Polyhedral Oligomeric Silsesquioxane Moieties Research Articles

Amphiphilic Azo-Functionalized Polyhedral Oligomeric Silsesquioxane; Synthesis and Photo-Switched Efficient Phase Transfer via Host-Guest Encapsulation.

A new amphiphilic azo-functionalized polyhedral oligomeric silsesquioxane (POSS) derivative was synthesized by functionalizing octa(3-aminopropyl)silsesquioxane (OAS-POSS) with 4-((4-(dodecyloxy)phenyl)diazenyl)benzoic acid, affording a hydrophilic amino POSS head and hydrophobic dodecyl tail with a diphenyl-azo connector. Prepared amphiphilic azo-functionalized POSS (azo-POSS) exhibited high ability for encapsulation and transferring cationic dyes into the organic phase by vigorously mixing with aqueous solutions of each dye. The photo-controlled encapsulating properties of the synthesized phase transfer reagent was studied using cationic dyes, such as methylene blue (MB), crystal violet (CV) and thymol blue in acidic conditions. Results showed more than 95 % encapsulation of MB. However, no considerable encapsulation was shown in the case of anionic dyes such as eriochrome black T (EBT) and thymol blue in alkaline solutions. By trans/cis isomerization of the azo moiety of the phase transfer reagent by UV irradiation (365 nm), the amount of dye encapsulation was decreased, which could be attributed to the formation of cis isomer that led to the folding of the dodecyl alkyl tail on the POSS moiety, and therefore prevent to lay the 3-aminopropyl moieties of POSS head to the water/DCM interface to adsorb and encapsulate MB molecules.

Photodegradable self-assembled monolayers bearing polyhedral oligosilsesquioxanes on metal oxides for the patterned deposition of silver nanoparticle ink and organic semiconductor

Three surface modifiers consisting of three parts were synthesized to fabricate photo-patternable self-assembled monolayers (SAMs) on inorganic materials for pattern-transformation; the first part is the one that binds to the surface of metal oxides (trialkoxysilane or phosphonic acid with an amino group at the end), the second is an o-nitrobenzyl (ONB) linker that protects the amino group, and the third is a hydrophobic polyhedral oligomeric silsesquioxane (POSS) that is connected to the linker. The immobilized silicon wafer with a silane coupling agent or indium tin oxide with the phosphonic acid became nearly as hydrophobic as the silicon surface-modified with perfluoroalkyl agents. After photoirradiation, the second and third parts (ONB linker with the POSS moiety) were removed and the modified surfaces became hydrophilic owing to the appearance of amino groups. This was confirmed using the contact angle of water and X-ray photoelectron spectroscopy data. Silver nano-ink or 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene was selectively deposited on the photo-irradiated region using a mask.

Toward the Highly Ordered Lamellar Hybrid Membrane for Molecular Sieving by One-Pot Self-Assembly of Hybrid Hyperbranched Polymer

Ordered lamellar hybrid membranes are of great interest, due to their application as functional materials, including molecular sieving, biosensors, optical devices, and drug, as well as gene delive...

The Synthesis and Properties of Liquid Crystalline Polyurethanes, Chemically Modified by Polyhedral Oligomericsilsesquioxanes.

In this work, we report for the first time on the influence of polyhedral oligomericsilsesquioxanes (POSS) on the structure and properties of liquid crystalline polyurethane (LCPU). LCPU/POSS hybrids were synthesized via a two-step method. In the first step, 4,4′-methylenephenyl diisocyanate (MDI) and polytetramethylene ether glycol (PTMG) reacted with functionalized trisilanolphenyl POSS (TSP-POSS) bearing three hydroxyl groups. In the second step, the growing chain was extended with 4,4′-bis(hydroxyhexoxy)biphenyl (BHHBP). FTIR measurements confirmed the chemical bonding between the POSS and LCPU matrix and showed the influence of the silsesquioxane modification on the intensity of hydrogen bonds. The DSC and POM techniques confirmed the formation of liquid crystalline phases. The incorporation of silsesquixanes into the LC matrix leads to higher melting and isotropization temperatures along with the broadening phase transition effect. Scanning electron microscopy showed a good distribution of POSS moieties, both in the bulk and on the surface of the liquid crystalline PU matrix, whereby wide-angle X-ray diffraction (WAXD) patterns revealed halos from both the liquid crystalline and unmodified polyurethane matrix. The stress at the breaking points for LCPU/POSS hybrids containing 50% and 60% of elastic segments is greater than the stress at the breaking point of the reference material (LCPU), what is due to good dispersion of POSS in less elastic matrix. Thermal properties of the LCPU/POSS materials obtained, determined by TGA, revealed that the char residue increased with the amount of POSS for 40% of elastic segments materials.

Novel Organic/Inorganic Hybrid Star Polymer Surface-Crosslinked with Polyhedral Oligomeric Silsesquioxane

Novel organic/inorganic hybrid star polymer was prepared dually crosslinked within inner-core via divinylbenzene (DVB) and outer-surface via octafunctional polyhedral oligomeric silsesquioxane (POSS). Core cross-linked star polymers bearing dialkynyl-terminated polystyrene arms, (dialkynyl-PS)n-CCL, were synthesized at first by the atom transfer radical polymerization (ATRP) of DVB using α,α-dialkynyl-terminated PS macroinitiator, followed by the subsequent fractionation. Under high dilution conditions, (dialkynyl-PS)n-CCL was subjected to surface cross-linking with octa(3-azidopropyl) polyhedral oligomeric silsesquioxane, POSS-(N3)8, via click reaction, affording POSS-functionalized hybrid polymer doubly cross-linked within core and surface regions, SCL-(PS)n-CCL. FT-IR, 1H NMR, GPC, and elemental analysis results revealed that on average, the obtained hybrid polymer possesses a cross-linked PDVB inner core, ∼14 linear PS arms (the Mw per arm of 5.1 kDa), and ∼4-5 POSS moieties at outer surface. Differential scanning calorimetry (DSC) thermograms and thermogravimetric analysis (TGA) revealed that after surface cross-linking the thermal stability of SCL-(PS)n-CCL is considerably improved. This work provides a proof-of-concept example for the preparation of dually cross-linked hybrid star polymer, which represents a novel category of organic/inorganic composite materials with unique chain architectures.

Morphology, dynamics, and order development in a thermoplastic polyurethane with melt blended POSS

ABSTRACTA top‐down approach is applied for the production of polyurethane (PU)–polyhedral oligomeric silsesquioxane (POSS) nanocomposites, namely melt blending. As opposed to the typical chemical incorporation during synthesis, a POSS moiety with two hydroxyl groups is melt blended into a commercial thermoplastic polyurethane with mass fraction up to 2 wt %. POSS disperses in the matrix in submicrometer‐sized crystals, as well as in length scale of few tens of nanometers, in the bulk. Phase separation of the produced composites was studied by both standard dynamic and isothermal annealing experiments. In an approach rare in the literature, the dynamics of phase separation is discussed based on isothermal differential scanning calorimetry curves recorded during annealing. The blended‐in nanoparticles affect the micromorphology in a complicated manner, dependent on the intrinsically complex phase separation mechanism of PU. At higher temperatures, POSS slows down the phase separation, whereas at lower ones, it enhances and accelerates it. POSS decreases the mechanical modulus of the final material, presumably as a result of changes in the microphase separation. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1133–1142

Synthesis and Near Infrared Luminescence Properties of a Series of Lanthanide Complexes with POSS Modified Ligands.

A polyhedral oligomeric silsesquioxanes (POSS) modified 8-hydroxyquinoline derivative (denoted as Q-POSS) was synthesized and used as a ligand to coordinate with lanthanide ions to obtain a series of lanthanide complexes Ln(Q-POSS)3 (Ln = Er3+, Yb3+, Nd3+). The as-prepared lanthanide complexes have been characterized by FT-IR, UV–Vis, and elemental analysis. All these complexes showed the characteristic near-infrared (NIR) luminescence originated from the corresponding lanthanide ions under excitation. Compared with the unmodified counterparts LnQ3 (HQ = 8-hydroxyquinoline), the Ln(Q-POSS)3 complexes showed obviously increased emission intensity, which was ascribed mainly to the steric-hindrance effects of the POSS moiety in the ligands. It is believed that the POSS group could suppress undesired excimer formation and intermolecular aggregation, thus decreasing the concentration quenching effect of the corresponding lanthanide complexes.

The influence of POSS nanoparticles on selected thermal properties of polyurethane-based hybrids

Organic–inorganic hybrid materials, prepared via chemical synthesis route or physical blending of functionalized nanofillers within polymer matrix, have gained an increased attention in the recent years. Polyhedral oligomeric silsesquioxane (POSS) nanoparticles, due to their nanometer size and functionalization possibilities, are applied as effective modifiers—both chemical and physical, for polymer matrices, including polyurethanes (PU). In this work, we describe the synthesis and processing of polyurethane/POSS hybrid nanocomposites and discuss the influence of POSS moieties on the thermal properties of PU matrices. Glass transition, the crystallinity of the soft phase, as well as the order–disorder transitions are affected by the incorporation of POSS in the polyurethane structure. Direct polymer-POSS interaction, or -indirect—due to the suppression or enhancement of microphase separation by the POSS moieties are discussed in terms of topology of the polymeric structure with the key role of POSS functionalization.

Dynamic Heterogeneity in Random Copolymers of Polymethacrylates Bearing Different Polyhedral Oligomeric Silsesquioxane Moieties (POSS)

Random copolymers—usually considered as dynamically homogeneous with a single glass temperature—can show dynamic heterogeneity by appropriate choice of their repeat units. Random copolymers based on polymethacrylates with polyhedral oligomeric silsesquioxane (POSS) moieties as side groups substituted with seven isobutyl ((i-Bu)7POSS-OSiMe2(CH2)3-MA) and 2,4,4-trimethylpentyl ((i-C8H17)7POSS-OSiMe2(CH2)3-MA) groups were synthesized and studied by dielectric spectroscopy, density functional theory, differential scanning calorimetry, and rheology. Two distinct relaxation processes were found by dielectric spectroscopy giving rise to two glass temperatures. In addition, rheology revealed significant broadening of the viscoelastic functions leading eventually to the failure of time–temperature superposition for all copolymer compositions. These results provide signatures of dynamic heterogeneity in a random copolymer.

Synthesis and characterization of block and random POSS/fluorinated PAES tricopolymers

Block and random polyhedral oligomeric silsesquioxane (POSS)/fluorinated poly aryl ether sulfone tricopolymers were synthesized using different synthetic strategies to investigate the effect of sequence distribution on their thermal, dielectric, and surface properties. Analyses indicated that all block and random copolymers showed similar growth tendency of water contact angles and Tg values, downward tendency of k values with increased content of POSS. The block copolymer displayed higher Tg values up to 187°C than random copolymers (173°C) under the same POSS molar percentage, which were highly related to their different sequence distribution. The dielectric constants of the tricopolymers were drastically reduced because of the presence of POSS and fluorine, and the dielectric constant could achieve as low as 2.71 (1 MHz). Besides, sequence distribution has no obvious influence on its surface properties and properties. Meanwhile, the yields of degradation residues of the tricopolymers were significantly improved by the ceramic formation from POSS moieties during thermal decomposition. Copyright © 2016 John Wiley & Sons, Ltd.

Waterborne POSS-silane-urethane hybrid polymer and the fluorinated films

Abstract A feasible co-endcapping strategy has been developed for the synthesis of monofunctional polyhedral oligomeric silsesquioxanes (POSS) modified waterborne polyurethane (WPU). The work starts from the synthesis of di-isocyanate terminated PU prepolymer from isophorone di-isocyanate (IPDI), poly (1,4-butylene adipate) end-capped diol (PBAD), and 2,2-bis(hydroxymethyl) butyric acid (DMBA). The two kinds of modifiers of monofunctional aminopropyl isobutyl POSS (AIPOSS) and with (3-aminopropyl) triethoxysilane (APTES) were used together to block the PU chains. The hybrid dispersions of curable silane-co-modified WPU with 2–8 wt% of AIRPOSS could form continuous and homogenous films under ambient conditions. The morphology and structure of the dispersed particles and the films were characterized, as well as the mechanical property and surface performance. The results indicate that the incorporation of POSS moieties into the silane-modified PU can significantly improve the mechanical property of the films and the formation of additional physical crosslinking points upon the chemical crosslinking networks. Moreover, both the surface hydrophobicity and the dielectric performance have been promoted by the incorporation of POSS. Furthermore, fluorinated groups were introduced on the films by the treatment of the fluorosilane coupling agent. The fluoro-POSS-PU hybrid films exhibit notable surface hydrophobicity as well as low dielectric constant and loss.

POSS Moieties with PEG Vertex Groups as Diluent in Polyurethane Elastomers: Morphology and Phase Separation

Polyhedral oligomeric silsesquioxane moieties with poly(ethylene glycol) groups attached on the cage (PEG–POSS) were blended with an elastomeric polyurethane matrix, in contents up to 10 wt %. Several experimental techniques in agreement with each other show that the PEG–POSS moieties disperse well on the molecular level and act as diluents plasticizing the molecular dynamics. Although the degree of microphase separation is only weakly affected in all the compositions, changes in the macromorphology related to the POSS moieties have an impact on the matrix properties, decreasing the storage modulus. The PEG–POSS themselves display segmental dynamics, glass transition, and crystallinity; however, none of these properties are observed in the blends, providing additional support for excellent miscibility with the matrix. The results are compared to those of previous works where different synthesis approaches resulting in different POSS topologies were used.

ChemInform Abstract: Cubic Polyhedral Oligomeric Silsesquioxane Based Functional Materials: Synthesis, Assembly, and Applications

AbstractReview: [61 refs.

POSS tethered hybrid “inimer” derived hyperbranched and star-shaped polymers via SCVP-RAFT technique

Design and synthesis of highly efficient branching agent (“inimer”) to prepare hyperbranched architectures with tunable physical and chemical properties is one of the most challenging and interesting topic to the polymer community. Here, we report the rational design of a new polyhedral oligomeric silsesquioxane (POSS) containing “inimer” and employed in reversible addition-fragmentation chain transfer (RAFT) copolymerization with various vinyl monomers such as styrene (St), polyethylene glycol methyl ether methacrylate (PEGMA) and N,N-dimethyl acrylamide (DMA) to develop novel hybrid hyperbranched copolymers. Degree of branching (DB) and average repeat unit per branch (RB) of the resulting hyperbranched copolymers have been fine-tuned by altering the [monomer]/[inimer] ratios. Hyperbranched copolymers such as poly(St) and poly(PEGMA) were successively employed to prepare star-shaped polymers with controllable arm length. Self-assembly behavior of star-shaped polymers was investigated in methanol, where a wide spectrum of morphologies including sphere, ellipsoid and vesicle could be achieved simply via tuning the availability of POSS moiety, DB of the methanophobic hyperbranched core and/or the length of methanophilic arms.

Cubic Polyhedral Oligomeric Silsesquioxane Based Functional Materials: Synthesis, Assembly, and Applications.

Organically modified cubic polyhedral oligomeric silsesquioxanes (POSS) have attracted increasing attention in the design of novel functional hybrid materials for applications such as porous materials, liquid crystals, semiconductors, high-temperature lubricants, fuel cells, and lithium batteries. The nanosized POSS moiety can be conveniently modified on the periphery with a variety of functional groups to lead to hybrid materials with desired functions. In addition, suitable mono-functionalized POSS derivatives can be incorporated into polymers as side chains via various synthetic strategies to offer a wide class of functional polymeric materials with tunable physical properties for targeted applications. In this Focus Review, we aim to summarize the recent developments on the chemistry and applications of POSS-based molecules and polymers. Moreover, the properties as well as assembly behavior of the POSS-based functional hybrid materials will be reviewed, and the relationship of the performance of the hybrid materials with the intrinsic nature of the POSS unit will be addressed.

Controlled synthesis of amino-acid based tadpole-shaped organic/inorganic hybrid polymers and their self-assembly in aqueous media

Synthesis, characterization and solution behavior of tadpole-shaped amphiphilic polymers with hydrophobic polyhedral oligomeric silsesquioxane (POSS) chain-end and hydrophilic main-chain having leucine pendants were investigated. Reversible addition-fragmentation chain transfer (RAFT) polymerization technique was employed to polymerize tert-butyloxycarbonyl-l-leucine methacryloyloxyethyl ester (Boc-Leu-HEMA) in the presence of POSS based RAFT agent. The POSS content and molecular weight of polymers could be controlled while maintaining a narrow molecular weight distribution (<1.3). Glass transition temperature (Tg) of tadpole shaped polymers (TSP) increased with increasing content of POSS moiety in the polymer matrix. Circular dichroism (CD) spectroscopy confirmed that the POSS moiety did not perturb the higher ordered secondary conformation of TSP, attained due to the presence of pendent chiral leucine moiety. Expulsion of side chain Boc groups produced pH responsive amphiphilic cationic polymers, which exhibited self-assembly in aqueous medium, confirmed by dynamic light scattering (DLS) and field-emission scanning electron microscopy (FE-SEM). The aggregation behavior of POSS end-capped polymeric nanoparticles was further investigated through nile red encapsulation as a hydrophobic probe in aqueous medium.

POSS-Containing Jacketed Polymer: Hybrid Inclusion Complex with Hierarchically Ordered Structures at Sub-10 nm and Angstrom Length Scales

A series of organic–inorganic hybrid polymers, PnPOSS (n = 6, 10, which is the number of carbon atoms in the flexible alkyl spacers), containing a mesogen-jacketed liquid crystalline polymer (MJLCP) as the main chain and a crystalline nanobuilding block, polyhedral oligomeric silsesquioxane (POSS), in the side chains were designed and synthesized for constructing a hybrid inclusion complex. The phase structures and phase transitions of PnPOSS were investigated by differential scanning calorimetry, polarized light microscopy, wide-angle X-ray diffraction, small-angle X-ray scattering, and high-resolution transmission electron microscopy. With the competitive self-assemblies of the two covalently connected building blocks, namely MJLCP and POSS moieties, PnPOSS shows various phase structures including a sub-10 nm hexagonal columnar (Colh) or columnar nematic liquid crystalline phase, an angstrom rhombohedral crystalline (KR) phase, and a hierarchically ordered phase with Colh and KR coexisting. This work provides a new approach for the design and synthesis of hybrid inclusion materials.

Synthesis of High Molecular Weight Polymethacrylates with Polyhedral Oligomeric Silsesquioxane Moieties by Atom Transfer Radical Polymerization.

A new polyhedral oligomeric silsesquioxane (POSS) methacrylate monomer, 1-(3-(methacryloyloxy)propyl)dimethylsiloxy-3,5,7,9,11,13,15-hepta(isobutyl)pentacyclo-[9.5.1.13,9.15,15.17,13]octasiloxane ((i-Bu)7POSS-OSiMe2-MA, 1), with a flexible spacer between the cubic POSS cage and methacrylate group was synthesized to reduce steric strain and thus achieve polymethacrylates (poly(POSS-MA)s) with high molecular weight (MW). Atom transfer radical polymerization (ATRP) of 1 at high monomer concentration (1 M, corresponding to ca. 85 wt % of 1) led to polymers with the absolute number-average MW, determined by multiangle laser light scattering, Mn,MALLS = 2 350 000 (and apparent MW, measured by gel permeation chromatography with linear poly(methyl methacrylate) (PMMA) standards, Mn,GPC = 550 000). Optimization of the reaction conditions, including the ATRP catalyst, targeted degrees of polymerization, monomer concentrations, as well as a monomer feeding, resulting in the first well-defined high MW polymers with POSS moieties.

Size-Tunable Nanosheets by the Crystallization-Driven 2D Self-Assembly of Hyperbranched Poly(ether amine) (hPEA)

We reported the preparation of uniform square nanosheets with tunable size by the living crystallization-driven 2D self-assembly of hyperbranched poly(ether amine) capped with heptaisobutyl polyhedral oligomeric silsesquioxane (POSS). The nanosheets of HP1 containing both anthracene (AN) and POSS moieties in a solution of 1,4-dioxane and water can be fragmented after the melting of the POSS moieties upon heating and can be regenerated after the recrystallization of POSS moieties, which was confirmed by microdifferential scanning calorimetry (μDSC) and dynamic light scattering (DLS) studies and transmission electron microscopy (TEM) images. The obtained fragmented nanosheets (HP1-NSs) with a relatively small size were used as seeds for the 2D epitaxial living growth of HP1 unimers to fabricate uniform square nanosheets with tunable edge lengths from ∼0.5 to ∼4.5 μm, which is dependent on the unimer-to-seed ratio. Furthermore, dual-component nanosheets can also be obtained by random cocrystallization of HP1...

Synthesis of Organic/Inorganic Polyhedral Oligomeric Silsesquioxane-Containing Block Copolymers via Reversible Addition–Fragmentation Chain Transfer Polymerization and Their Self-Assembly in Aqueous Solution

Polyhedral oligomeric silsesquioxane (POSS)-containing homopolymers (PHEMAPOSS) with a high degree of polymerization (DP) were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. PHEMAPOSS was used as a macro-RAFT agent to construct a series of amphiphilic diblock copolymers, PHEMPOSS-b-PMAA (poly (methyl methacrylate)), which possessed a different length of hydrophilic chains. The self-assembly behavior of PHEMPOSS-b-PMAA in aqueous solution was studied by transmission electron microscopy (TEM), atomic force microscopy (AFM), and dynamic light scattering (DLS), respectively. The results showed that PHEMAPOSS45-b-PMAA523 forms typical core–shell spherical micelles where the hydrophobic PHEMAPOSS blocks as the core and hydrophilic PMAA blocks as the shell. With increasing PMAA chain length, PHEMAPOSS45-b-PMAA1173 with a longer PMAA chain self-assembled into irregular aggregates with POSS moieties dispersed in the aggregates. On the other hand, PHEMAPOSS45-b-PMAA308 with ...