing rod-like polysilsesquioxane with a hexagonally stacked structure and its proton conductivity

A sulfo-group-containing rod-like polysilsesquioxane with a hexagonally stacked structure (PSQ-SO3H) was successfully prepared by oxidation and hydrolytic polycondensation of 3-mercaptopropyltrimethoxysilane (MPTMS) in a mixed aqueous solution of NaOH and H2O2. The X-ray diffraction pattern of the PSQ-SO3H film exhibited three diffraction peaks with a d-value ratio of 1:1/√3:1/2, indicating the formation of a hexagonally stacked structure. In addition, the transmission electron microscopy image of PSQ-SO3H exhibited a striped pattern, indicating that the rod-like PSQs were stacked in a parallel fashion. The presence of ionic side-chains composed of the sulfonate anions and sodium cations during the hydrolytic polycondensation of MPTMS was found to be essential for the formation of this regularly structured PSQ. Finally, the proton conductivity of the PSQ-SO3H film, determined by using complex impedance spectroscopy, was relatively high (>10(-2) S cm(-1)) at 80 °C and 30-90 % relative humidity.

Synthesis and reactivity of nitrogen nucleophiles-induced cage-rearrangement silsesquioxanes

Novel phthalimide and o-sulfobenzimide-functionalized silsesquioxanes were successfully synthesized via nucleophilic substitution reactions from octakis(3-chloropropyl)octasilsesquioxane. Surprisingly, the formation of deca- and dodecasilsesquioxanes cages was discovered during substitution with phthalimide, but only octasilsesquioxane maintained a cage in the o-sulfobenzimide substitution reaction. Moreover, we report the electronic effect of nitrogen nucleophiles to promote cage-rearrangement of inorganic silsesquioxane core for the first time. Structures of products were confirmed by (1)H, (13)C, and (29)Si NMR spectroscopy, ESI-MS analysis, and single-crystal X-ray diffraction.