In situ intercalative polymerization of conducting polypyrrole/montmorillonite nanocomposites

Conducting polypyrrole (PPy)‐montmorillonite (MMT) clay nanocomposites have been synthesized by the in situ intercalative polymerization method. The PPy‐MMT nanocomposites are characterized by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis (TGA), and Fourier‐transform infrared (FTIR) spectroscopy. XRD patterns show that after polymerization by the in situ intercalative method with ammonium persulfate and 1 M HCl, an increase in the basal spacing from 1.2 to 1.9 nm was observed, signifying that PPy is synthesized between the interlayer spaces of MMT. TEM and SEM micrographs suggest that the coexistence of intercalated MMT layers with the PPy macromolecules. FTIR reveals that there might be possible interfacial interactions present between the MMT clay and PPy matrix. The study also shows that the introduction of MMT clay results in thermal stability improvement of the PPy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2279–2285, 2008     

Synthesis and properties of poly(isobutyl methacrylate‐co‐butanediol dimethacrylate‐co‐methacryl polyhedral oligomeric silsesquioxane) nanocomposites

Poly[isobutyl methacrylate‐co‐butanediol dimethacrylate‐co‐3‐methacrylylpropylheptaisobutyl‐T8‐polyhedral oligomeric silsesquioxane] [P(iBMA‐co‐BDMA‐co‐MA‐POSS)] nanocomposites with different crosslink densities and different polyhedral oligomeric silsesquioxane (MA‐POSS) percentages (5, 10, 15, 20, and 30 wt %) were synthesized by radical‐initiated terpolymerization. Linear [P(iBMA‐co‐MA‐POSS)] copolymers were also prepared. The viscoelastic properties and morphologies were studied by dynamic mechanical thermal analysis, confocal microscopy, and transmission electron microscopy (TEM). The viscoelastic properties depended on the crosslink density. The dependence of viscoelastic properties on MA‐POSS content at a low BDMA loading (1 wt %) was similar to that of linear P(iBMA‐co‐MA‐POSS) copolymers. P(iBMA‐co‐1 wt % BDMA‐co‐10 wt % MA‐POSS) exhibited the highest dynamic storage modulus (E′) values in the rubbery region of this series. The 30 wt % MA‐POSS nanocomposites with 1 wt % BDMA exhibited the lowest E′. However, the E′ values in the rubbery region for P(iBMA‐co‐3 wt % BDMA‐co‐MA‐POSS) nanocomposites with 15 and 30 wt % MA‐POSS were higher than those of the parent P(iBMA‐co‐3 wt % BDMA) resin. MA‐POSS raised the E′ values of all P(iBMA‐co‐ 5 wt % BDMA‐co‐MA‐POSS) nanocomposites in the rubbery region above those of P(iBMA‐co‐5 wt % BDMA), but MA‐POSS loadings < 15 wt % had little influence on glass‐transition temperatures (T_g's) and slightly reduced T_g values with 20 or 30 wt % POSS. Heating history had little influence on viscoelastic properties. No POSS aggregates were observed for the P(iBMA‐co‐1 wt % BDMA‐co‐MA‐POSS) nanocomposites by TEM. POSS‐rich particles with diameters of several micrometers were present in the nanocomposites with 3 or 5 wt % BDMA. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 355–372, 2005     

Synthesis of semitelechelic POSS‐polymethacrylate hybrids by thiol‐mediated controlled radical polymerization with unusual thermal behaviors

We have developed an efficient and versatile method for the synthesis of polyhedral oligomeric silsesquioxanes (POSS)‐polymethacrylate hybrids, such as POSS‐poly(methyl methacrylate) (POSS‐PMMA), POSS‐poly(ethyl methacrylate) (POSS‐PEMA), and POSS‐poly(benzyl methacrylate) (POSS‐PBzMA) of controllable molecular weights and low polydispersities by thiol‐mediated radical polymerization at elevated temperature (100 °C). By tuning the reactant concentrations and degree of polymerization of the grafted polymethacrylate chains, POSS content in these hybrid materials could be varied. MALDI‐TOF‐MS analysis of the hybrid molecule shows that the nanoscale POSS moiety is connected to the end of polymethacrylate chain through the sulfur atom bridge. These hybrid materials were further characterized using various techniques such as FTIR, XRD, NMR, TGA, and DSC. In all synthesized hybrids, the incorporation of POSS moiety at the end of polymethacrylate chain resulted in the decrease of glass transition temperature (T_g) compared to that of neat polymethacrylates of comparable molecular weights. Surprisingly, POSS‐PMMA hybrids only with relatively high POSS content (～ 10 and 16 wt %) showed physical aging behavior as reveled by DSC study. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1111–1123, 2008     

Synthesis and phase‐separation behavior of α,ω‐difunctionalized diblock copolymers

A series of diblock copolymers of n‐pentyl methacrylate and methyl methacrylate (PPMA/PMMA BCP) with one or two terminal functional groups was prepared by sequential anionic polymerization of PMA and MMA using an allyl‐functionalized initiator and/or and end‐capping with allyl bromide. Allyl functional groups were successfully converted into OH groups by hydroboration. The morphology in bulk was examined by temperature‐dependent small‐angle X‐ray measurements (T‐SAXS) and transmission electron microscopy (TEM) showing that functional groups induced a weak change in d‐spacings L₀ as well as in the thermal expansion behavior. T‐SAXS proved that the lamellar morphologies were stable over multiple heating/cooling cycles without order‐disorder transition (ODT) until 300 °C. While non‐functionalized BCP formed parallel lamellae morphologies, additional OH‐termination at the PMMA block forced in very thin films (ratio between film thickness and lamellar d‐spacing below 1) the generation of perpendicular lamellae morphology through the whole film thickness, as shown by Grazing‐incidence small‐angle X‐ray scattering experiments (GISAXS) measurements. Functionalized BCP were successfully used in thin films as templates for silica nanoparticles in an in‐situ sol–gel process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Morphology and thermal properties of polyhedral oligomeric silsesquioxane/polybutadiene nanocomposites prepared by anionic polymerization

The morphology and thermal properties of Allylisobutyl Polyhedral Oligomeric Silsesquioxane (POSS)/Polybutadiene (PB) nanocomposites prepared through anionic polymerization technique were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results of XRD, SEM and TEM showed that the aggregation of POSS in PB matrix occurred obviously, forming crystalline domains and the size of POSS particles increased with increasing POSS content. The DSC and TGA results indicated that the glass transition temperature (T _g) of the nanocomposites was significantly increased and the maximum degradation temperature (T _dmax) of nanocomposites was slightly increased compared with pure PB, implying an increase in thermal stability.     

Mussel‐inspired decoration of Ni(OH)2 nanosheets on 2D MoS2 towards enhancing thermal and flame retardancy properties of poly(lactic acid)

In the present work, a facile and environmental method was developed to fabricate the novel functionalized MoS₂ hybrid. Firstly, MoS₂ nanosheets were coated with polydopamine (PDA) through the self‐polymerization of dopamine (MoS₂‐PDA) in a buffer solution. Then the decoration of Ni(OH)₂ on the MoS₂‐PDA was synthesized because of the strong affinity of Ni²⁺ with hydroxyl groups in PDA. Finally, the as‐synthesized MoS₂‐PDA@Ni(OH)₂ was introduced into poly(lactic acid) (PLA) matrix to explore flame retardancy, thermal stability, and crystalline property of the composites. As confirmed by X‐ray diffraction (XRD), Fourier‐transform infrared spectrometer (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), the MoS₂ nanosheets were dually modified with PDA and Ni(OH)₂ without destroying the original structures. The thermal degradation of PLA with MoS₂‐PDA@Ni(OH)₂ generated a notably higher yield of char. Moreover, the crystallization rate of composites is higher than neat PLA. The cone calorimeter test revealed that the introduction of 3% MoS₂‐PDA@Ni(OH)₂ resulted in lower Peak Heat Release Rate (PHRR) (decreased by 21.7%). Thus, the research provided an innovative functionalization method for manufacturing PLA composites with high performances.     

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

The soluble poly(methyl methacrylate‐co‐octavinyl‐polyhedral oligomeric silsesquioxane) (PMMA–POSS) hybrid nanocomposites with improved T_g 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 T_g and better thermal properties than the pure PMMA homopolymer. The T_g increase mechanism was investigated using FTIR, displaying that the dipole–dipole interaction between PMMA and POSS also plays very important role to the T_g 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     

Surface energetics,dispersion, and nanotribomechanical behavior of POSS/PP hybrid nanocomposites

Hybrid organic–inorganic polymer nanocomposites incorporating polyhedral oligomeric silsesquioxane (POSS) nanoparticles are of increasing interest for high performance materials applications. Octaisobutyl POSS/polypropylene nanocomposites were prepared at varying POSS concentrations via melt blending. The interplay of POSS molecular geometry, composition, and concentration in relation to the tribological, nanomechanical, surface energy, and bulk properties of the nanocomposites were investigated. Ultra‐low friction and enhanced hardness, modulus, and hydrophobicity were observed for the nanocomposite surfaces, with minimal changes in the bulk thermomechanical properties. Parallel AFM, SEM, TEM, and spectroscopic analyses demonstrated significant differences in POSS distribution and aggregation in the surface and the bulk, with preferential segregation of POSS to the surface. Additionally, contact angle studies reveal significant reduction in surface energy and increase in hysteresis with incorporation of POSS nanoparticles. The differences in bulk and surface properties are largely explained by the gradient concentration of POSS in the polymer matrix, driven by POSS/POSS and POSS/polymer interactions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2441–2455, 2007     

Brominated poly(isobutylene‐co‐para‐methylstyrene) (BIMS)‐clay nanocomposites: Synthesis and characterization

In this work, preparation and properties of different nanoclays modified by organic amines (octadecyl amine, a primary amine, and hexadecyltrimethylammonium bromide, a tertiary amine) and brominated polyisobutylene‐co‐paramethylstyrene (BIMS)‐clay nanocomposites are reported. The clays and the rubber nanocomposites have been characterized with the help of Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). The X‐ray diffraction peaks observed in the range of 3 °–10 ° for the modified clays disappear in the rubber nanocomposites. TEM photographs show predominantly exfoliation of the clays in the range of 12 ± 4 nm in the BIMS. In the FTIR spectra of the nanocomposites, there are common peaks of virgin rubber as well as those of the clays. Excellent improvement in mechanical properties like tensile strength, elongation at break, and modulus is observed on incorporation of the nanoclays in the BIMS. Structure‐property correlation in the above nanocomposites is attempted. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4489–4502, 2004     

Miscibility,specific interactions,and self‐assembly behavior of phenolic/polyhedral oligomeric silsesquioxane hybrids

The miscibility of a phenolic resin with polyhedral oligomeric silsesquioxane (POSS) hybrids and the specific interactions between them were investigated with Fourier transform infrared (FTIR) spectroscopy and wide‐angle X‐ray diffraction (WAXD). An analysis of the morphology and microstructure was performed with polarized optical microscopy and atomic force microscopy (AFM). The interassociation equilibrium constant between the phenolic resin and POSS (38.7) was lower than the self‐association equilibrium constant of pure phenolic (52.3) according to the Painter–Coleman association model. This result indicated that POSS was partially miscible with the phenolic resin. A polarized optical microscopy image of a phenolic/POSS hybrid material (20 wt % POSS) indicated that the crystals of POSS were arranged evenly in the phenolic matrix; the self‐assembled array of POSS crystals was also confirmed by AFM. This phenomenon was consistent with the FTIR spectroscopy and WAXD analyses. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1127–1136, 2004     

Thermally curable organic/inorganic hybrid polymers as gate dielectrics for organic thin‐film transistors

New low‐temperature curable organic/inorganic hybrid polymers were designed and synthesized as gate dielectrics for organic thin‐film transistors (OTFTs). Allyl alcohols were introduced to polyhedral oligomeric silsesquioxane (POSS) via hydrosilyation to produce an alcohol‐functionalized POSS derivative (POSS‐OH). POSS‐OH was then reacted with hexamethoxymethylmelamine at carrying molar ratios at 80 °C in the presence of a catalytic amount of p‐toluenesulfonic acid to give highly cross‐linked network polymers (POSS‐MM). The prepared thin films were smooth and hard after the thermal cross‐linking reaction and had very low leakage currents (<10^?8 A/cm²) with no significant absorption over the visible spectral range. Pentacene‐based OTFTs using the synthesized insulators as gate dielectric layers had higher hole mobilities (up to 0.36 cm²/Vs) than a device using thermally cross‐linked poly(vinyl phenol) and melamine as the gate dielectric layer (0.18 cm²/Vs). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3260–3268     

Nitrogen‐doped graphene‐cerium oxide (NG‐CeO2) photocatalyst for the photodegradation of methylene blue in waste water

This study shows a facile approach for the preparation of CeO₂ nanoparticles decorated with porous nitrogen‐doped graphene (NG) nanosheets for effective photocatalytic degradation of methylene blue (MB). NG nanosheets were first synthesized using a hydrothermal method and then nitrogen‐doped graphene‐cerium oxide (NG‐CeO₂) was prepared through mixing of cerium nitrate with different concentrations of NG under ultrasonication followed by hydrothermal treatment. The synthesized nanocomposites were characterized using X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE‐SEM). The photocatalytic activity of the synthesized nanocomposites was analyzed against MB dye. Results showed that the nanocomposites of NG‐CeO₂ have an average particle size of 20 nm. The as‐prepared NG‐CeO₂ nanocomposites exhibited outstanding photocatalytic activity for dye degradation under visible light irradiation, which could be attributed to synergistic effects between the NG nanosheets and CeO₂. The quantum of photodegradation increases with the increase of the NG content in the nanocomposites.     

Novel polymer nanocomposites based on polystyrene and Ti‐functionalized polyhedral silsesquioxanes

Ti‐based polyhedral silsesquioxanes (Ti‐POSSs) have been prepared and dispersed in polystyrene (PS), by in situ polymerization, and the resulting materials have been characterized by several experimental techniques including both scanning (SEM) and transmission (TEM) electron microscopy, wide angle X‐ray diffraction (WAXD), X‐ray photospectroscopy (XPS), and thermogravimetric analysis (TGA/DTG). TEM and SEM analyses proved that PS nanocomposites of the samples based on heptaisobutyl‐Ti‐POSS (HEI‐Ti‐POSS) are formed, where HEI‐Ti‐POSS cages are directly linked to the macromolecules via Ti‐C bonds. The presence of HEI‐Ti‐POSS enhances the thermo‐oxidative stability of PS‐based nanocomposites and does not significantly affect the polymer molecular mass. Copyright © 2009 John Wiley & Sons, Ltd.     

POSS‐nylon 6 nanocomposites: Influence of POSS structure on surface and bulk properties

Hybrid organic/inorganic nanocomposites based on polyhedral oligomeric silsesquioxane (POSS) nanostructured chemicals and nylon 6 were prepared via melt mixing. Two structurally and chemically different POSS molecules, a closed cage, nonpolar octaisobutyl POSS (Oib‐POSS) and an open cage, polar trisilanolphenyl POSS (Tsp‐POSS) with differing predicted solubility parameters were evaluated in the nylon matrix. Surface analysis, including quasi‐static and dynamic nanoindentation and nanotribological techniques, revealed exceptional improvements in modulus and hardness along with significant reductions in friction. Additionally, surface wetting characteristics of the nylon were reversed, with POSS incorporation yielding low surface energy, highly hydrophobic surfaces. AFM, TEM/EDAX, spectroscopic techniques and thermomechanical analysis were used to evaluate nanoscale dispersion and bulk properties of the composites. Both POSS molecules exhibit preferential surface segregation behavior in the nylon matrix. Tsp‐POSS, with its higher predicted solubility in nylon, exhibited enhanced dispersion and tribomechanical properties at both nano and bulk scale. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1088–1102, 2009     

A hybrid‐type,chiral π‐conjugated polymer wrapped with polyhedral oligomeric silsesquioxanes

A novel hybrid‐type chiral binaphthyl‐based polyarylene derivative with polyhedral oligomeric silsesquioxanes (POSS) units 2a was prepared by Suzuki–Miyaura coupling polymerization from a chiral (R)‐6,6′‐dibromo‐2,2′‐diPOSS‐substituted 1,1′‐binaphthyl derivative 1a and p‐biphenylene diboronic acid. As a reference, a binaphthyl‐based polyarylene derivative without POSS unit 2b was also prepared. The obtained polymers were studied with thermogravimetric analysis, optical rotations, circular dichroism (CD), ultraviolet‐visible, and photoluminescence (PL) spectra. Gel permeation chromatography measurements of 2a and 2b showed that their number‐average molecular weights were 13,300 and 16,500, respectively. The thermal stability of POSS‐modified polymer 2a (temperature of 10% weight loss; T₁₀ = 380 °C) was extremely high compared with that of polymer without POSS unit 2b (T₁₀ = 335 °C) due to the siliceous bulky POSS segments on the side chains. The specific optical rotation [α]_D was ?66.7° (c 0.06, CHCl₃) for 2a and ?62.3° (c 0.06, CHCl₃) for 2b . The CD spectra showed that these two polymers had very similar and strong Cotton effects. Film polymer 2a showed almost the same PL spectrum as that in dilute CHCl₃ solution, indicating that bulky POSS units strongly suppressed intermolecular aggregation of the π‐conjugated polymer backbone. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6035–6040, 2008     

Poly(methyl methacrylate)/Methacryl-POSS Nanocomposites with Excellent Thermal Properties

Poly(methyl methacrylate) (PMMA) nanocomposites containing (methacryloxy)propyl polyhedral oligomeric silsesquioxane (methacryl‐POSS) were prepared by bulk‐polymerization process. The structures of the products were characterized by FTIR, solid‐state NMR, TEM, XRD, DSC, TGA, XPS and UV‐Vis spectra. The hybrid materials were found to be largely homogeneous. DSC and TGA results indicate that the thermal properties of PMMA nanocomposites are significantly improved. The glass transition temperature (T_g) and thermal decomposition temperature (T_dec) of the nanocomposites increased by 58 and 110°C, respectively. The bulk hybrid material maintains excellent optical transparency in visible region.     

Synthesis,characterization, and properties of monodispersed magnetite coated multi‐walled carbon nanotube/polypyrrole nanocomposites synthesized by in‐situ chemical oxidative polymerization

This study describes the preparation of a nanocomposites fabricated from monodispersed 4‐nm iron oxide (Fe₃O₄) coated on the surface of carboxylic acid containing multi‐walled carbon nanotube (c‐MWCNT) and polypyrrole (PPy) by in situ chemical oxidative polymerization. High‐resolution transmission electron microscopy images and X‐ray diffraction (XRD) data indicate that the resulting Fe₃O₄ nanoparticles synthesized using the thermal decomposition are close to spherical dots with a particle size about 4 ± 0.2 nm. The resulting nanoparticles were further mixed with c‐MWCNT in an aqueous solution containing with anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate to form one‐dimensional Fe₃O₄ coated c‐MWCNT template for further preparation of nanocomposite. Structural and morphological analysis using field‐emission scanning electron microscopy, high‐resolution transmission electron microscopy, and XRD showed that the fabricated Fe₃O₄ coated c‐MWCNT/PPy nanocomposites are one‐dimensional core (Fe₃O₄ coated c‐MWCNT)‐shell (PPy) structures. The conductivities of these Fe₃O₄ coated c‐MWCNT/PPy nanocomposites are about four times higher than those of pure PPy matrix. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 727–733, 2008     

Polymerization and nanocomposites properties of multifunctional methylmethacrylate POSS

Thermally induced polymerization of multifunctional methylmethacrylate POSS (MMA‐POSS) was studied in this work for preparation of polymer/POSS nanocomposites. The polymerization of MMA‐POSS could be promoted with benzoyl peroxide (BPO). Self‐assembly of POSS into a layer‐by‐layer structure in the MMA‐POSS polymer (TP‐MMA‐POSS) is observed with a transmission electron microscopy. An ultra‐low‐k value of about 1.85 is measured with TP‐MMA‐POSS. In addition, polyimide‐POSS nanocomposites are also prepared. These nanocomposites demonstrate good homogeneity and enhanced mechanical properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5157–5166, 2008     

Preparation and properties of polyhedral oligosilsequioxane tethered aromatic polyamide nanocomposites through Michael addition between maleimide‐containing polyamides and an amino‐functionalized polyhedral oligosilsequioxane

Polyhedral oligosilsequioxane (POSS) tethered aromatic polyamide nanocomposites with various POSS fractions were prepared through Michael addition between maleimide‐containing polyamides and amino‐functionalized POSS. The chemical structures of the polyamide–POSS nanocomposites were characterized with Fourier transform infrared and ¹H NMR. The polyamide–POSS nanocomposites exhibited good homogeneity in scanning electron microscopy and transmission electron microscopy observations. POSS modification increased the storage modulus and Young's modulus of the polyamides, slightly decreased their glass‐transition temperatures from 312 to 305 °C, and significantly lowered their dielectric constants from 4.45 to 3.35. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4632–4643, 2006     

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.