POSS Contents Research Articles

Engineering the Surface Pattern of Microparticles: From Raspberry-like to Golf Ball-like.

Control of the shape and uniformity of colloid particles is essential for realizing their functionality in various applications. Herein, we report a facile approach for the synthesis of narrowly dispersed anisotropic microparticles with well-defined raspberry-like and golf ball-like surface patterns. First, we demonstrate that hybrid raspberry-like particles can be achieved through a one-pot polymerization method using glycidyl polyhedral oligomeric silsesquioxane (GPOSS) and pentaerythritol tetra(3-mercaptopropionate) (PETMP) as monomers. Varying the polymerization parameters such as catalyst loading, monomer concentration, and the molar ratio of monomers, we are able to regulate the sizes and surface protrusion numbers of these raspberry-like microparticles. The formation mechanism is attributed to a competition balance between thiol-epoxy reaction and thiol-thiol coupling reaction. The former promotes rapid formation of large core particles between PETMP and GPOSS droplets (which can serve as core particles), while the latter allows for generation of surface protrusions by PETMP self-polymerization, leading to the formation of raspberry-like surface patterns. Based on the different POSS contents in the surface protrusions and cores of the raspberry-like microparticles, we demonstrate that they can be used as precursors to produce microporous silica (sub)microparticles with golf ball-like morphology via pyrolysis subsequently. Overall, this work provides a facile yet controllable approach to synthesize narrowly dispersed anisotropic microparticles with diverse surface patterns.

Silicone-enriched surface of immersed polyurethane-POSS antifouling coating

A series of waterborne polyurethane-polyhedral oligomeric silsesquioxane (WBPU-POSS) dispersions were synthesized. Different POSS contents were used to evaluate the effect of POSS content on silicone enrichment under both nonimmersed and immersed conditions. The impact of silicone enrichment under immersed conditions on antifouling properties was also evaluated. The structure of the WBPU-POSS coating was identified by FT-IR and 29Si-NMR. X-ray photoelectron spectroscopy (XPS) analysis confirmed a silicone-enriched surface with a certain composition of the WBPU-POSS coating under both nonimmersed and immersed conditions. The mechanical properties, hydrophilicity and hydrolytic degradation of the coating all varied with POSS content. The long-term antifouling performance of immersed coatings depends on surface silicone enrichment, which was found to be above 0.0021 mole POSS content in WBPU-POSS coatings.

The synergistic effect of graphene oxide and POSS in mixed matrix membranes for desalination

The effect of Graphene Oxide (GO) and POSS nanoparticles on the Reverse Osmosis (RO) desalination performance of Mixed Matrix Membranes (MMMs) was investigated experimentally. Cellulose Acetate (CA) nanocomposite membranes with different GO and POSS contents were prepared by the phase inversion method. The Response Surface Method (RSM) was used to evaluate interactions between the main parameters and to optimize the performance of the membrane. A Box-Behnken Design (BBD) analysis was carried out for the simultaneous increase of salt rejection and permeation flux, and optimal GO and POSS concentrations and operating pressure were obtained at 0.005 wt% and 0.75 wt%, and 19.2 atm. The membrane was prepared and tested under optimal conditions, and a permeation flux of 13.65 l/m2.h and salt rejection of 77.83% was achieved which were in good agreement with the estimated results (12.95 l/m2.h and 79.94%). Consequently, BBD optimization within the range of experimental parameters can be employed as a reliable method for predicting the desalination performance of CA/GO/POSS membrane.

Improving the Damping Properties of Nanocomposites by Monodispersed Hybrid POSS Nanoparticles: Preparation and Mechanisms.

In this work, a series of heptaphenyl siloxane trisilanol/polyhedral oligomeric silsesquioxane (T7-POSS) modified by polyols with different molecular weights were synthesized into liquid-like nanoparticle–organic hybrid materials using the grafted-from method. All grafted POSS nanoparticles changed from solid powders to liquid at room temperature. Polyurethane (PU) nanocomposites with POSS contents ranging from 1.75 to 9.72 wt % were prepared from these liquefied polyols-terminated POSS with polyepichlorohydrin (POSS–PECH). Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the morphology of the POSS–PECH/PU nanocomposites. The results showed that the polyol-terminated POSS particles overcame the nanoagglomeration effect and evenly disperse in the polymeric matrix. The damping factor (tan δ) of resultant nanocomposites increased from 0.90 to 1.16, while the glass transition temperature decreased from 15.8 to 9.4 °C when POSS contents increased from 0 to 9.75 wt %. The gel content, tensile strength and Fourier transform infrared (FTIR) analyses demonstrated that the molecular thermal movement ability of the polyurethane (PU) matrix increased with increasing POSS hybrid content. Therefore, the improvement of the damping properties of the composites was mainly due to the friction-related losses occurring in the interface region between the nanoparticles and the matrix.

Improving Damping Properties and Thermal Stability of Epoxy/Polyurethane Grafted Copolymer by Adding Glycidyl POSS

Modified castor oil-based epoxy resin (EP)/polyurethane (PU) grafted copolymer by glycidyl polyhedral oligomeric silsesquioxane (glycidyl POSS) was synthesized. The damping properties, thermal stability, mechanical properties and morphology of the grafted copolymer modified by glycidyl POSS were studied systematically. The results revealed that the incorporation of glycidyl POSS improved the damping performance evidently and broadened damping temperature range, especially when the glycidyl POSS content was 0.2%–1%. At the same time, there was a slight increase in thermal stability with the increase of POSS content. The tensile properties changed with the change of the copolymer’s Tg, decreased at low POSS contents and increased at high POSS contents. This modified copolymer has the potential to be used as film damping material or constrained damping layer.

Enhanced electrical and thermal performances of nanostructured epoxy/POSS composites

Epoxy resins modified with Glycidyl-POSS (Polyhedral Oligomeric Silsesquioxanes) in contents of up to 20 wt% were fabricated and studied in terms of dielectric spectroscopy, differential scanning calorimetry, AC breakdown tests, thermal conductivity measurements and corona resistance. Microstructure analysis have revealed a molecular dispersion of Glycidyl-POSS up to contents of 10 wt%, whereas in the 20 wt% POSS composites crystalline zones due to POSS could be observed by both scanning electron microscopy and transmission electron microscopy. All POSS composites have seen a significant improvement in AC breakdown strength, as well as an enhanced resistance to corona discharges, which in the latter case was getting more pronounced with higher POSS loadings. On the contrary, low POSS contents proofed most effective in improving the thermal conductivity, which should be attributed to the effect of POSS on the nanostructure of the polymeric network.

The impact of ultra-low amounts of introduced reactive POSS nanoparticles on structure, dynamics and properties of densely cross-linked cyanate ester resins

Thermostable nanocomposites based on densely cross-linked Cyanate Ester Resins (CER), derived from bisphenol E and doped by 0.01–10wt.% epoxycyclohexyl-functionalized polyhedral oligomeric silsesquioxane (ECH-POSS), were synthesized and characterized in detail by means of TEM, SAXS, EDXS, FTIR, DSC, DMA, TGA, far-IR and creep rate spectroscopy techniques. It was revealed that ultra-low POSS contents (≪1wt.%), covalently embedded into CER network, substantially changed its nanostructure and properties. This resulted in changing network dynamics; increasing glass transition temperatures by 20–50°C; enhancing high temperature elastic and creep resistance properties, and increasing thermal stability under inert atmosphere at T<400°C. The effects being observed decreased, or even became zero or negative, while increasing POSS content, especially from 2 to 10wt.%, due to arising the structural nanorod- or platelet-like formations and POSS-enriched nanodomains. At ultra-low POSS contents, the data obtained suggest basically molecular POSS dispersion, their quasi-periodic spatial distribution in the matrix, and not only chemical modifying CER network but also the possible manifestation of the enhanced long-range action of the “constrained dynamics” effect.

Synthesis of MA POSS–PMMA as an intraocular lens material with high light transmittance and good cytocompatibility

Poly(methyl methacrylate) (PMMA) has been widely used for intraocular lenses (IOL) but may lead to posterior capsule opacification (PCO) after implantation due to its undesirable hydrophilicity and surface morphology. A novel methacrylisobutyl polyhedral oligomeric silsesquioxane-co-poly methyl methacrylate copolymer (MA POSS–PMMA) was synthesized by a free radical polymerization method to improve its material properties and cytocompatibility. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and proton nuclear magnetic resonance spectroscopy (1H NMR) measurements demonstrated the successful synthesis of MA POSS–PMMA copolymer. The incorporation of MA POSS greatly changed the crystal structure, surface wettability, optical transmission and cytocompatibility of PMMA. XRD peaks at 2θ ∼ 38.5, 44.7 and 66.1° indicated that a portion of the MA POSS molecules had aggregated and crystallized. Furthermore, larger aggregates are formed at higher MA POSS contents. The optical transmission of the copolymers was up to 99%, which was better than pure PMMA. The hydrophilicity and morphology of the IOL surface were characterized by static water contact angle and atomic force microscopy. Results revealed that MA POSS rendered the surface more hydrophobic and with higher roughness than the pure PMMA. Biocompatibility of copolymers with human lens epithelial cells (HLECs) was further evaluated by morphology and activity measurements in vitro. More HLECs adhesion and better spreading morphology on the surfaces of MA POSS–PMMA copolymers than that on PMMA was shown.

Morphology and properties of UV-curing epoxy acrylate coatings modified with methacryl-POSS

Abstract In this work, the morphology and properties of UV-curing epoxy acrylate (EA) coatings modified with methacryl polyhedral oligomeric silsesquioxanes (M-POSS) were studied. The M-POSS nanocages were introduced into EA UV-curing system via copolymerization at loadings between 0% and 10 wt%. The XRD and FTIR analysis indicated that M-POSS chemically incorporated into the hybrid materials and formed a cross-linked network between M-POSS and EA. The morphological analysis showed that the discrete spherical POSS-rich particles were dispersed in the EA matrix uniformly, and both of the number and mean diameter of POSS-rich particles increased with the increasing M-POSS loadings. The influence of M-POSS on the kinetics of the photopolymerization was determined by real time FTIR spectroscopy and the result showed that the addition of POSS enhanced both of the UV-curing rates and final double bond conversion. The DMA analysis showed that increasing the amount of M-POSS nanocages caused an increase on the nanocomposite's T g . TGA curves showed that at the later period of degradation process, the thermal stability of nanocomposites was enhanced by M-POSS. With respect to the mechanical properties, the most remarkable trend was an improvement on the impact resistance of nanocomposites with the increasing POSS contents. Because both of the craze and plasticity deformation caused by POSS nanocages would absorb impact energy, hinder the growth of craze.

Flame retardancy and thermal stability of organic–inorganic hybrid resins based on polyhedral oligomeric silsesquioxanes and montmorillonite clay

Organic–inorganic hybrids were prepared by incorporation of two polyhedral oligomeric silsesquioxanes, trisilanolisobutyl POSS (TSP) and isobutylAluminum POMS (AlP), and an organoclay (OC), in an epoxy–amine system.Differential scanning calorimetry revealed the great catalytic power of AlP. OC also showed catalytic power, but to a lesser extent. The storage modulus increased with lower POSS contents, due to the nanoreinforcing effect of POSS core. At higher concentration, the modulus strongly decreases due to POSS aggregation. The glass transition temperature was barely affected by the POSS, whereas OC addition decreased it. POSS and OC supplied greater thermal stability in high temperature regions, and the char residue increased with filler concentration because silicon species are formed. POSS addition improved the flame retardancy because of a multilayered carbonaceous silicate structure formation. The presence of metal atoms in AlP composites might contribute to stabilization through secondary chemical reactions.

Thermal and Mechanical Reinforcement of Poly(Methyl Methacrylate) via Incorporation of Polyhedral Oligomeric Silsesquioxane

A series of inorganic/organic nanocomposites were prepared by blending cage-like, hydroxyl-bearing polyhedral oligomeric silsesquioxane (HO–POSS) with poly(methyl methacrylate) (PMMA) in THF solvent. Fourier transform infrared spectrophotometry (FTIR) and 29Si–nuclear magnetic resonance (29Si-NMR) were employed to characterize the structures of the HO–POSS/PMMA nanocomposites. Scanning electron microscope (SEM) images showed that the as-prepared composite films were smooth, and no severe aggregation of HO–POSS was observed when POSS content was less than 1.0 wt.%. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results showed that the incorporation of small amount of nanosized HO–POSS reinforced the thermal stability of PMMA. When 1.0 wt.% of HO–POSS was incorporated into PMMA matrix, the Tg and Td increased by 28.8 °C and 18.9 °C, respectively, due to the strong interaction between POSS cages and PMMA chains. However, higher POSS contents (&gt;2.0 wt.%) deteriorated the thermal and mechanical properties of the nanocomposites owing to the phase separation in the composite matrix caused by the aggregation of POSS cages.

Preparation and characterization of polyhedral oligomeric silsesquioxane/polystyrene nanocomposites

AbstractSeveral inorganic/organic nanocomposites were prepared via solution-blending of cage-like octahexyl-polyhedral oligomeric silsesquioxane (Oh-POSS) with polystyrene (PS) in THF solvent. FTIR and 29Si-NMR were employed to characterize the structures of the nanocomposites. SEM pictures showed that the sample films were smooth and no POSS aggregation was observed when POSS content was lower than 1.0 wt%. TGA and DSC were used to investigate the thermal property. The results showed that the incorporation of nanosized Oh-POSS enhanced the thermal stability of PS with low POSS content. When 1.0 wt% of Oh-POSS was incorporated into PS matrix, the Tg and Td increased by 7.7 °C and 8.2 °C, respectively. However, higher POSS contents (&gt;1.0 wt%) would deteriorate the thermal property of the nanocomposites due to the severe congregation of POSS..

Thermal and mechanical properties of polymethyl mathacrylate reinforced by polyhedral oligomeric silsesquioxane

AbstractA series of Inorganic/organic nanocomposites were prepared by blending cage-like carboxyl-bearing polyhedral oligomeric silsesquioxane (carboxyl-POSS) with polymethyl mathacrylate (PMMA) in THF solvent. FTIR and 29Si-NMR were employed to characterize the structures of the nanocomposites. SEM images showed that the as-prepared films were smooth and no aggregation of carboxyl-POSS was observed. TGA and DSC results showed that the incorporation of small amount of nanosize carboxyl-POSS enhanced the thermal stability of PMMA. When 1.0 wt% of carboxyl-POSS was incorporated into PMMA matrix, the Tg and Td increased by 16.9 °C and 21.0 °C, respectively. However, higher POSS contents (&gt;1.0 wt%) would deteriorate the thermal and mechanical properties of the nanocomposites.

Morphological, viscoelastic and thermal properties of poly(vinylidene Fluoride)/POSS nanocomposites

Nanocomposites of poly(vinylidene fluoride) and polyhedral oligomeric silsesquioxane were prepared through melt blending. Morphology, viscoelastic and thermal properties were investigated. Up to 1 wt.% the processing conditions were efficient to prevent formation of large POSS agglomerates. In the nanocomposites with higher POSS contents these conditions could not avoid it, because of the strong interaction among POSS molecules. The presence of two different crystalline phases in nanocomposite was evidenced by X-ray diffraction and Fourier Transformed Infra-Red Spectroscopy. The nanocomposite with 5 wt.% content had the highest values for degree of cristallinity. The polyhedral oligomeric silsesquioxane molecules are acting as lubricant in the system, once lower values for storage modulus as well as for viscosity were observed.

Synthesis of poly(4-vinylphenol) (PVPh) and polyhedral oligomeric silsesquioxanes-poly(4-vinylphenol) (POSS-PVPh) with low surface energy and their surface properties

In this paper, we have synthesized poly(4-vinylphenol) (PVPh) and polyhedral oligomeric silsesquioxanes-poly(4-vinylphenol) (POSS-PVPh) with low surface energies and investigated their surface properties. Experimental results reveal that the surface properties of PVPh and POSS-PVPh can be manipulated with the length of PVPh segment and POSS contents, respectively, resulting in the variation of intermolecular hydrogen bonding interactions. In addition, the surface energies of PVPh after thermal treatment of 180 °C for 24 h can be less than 20 mJ m −2 and those of POSS-PVPh without thermal treatment can be less than 25 mJ m −2 while those of poly(tetrafluoroethylene) (PTFE) are 22 mJ m −2.

Mechanism of Dielectric Constant Variation of POSS-Based Organic−Inorganic Molecular Hybrids

Three series of POSS containing organic−inorganic molecular hybrid low dielectric materials with different molecular architectures were prepared, in which isobutylstyryl-polyhedral oligomeric silsesquioxane (IBS-POSS) and octavinyl-polyhedral oligomeric silsesquioxane (OV-POSS) were adopted as an inorganic core to construct the pendant-type PAS-POSSpendt and star-type PAS-POSSstar hybrids, respectively. Among the organic−inorganic molecular hybrids, the POSS contents range from 0.65, 1.36, 1.62, to 3.14 in molar percentage (mol %) in PAS-POSSpendt hybrids, and from 0.36, 1.37, 2.06, to 3.72 in molar percentage (mol %) in PAS-POSSstar hybrids. Different polar organic components (organic polymeric chains) including PS, PAS, and PMMA were build into the star-type hybrids. The analysis on the relationship between molecular structure of these hybrids and their dielectric constants indicates that the incorporation of POSS molecules into the polymer matrixes will lower the dielectric constant (k) of the resulted hybrids (both pendant-type and star-type). At the same POSS content, the star-type hybrids possess a lower k than those of pendant-type ones, which is mainly assigned to the larger free volume resulted from star-type hybrids. Simultaneously, it is found that the dielectric constant of the resulting hybrids increases with the polarity of organic polymeric chain when possessing the similar molecular structure and POSS content.

Stereoregular Methacrylate-POSS Hybrid Polymers: Syntheses and Nanostructured Assemblies

This contribution reports the first examples of stereoregular (isotactic, it-, and syndiotactic, st-) methacrylate-POSS (polyhedral oligomeric silsesquioxane) hybrid polymers and their derived nanostructured assemblies. The polymerization of methyl methacrylate (MMA) by isospecific and syndiospecific living metallocene catalysts, when end-capped with methacrylisobutyl POSS (MA-POSS) or simultaneously copolymerized with MA-POSS at ambient temperature, readily produces highly stereoregular (94% it- and st-) MA-POSS end-capped PMMA (PMMA-POSS) or statistical copolymers PMMA-co-P(MA-POSS). The MA-POSS incorporation in the it-copolymers ranges from a low 2.6 mol % (20 wt %) to a high, maximum 24 mol % (75 wt %), whereas the incorporation in the st-copolymers is relatively lower with the same comonomer feed ratio due to the formation of a crystalline inclusion complex in which the POSS nanocages are encapsulated within the helical st-PMMA cavity. The it-copolymers with high POSS contents (>20 mol %) show evidence for interchain association through POSS aggregation and display a ∼20 °C Tg enhancement over the pristine it-PMMA. MA-POSS end-capped diastereomeric PMMAs exhibit versatile nanostructured assemblies, including micelle-like core−shell nanostructures (Rh up to 186 nm derived from the 5.7 nm it-PMMA-POSS unimer) through POSS inorganic collapse in selective solvents, helical stereocomplexes (Rh = 11 nm) between two or three polymer chains through organic self-organization of the diastereomeric PMMAs, and large core−shell nanospheres (Rh up to 636 nm) through synergistic organic PMMA self-organization and inorganic POSS nanocluster aggregation. Thermal annealing of the it-/st-PMMA-POSS blend in a 1:2 ratio also generates the crystalline stereocomplex with a high Tm of 213 °C.

Poly(vinyl pyrrolidone‐co‐octavinyl polyhedral oligomeric silsesquioxane) hybrid nanocomposites: Preparation, thermal properties, and Tg improvement mechanism

AbstractA series of poly(vinyl pyrrolidone‐co‐octavinyl polyhedral oligomeric silsesquioxanes) (PVP‐POSS) organic–inorganic hybrid nanocomposites containing different percentages of POSS were prepared via free radical polymerization and characterized by FTIR, high‐resolution 1H‐NMR, solid‐state 29Si‐NMR, GPC, DSC, and TGA. POSS contents in these nanocomposites can be effectively controlled by varying the POSS feed ratios which can be accurately quantified by FTIR curve calibration. On the basis of 29Si‐NMR spectra, average numbers of reacted vinyl groups of each octavinyl‐POSS macromer are calculated to be 5–7, which depends on POSS feed ratios. Both GPC and DSC results indicate that these nanocomposites display network structure and the degree of crosslinking increases with the increase of the POSS content. The incorporation of POSS into PVP significantly improves their thermal properties (Tg and Tdec) primarily due to crosslinking structure and dipole–dipole interaction between POSS cores and PVP carbonyl groups. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Preparation, Tg improvement, and thermal stability enhancement mechanism of soluble poly(methyl methacrylate) nanocomposites by incorporating octavinyl polyhedral oligomeric silsesquioxanes

AbstractThe soluble poly(methyl methacrylate‐co‐octavinyl‐polyhedral oligomeric silsesquioxane) (PMMA–POSS) hybrid nanocomposites with improved Tg and high thermal stability were synthesized by common free radical polymerization and characterized using FTIR, high‐resolution 1H NMR, 29Si NMR, GPC, DSC, and TGA. The POSS contents in the nanocomposites were determined based on FTIR spectrum, revealing that it can be effectively adjusted by varying the feed ratio of POSS in the hybrid composites. On the basis of the 1H NMR analysis, the number of the reacted vinyl groups on each POSS molecules was determined to be about 6–8. The DSC and TGA measurements indicated that the hybrid nanocomposites had higher Tg and better thermal properties than the pure PMMA homopolymer. The Tg increase mechanism was investigated using FTIR, displaying that the dipole–dipole interaction between PMMA and POSS also plays very important role to the Tg improvement besides the molecular motion hindrance from the hybrid structure. The thermal stability enhances with increase of POSS content, which is mainly attributed to the incorporation of nanoscale inorganic POSS uniformly dispersed at molecular level. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5308–5317, 2007

Preparation and thermal property of hybrid nanocomposites by free radical copolymerization of styrene with octavinyl polyhedral oligomeric silsesquioxane

AbstractThe poly(styrene‐co‐octavinyl‐polyhedral oligomeric silsesquioxane) (PS–POSS) organic–inorganic hybrid nanocomposites containing various percent of POSS were prepared via one‐step free radical polymerization and characterized by FTIR, high‐resolution 1H NMR, 29Si NMR, GPC, DSC, and TGA technologies. The POSS contents in these nanocomposites were determined using FTIR calibration curve. The result shows that the POSS contents in nanocomposites can be tailored by varying the POSS feed ratios. On the basis of the POSS contents in the nanocomposites and the 1H NMR spectra, the number of reacted vinyl groups of each octavinyl‐POSS macromonomer were calculated to be 6–8. DSC and TGA measurements indicate that the incorporation of POSS into PS homopolymer can apparently improve the thermal properties of the polymeric materials. The dramatic Tg and Tdec increases are mainly due to the formation of star and low cross‐linking structure of the nanocomposites, where POSS cores behave as the joint points and hinder the motion and degradation of the polymeric chains. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007