Poly(ethylene imine) hybrids containing polyhedral oligomeric silsesquioxanes: Preparation, structure and properties

Both octaglycidyletherpropyl polyhedral oligomeric silsesquioxane and hepta(3,3,3-trifluoropropyl)glycidyletherpropyl polyhedral oligomeric silsesquioxane were synthesized via the hydrosilylation reactions between octahydrosilsesquioxane [and/or hepta(3,3,3-trifluoropropyl)hydrosilsesquioxane] and allyl glycidyl ether. The polyhedral oligomeric silsesquioxane (POSS) macromers were characterized by means of Fourier transform infrared and nuclear magnetic resonance spectroscopy. The inter-component macromolecular reactions between the POSS macromers and poly(ethylene imine) (PEI) were employed to prepare the POSS-containing organic-inorganic PEI hybrids. The inclusion of octaglycidyletherpropyl POSS into PEI results in the formation of the organic-inorganic hybrid networks whereas the introducing hepta(3,3,3-trifluoropropyl)glycidyletherpropyl POSS to PEI affords the linear POSS-grafted PEI copolymers. Differential scanning calorimetry and thermogravimetric analysis show that the POSS-containing PEI hybrids displayed increased glass transition temperatures (T_g’s) and enhanced thermal stability compared to the plain PEI. These PEI hybrid composites can be significantly swollen with water without dissolving, suggesting the formation of hydrogels. The PEI hydrogels containing octaglycidyletherpropyl POSS is in reality the chemically-crosslinked hydrogels whereas the those containing hepta(3,3,3-trifluoropropyl)glycidyletherpropyl POSS displayed the behavior of physical hydrogels. The formation of physical hydrogels is ascribed to the microphase-separated morphology in the hybrids. In addition, the hybrids containing hepta(3,3,3-trifluoropropyl)glycidyletherpropyl POSS exhibited the typical amphiphilicity as evidenced by the increase in surface hydrophobilicity.     

Pd on magnetic hybrid of halloysite and POSS-containing copolymer: An efficient catalyst for dye reduction

A novel catalytic nanocomposite, MNPs/Hal-POSS-HEMA-Pd, composed of halloysite nanoclay and polyhedral oligomeric silsesquioxane is reported. To synthesize the catalyst, magnetic halloysite was vinyl functionalized and then polymerized with 2-hydroxyethyl methacrylate and methacrylate polyhedral oligomeric silsesquioxane. Afterwards, the latter was palladated to furnish a heterogeneous catalyst with use for catalyzing the reductive degradation of organic dyes, Rhodamine B, and methyl orange with NaBH₄. The kinetic and thermodynamic parameters of both reactions were estimated. The results asserted that low content of the catalyst could catalyze the dye reduction reactions to furnish hydrogenated product in quantitative conversion in a very short reaction times (1 min). It is assumed that both halloysite and polyhedral oligomeric silsesquioxane can contribute to the anchoring of Pd nanoparticles. On the other hand, the polymeric network around halloysite can furnish a microenvironment for bringing dyes in the vicinity of active sites. Moreover, unique tubular morphology of halloysite can effectively improve dye adsorption and consequently enhance dye reduction. Additionally, the study of the recyclability of the catalyst approved that it could be magnetically recovered and reused for ten successive reaction runs with trivial leach of Pd (2 wt.%) and decrement of the catalytic activity.     

Peptide dendrimer-crosslinked inorganic-organic hybrid supramolecular hydrogel for efficient anti-biofouling

A novel kind of inorganic-organic hybrid supramolecular hydrogel with excellent anti-biofouling capability was developed. The hydrogel was formed via ionic interaction between the negative-charged sodium polyacrylate (SPA) entwined clay nanosheets (CNS) and positive-charged polyhedral oligomeric silsesquioxane (POSS) core-based generation one (L-Arginine) dendrimer (POSS-R).     

Synthesis and characterization of polyhedral oligomeric silsesquioxane hybrid co‐crosslinked poly(N‐isopropylacrylamide‐co‐dimethylaminoethyl methacrylate) hydrogels

Polyhedral oligomeric silsesquioxane hybrid temperature and pH double‐responsive hydrogels with organic–inorganic co‐crosslinked networks are synthesized by in situ, free‐radical polymerization of N‐isopropylacrylamide and dimethylaminoethyl methacrylate in the presence of both organic crosslinker N,N′‐methylenebis(acrylamide) (BIS) and inorganic crosslinker octavinyl polyhedral oligomeric silsesquioxane (OvPOSS) in tetrahydrofuran media. The resulting hydrogels (OR‐OvP gels) display obvious temperature and pH double responsiveness, OvPOSS particles dispersed in polymer make a dominant effect on the properties of gels. With the increase of OvPOSS, the aggregation of particles on nano‐ or microscale happens and causes a considerable change on the properties of gels, such as the lower critical solution temperature and better compression strength. Specially, the interconnected microporous structure of gels ascribed to the microphase separation results in faster deswelling rate, which makes the gel become attractive. Besides, the crosslink by BIS intensifies the heterogeneity of gels significantly, which could also be used to adjust the properties of gels. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1494–1504     

倍半硅氧烷改性环氧树脂的研究进展

倍半硅氧烷是近年发展起来的一种分子水平的有机无机杂化材料。文章介绍了倍半硅氧烷的结构、合成以及笼型倍半硅氧烷（POSS）基高分子复合材料的结构及合成方法。倍半硅氧烷改性聚合物可以提高聚合物的热性能、阻燃性能和物理机械性能等。文章综述了倍半硅氧烷改性环氧树脂的研究进展。     

Poly(N-isopropylacrylamide) nanocrosslinked by polyhedral oligomeric silsesquioxane: temperature-responsive behavior of hydrogels

Octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OpePOSS) was used as a nanocrosslinking agent to prepare the crosslinked poly(N-isopropylacrylamide) (PNIPAM) networks with POSS content up to 50 wt%. The inter-component crosslinking was achieved via the reaction between NH moieties in amide group of PNIPAM and epoxide groups of OpePOSS. When the organic-inorganic nanocomposites were swollen in water the POSS-crosslinked PNIPAM exhibited the characteristics of hydrogels. With the moderate contents of POSS, the POSS-containing hybrid hydrogels displayed much faster response rates in swelling, deswelling and reswelling experiments than the PNIPAM hydrogels prepared via the free radical copolymerization of N-isopropylacrylamide (NIPAM) and N,N(')-methylenebisacrylamide (viz. the conventional crosslinker). The improved hydrogel properties have been interpreted on the basis of the formation of the nanosized hydrophobic microdomains around the POSS moieties (i.e., the nanocrosslinking sites).     

Interfacial Activity of Amine‐Functionalized Polyhedral Oligomeric Silsesquioxanes (POSS): A Simple Strategy To Structure Liquids

Amine‐functionalized polyhedral oligomeric silsesquioxane (POSS), the smallest, monodisperse cage‐shaped silica cubic nanoparticle, is exceptionally interfacially active and can form assemblies that jam the toluene/water interface, locking in non‐equilibrium shapes of one liquid phase in another. The packing density of the amine‐functionalized POSS assembly at the water/toluene interface can be tuned by varying the concentration, the pH value, and the degree of POSS functionalization. Functionalized POSS gives a higher interface coverage, and hence a lower interfacial tension, than nanoparticle surfactants formed by interactions between functionalized nanoparticles and polymeric ligands. Hydrogen‐bonded POSS surfactants are more stable at the interface, offering some unique advantages for generating Pickering emulsions over typical micron‐sized colloidal particles and ligand‐stabilized nanoparticle surfactants.     

The preparation and properties of hybridized hydrogels based on cubic thiol-functionalized silsesquioxane covalently linked with poly(N-isopropylacrylamide)

Firstly, nano-sized polyhedral oligomeric silsesquioxane with functional mercapto groups (POSS-SH) was prepared through hydrolytic condensation of 3-mercaptopropyl trimethoxysilane. Then N-isopropylacrylamide (NIPAm) was allowed to polymerize at the presence of POSS-SH and N,N-methylene-bisacrylamide to yield hybridized hydrogels. The hybridized hydrogels demonstrated thermosensitive behavior across the volume phase transition temperatures. The swelling and deswelling rates were greatly accelerated through the incorporating of POSS-SH into the gels, and the thermal properties of the hybridized hydrogels were reinforced compared with the neat PNIPAm hydrogel. These results were ascribed to nano-effect created by the hydrophobic POSS-SH nanoparticles. The hybridized hydrogels have potential applications in drug controlled release.     

Cationic polyhedral oligomeric silsesquioxane (POSS) units as carriers for drug delivery processes

Quaternary ammonium functionalized polyhedral oligomeric silsesquioxane (OctaAmmonium-POSS) units, widely employed as additives in ceramic and polymeric systems, possess many attributes which make them attractive as biocompatible drug carriers: nanoscale size, three-dimensional functionality, efficient cellular uptake, low toxicity, and high solubility.     

Efficient Photocatalytic Cleavage of Lignin Models by a Soluble Perylene Diimide/Carbon Nitride S-Scheme Heterojunction

3,4,9,10-Perylenetetracarboxylic dianhydride (PDI) is one of the best n-type organic semiconductors and an ideal light-driven catalyst for lignin depolymerization. However, the charge localization effect and the excessively strong intermolecular aggregation trend in PDI result in rapid electron-hole (e⁻−h⁺) recombination, which limits photocatalytic performance. Herein, polymeric carbon nitride/polyhedral oligomeric silsesquioxane PDI (p-CN/P-PDI) S-scheme heterojunction photocatalyst was prepared by the solvent evaporation-deposition method for C−C bond selective cleavage of lignin β-O-4 model. Based on the material characterization results, the synergic role of polyhedral oligomeric silsesquioxane (POSS) and S-scheme heterojunction maintains appropriate aggregation domains, achieves better solar light utilization, faster charge-transfer efficiency, and greater redox capacity. Notably, the 3 % p-CN/P-PDI heterostructure exhibits a remarkable enhancement in cleavage conversion efficiency, achieving approximately 16.42 and 2.57 times higher conversion rates compared to polyhedral oligomeric silsesquioxane modified PDI (POSS-PDI) and polymeric carbon nitride (p-CN), respectively.     

Soluble and film-formable homopolymer tethering side-opened cage silsesquioxane pendants

Cage silsesquioxane, denoted as polyhedral oligomeric silsesquioxane (POSS) has high crystallinity to readily cause aggregation when it is induced into polymer side chain. In this work, side-opened POSS was employed to construct a bifunctional monomer for cyclopolymerization. The collapsed symmetry of the POSS core effectively reduced the crystallinity to realize homogeneous films, while a traditional POSS homopolymer formed turbid and brittle films. The obtained film showed high transparency and thermal stability.     

POSS nanocrosslinked poly (ethylene glycol) hydrogel as hybrid material support for silver nanocatalyst

Silver nanoparticles supported on polyhedral oligomeric silsesquioxane (OA‐POSS) nanocrosslinked poly (ethylene glycol)‐based hydrogels (PEG₆₀₀‐POSS/Ag NPs) as novel nanohybrid catalysts were synthesized for the first time. The as‐prepared nanohybrid hydrogels were fully characterized by FT‐IR, SEM, EDX, XRD, TEM and TGA. PEG₆₀₀‐POSS/Ag NPs exhibited excellent catalytic performance for the reduction of 4‐nitrophenol (4‐NP) to 4‐aminophenol (4‐AP) in water at room temperature in the presence of borohydride.     

Synthesis and Viscoelastic Properties of Hydrophobically Modified Hydrogels

Summary: We report the synthesis and characterization of a family of hydrophobically modified hydrogels designed to have an improved fracture resistance. A backbone of poly(acrylic acid) (PAA) was functionalized with double bonds and hydrophobic groups. The functionalized PAA was then crosslinked with a dithiol. The chemical structure of the gels was characterized with a combination of NMR, titration methods and rheological techniques. The crosslinked structure of the hydrogel was found to be dependent on the polymer concentration only, while the dissipative properties of the gel increased strongly at all frequencies, with the introduction of hydrophobic groups which formed reversible associations. We expect these viscoelastic hydrogels to display dramatically different properties from the unmodified hydrogels when stretched and fractured.     

Epoxy networks modified by multifunctional polyhedral oligomeric silsesquioxanes (POSS) containing amine groups

The hydrolytic condensation of a precursor synthesized by the reaction of equimolar amounts of (3-aminopropyl)triethoxysilane and phenylglycidylether led to a distribution of polyhedral oligomeric silsesquioxanes (POSS) containing 8–11 Si atoms, functionalized with amine groups. About 57% of the NH functionalities were active for reaction with epoxy groups. The multifunctional amine-POSS was used to modify an epoxy network obtained by the homopolymerization of diglycidylether of bisphenol A initiated by benzyldimethylamine. The main effect of POSS modification was an increase in both the glassy and rubbery modulus explained, respectively, by the increase in cohesive energy and crosslink densities.     

Inorganic–organic nanocomposites of polybenzoxazine with octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane

Octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OpePOSS) was used to prepare the polybenzoxazine (PBA‐a) nanocomposites containing polyhedral oligomeric silsesquioxane (POSS). The crosslinking reactions involved with the formation of the organic–inorganic networks can be divided into the two types: (1) the ring‐opening polymerization of benzoxazine and (2) the subsequent reaction between the in situ formed phenolic hydroxyls of PBA‐a and the epoxide groups of OpePOSS. The morphology of the nanocomposites was investigated by means of scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Differential scanning calorimetry and dynamic mechanical analysis showed that the nanocomposites displayed higher glass‐transition temperatures than the control PBA‐a. In the glassy state, the nanocomposites containing less than 30 wt % POSS displayed an enhanced storage modulus, whereas the storage moduli of the nanocomposites containing more than 30 wt % POSS were lower than that of the control PBA‐a. The dynamic mechanical analysis results showed that all the nanocomposites exhibited enhanced storage moduli in the rubbery states, which was ascribed to the two major factors, that is, the nanoreinforcement effect of POSS cages and the additional crosslinking degree resulting from the intercomponent reactions between PBA‐a and OpePOSS. Thermogravimetric analysis indicated that the nanocomposites displayed improved thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1168–1181, 2006     

Hydrolytic degradation of POSS-PEG-lactide hybrid hydrogels

A polyhedral oligomeric silsesquioxane (POSS), functionalized with eight arms of poly(ethylene glycol) (PEG; MW 400) and then acrylated, was incorporated into a hydrogel network based on triblock copolymers of poly(lactide-b-ethylene glycol-b-lactide) diacrylates using a redox-initiated polymerization. The organic-inorganic hybrid hydrogels so prepared contained the inorganic crosslinker POSS from 1 to 28 wt.%. The degradation properties of the hydrogels in a pH 7.4 phosphate-buffered saline solution at 37 °C were studied using measurements of mass loss, cryogenic SEM, and ATR-FTIR spectroscopy. It was found that copolymerization of acrylated 1kPEG-lactide with increasing amounts of POSS created a more porous network which was more resistant to hydrolysis. The ATR-FTIR technique was used to monitor the progress of degradation with exposure time through the changes in the carbonyl and C-H deformation bands of the lactide and the Si-C stretching band of the POSS. Increasing POSS incorporation resulted in decreased rate of degradation due to its hydrophobic nature and inertness to hydrolysis. Conversely, an increase in lactide content increased the degradation rate due to the increased number of hydrolytically-sensitive ester groups in the network.     

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.     

POSS‐based poly(aryl ether sulfone)s random terpolymer linked POSS to the main chain: effect of chemical structure and POSS content on properties

In order to investigate the effect of polyhedral oligomeric silsesquioxane content and the structure‐function related on the dielectric property and hydrophobicity, three kinds of poly(aryl ether sulfone)s (PAESs) random terpolymer with different chemistry structure at variable polyhedral oligomeric silsesquioxane content in the main chain are prepared. The structures of PAESs are characterized by infrared (IR), nuclear magnetic resonance (NMR), and wide‐angle X‐ray diffraction (WXRD) spectra. The results show that the dielectric constant initially increases then decrease to 2.68 at 100%‐double‐decker silsesquioxane (DDSQ)‐PAES(molar content of DDSQ = 100%) at 1 MHz. The contact angle increased to 97.5° at 100%‐DDSQ‐PAES. While the chemical structure of organic chains also plays an important role on thermostability, dielectric, and hydrophobic properties. The results are discussed and interpreted in detail. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation and characterization of Fe3O4@SiO2/APTPOSS core–shell composite nanomagnetics as a novel family of reusable catalysts and their application in the one‐pot synthesis of 1,3‐thiazolidin‐4‐one derivatives

Octakis[3‐(3‐aminopropyltriethoxysilane)propyl]octasilsesquioxane (APTPOSS) as a polyhedral oligomeric silsesquioxane derivative was prepared and used as a pioneer reagent to obtain a novel core–shell composite using magnetic iron oxide nanoparticles as the core and the inorganic–organic hybrid polyhedral oligomeric silsesquioxane as the shell. Fe₃O₄@SiO₂/APTPOSS were confirmed using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, dynamic light scattering, thermogravimetric analysis, X‐ray diffraction and vibrating sample magnetometry. The inorganic–organic hybrid polyhedral oligomeric silsesquioxane magnetic nanoparticles were used as an efficient new heterogeneous catalyst for the one‐pot three‐component synthesis of 1,3‐thiazolidin‐4‐ones under solvent‐free conditions. Moreover, these nanoparticles could be easily separated using an external magnet and then reused several times without significant loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and properties of low‐dielectric‐constant polyimides with introduced reactive fluorine polyhedral oligomeric silsesquioxanes

A high‐performance, low‐dielectric‐constant polyimide (PI) nanocomposite from poly(amic acid) (PAA) cured with a reactive fluorine polyhedral oligomeric silsesquioxane (POSS) isomer was successfully synthesized. The features of this reactive fluorine POSS isomer [octakis(dimethylsiloxyhexafluoropropylglycidyl ether)silsesquioxane (OFG)] provided two important approaches (containing fluorine or being porous in the polymer matrix) of reducing the dielectric constant of PI. This reactive POSS isomer had an average of four epoxy groups and four fluorine groups on the POSS cage, and the epoxy groups could be cured with PAA to form a network framework of a PI/POSS nanocomposite. The PI/OFG nanocomposite had a high crosslinking density, high porosity (24.3%), high hydrophobicity, and low polarizability. These properties enhanced the thermal (glass‐transition temperature ～ 362 °C) and dielectric (dielectric constant ～2.30) properties of PI more than other POSS derivatives introduced into the PI backbone. A large number of small POSS particles (<10 nm) were embedded inside the PI matrix when the OFG content was low, whereas interconnected POSS aggregation domains were observed when the OFG content was high. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5391–5402, 2006