Flame‐retardant epoxy resins: An approach from organic–inorganic hybrid nanocomposites

Phosphorus‐containing epoxy‐based epoxy–silica hybrid materials with a nanostructure were obtained from bis(3‐glycidyloxy)phenylphosphine oxide, diaminodiphenylmethane, and tetraethoxysilane in the presence of the catalyst p‐toluenesulfonic acid via an in situ sol–gel process. The silica formed on a nanometer scale in the epoxy resin was characterized with Fourier transform infrared, NMR, and scanning electron microscopy. The glass‐transition temperatures of the hybrid epoxy resins increased with the silica content. The nanometer‐scale silica showed an enhancement effect of improving the flame‐retardant properties of the epoxy resins. The phosphorus–silica synergistic effect on the limited oxygen index (LOI) enhancement was also observed with a high LOI value of 44.5. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 986–996, 2001     

Enhanced efficiency of polyfluorene derivatives: Organic–inorganic hybrid polymer light‐emitting diodes

Two novel organic–inorganic hybrid polyfluorene derivatives, poly{(9,9′‐dioctyl‐2,7‐fluorene)‐co‐(9,9′‐di‐POSS‐2,7‐fluorene)‐co‐[2,5‐bis(octyloxy)‐1,4‐phenylene]} (PFDOPPOSS) and poly{(9,9′‐dioctyl‐2,7‐fluorene)‐co‐(9,9′‐di‐POSS‐2,7‐fluorene)‐co‐bithiophene} (PFT2POSS), were synthesized by the Pd‐catalyzed Suzuki reaction of polyhedral oligomeric silsesquioxane (POSS) appended fluorene, dioctyl phenylene, and bithiophene moieties. The synthesized polymers were characterized with ¹H NMR spectroscopy and elemental analysis. Photoluminescence (PL) studies showed that the incorporation of the POSS pendant into the polyfluorene derivatives significantly enhanced the fluorescence quantum yields of the polymer films, likely via a reduction in the degree of interchain interaction as well as keto formation. Additionally, the blue‐light‐emitting polyfluorene derivative PFDOPPOSS showed high thermal color stability in PL. Moreover, single‐layer light‐emitting diode devices of an indium tin oxide/poly(3,4‐ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration fabricated with PFDOPPOSS and PFT2POSS showed much improved brightness, maximum luminescence intensity, and quantum efficiency in comparison with devices fabricated with the corresponding pristine polymers PFDOP and PFT2. In particular, the maximum external quantum efficiency of PFT2POSS was 0.13%, which was twice that of PFT2 (0.06%), and the maximum current efficiency of PFT2POSS was 0.38 cd/A, which again was twice that of PFT2 (0.19 cd/A). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2943–2954, 2006     

Physical and electronic properties in multiwalled carbon nanotube–poly(3‐dodecylthiophene) nanocomposites

The properties of nanocomposites of dodecyl ester functionalized multiwalled carbon nanotube (FMWNT) and four poly(3‐dodecyl thiophene) (P3DDT) samples with different molecular weight and chain regioregularity are reported here. Uniform dispersion of FMWNT in the composites is evident from TEM study. π–π and CH–π interactions are evident from FTIR spectra in the low molecular weight (M_w = 8 × 10⁴) and high regiorandom (head‐tail = 69 mol %) P3DDT (ILM) composites; however, such interactions are not so prominent for other P3DDTs. Wide‐angle X‐ray scattering patterns indicate intact interchain lamellar structure of P3DDT in the composites. DSC study shows decrease of main chain melting peak of P3DDT (ILM) with increasing F‐MWNT content but the decrease is lower with higher molecular weight and higher regioregular samples. Dynamic mechanical analyzer study indicates that there is no significant change in the T_g, T_β, and T_γ transition temperature with FMWNT concentration indicating almost ideal mixing of the components. The percent increase of G′ increases with increasing FMWNT loading and also with temperature showing an 84% increase in storage modulus at –20 °C for ILM12 samples. The UV–vis spectrum indicates a decrease in band gap with FMWNT concentration for ILM composites, however, it is negligible with other P3DDTs. Photoluminescence quenching and multiple emission peaks occur in the composites. dc‐Conductivity of the composites increases by two orders and current‐voltage (I–V) curves show memory effect only in ILM‐MWNT composites. The I–V curves of other P3DDT nanocomposites exhibit rectification property. Quantitative explanation of electronic properties has been afforded from the band energy and work function values. So, the electronic properties of the nanocomposite can be tuned by changing the molecular weight, regioregularity, and concentration of FMWNT. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1412–1425, 2009     

Structure and coordination of organometallic groups on a chemically modified SiO2 surface

The structural, electronic, and energy parameters of the metal-containing clusters (H₃SiO)₃Si−O−XMe _n (X=H, B, Al, or Zn;n=0, 1, or 2), which model organometallic groups on a SiO₂ surface modified with B-, Al-, and Zn-containing alkyls, have been studied by quantum-chemical methods. Full geometry optimization for these clusters was carried out by the SCF MO LCAO method taking into account the electron correlation within the frameworks of the MP2 and B3LYP schemes using the 6-31G(d) (6-311G(d) for Zn) basis set. The effect of the crystal environment was taken into account in calculations of siliconoxygen clusters containing 10 and 30 silicon atoms using theab initio SCF/6-31G(d) and semiempirical MNDO-PM3 methods. Various modes of coordination and interactions of organometallic groups with oxygen atoms of surface groups were studied. For the organoaluminum group on the surface, two stable conformations were found, namely, the three-coordinate structure with the chain −O−AlMe₂ ligand and the four-coordinate (quasicyclic) structure with the Al atom that forms two nonequivalent bonds with the O atoms at the same Si atom. The four-coordinate structure is energetically more favorable. No stable structures were found for the organoboron and organozinc fragments. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1296–1303, July, 1998.     

Influence of hybrid system of nanofillers on the functional properties of postconsumer PET‐G–based nanocomposites

In this article, postconsumer poly (ethylene glycol‐co‐1,4‐cyclohexanedimethanol terephthalate) (PET‐G) foils have been modified with three types of carbon nanofillers that differ in size and shape, ie, multiwalled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNP), and nanosized carbon black (nCB), thus enabling the reusage of recyclate in receiving new functional materials. The series of polymer hybrid nanocomposites have been prepared via a two‐stage polycondensation process, be means of glycolysis of postconsumer PET‐G foil, followed by polycondensation in the presence of carbon nanofillers. The scanning electron microscopy revealed that nanoadditives were uniformly dispersed into the whole volume of polymer matrix. The results present the synergistic effect of hybrid system of nanofillers in improving tensile properties of PET‐G. It has been found that the incorporation of three types of carbon nanofillers has not affected the glass transition temperature of the polymer matrix. Moreover, the incorporation of carbon nanofillers, and the mixture of two, or even three of those, caused an improvement in thermal conductivity and thermal stability.     

Construction of a TiO2–Fe3O4‐decorated molecularly imprinted polymer nanocomposite for tartrazine degradation: Response surface methodology modeling and optimization

We synthesized a novel recoverable and reusable photocatalyst system for tartrazine degradation by one‐step incorporation of Fe₃O₄ and TiO₂ nanoparticles into a molecularly imprinted polymer through a facile precipitation polymerization method. The as‐prepared samples were systematically characterized using X‐ray diffraction, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy‐dispersive spectroscopy, and vibrating sample magnetometry. Benefiting from the positive synergistic effect, tartrazine was almost completely degraded under UV‐C within 180 min by the multicomponent photocatalyst (Fe₃O₄ + TiO₂ + MIP) in comparison with far fewer activities by the corresponding NIP system and the nonmagnetic and bare structures. On the other hand, the central composite design in response surface methodology was applied to optimize the tartrazine photocatalytic degradation process. Twenty experiments were conducted by adjusting three parameters (nanocomposite dosage, initial pH of the reaction solution, and initial dye concentration) in the multiple variable analysis method. A satisfactory correlation between the experimental and predicted values was obtained (R² = 0.956). Additionally, ANOVA analysis with a p value of 1.15 × 10^–5 indicated that the model terms are highly significant. Under the determined optimum conditions, a verification experiment was conducted and shown the adequately approximate value between the predicted (99%) and the experimental (97%) results, which confirmed the validity of the model.     

Montmorillonite‐based nanocomposites of polybenzoxazole: Synthesis and characterization (I)

Poly(amic acid) was synthesized by means of low‐temperature‐solution polymerization of 3,3′‐dihydroxybenzidine and pyromellitic dianhydride in N,N‐dimethylacetamide. The precursor polymer was heat‐treated at different temperatures to create a polybenzoxazole (PBO) through a polyimide (PI). PI containing the hydroxyl group was rearranged by decarboxylation with heat treatment, resulting in a fully aromatic PBO. Hexadecylamine was used as an organophilic alkylamine in organo‐clay. We have tried to clarify the intercalation of heterocyclic polymer chains to hexadecylamine–montmorillonite (C₁₆‐MMT) and improve tensile properties. It was found that the addition of only a small amount of organo‐clay was enough to improve the mechanical properties of PBO. Maximum enhancement in the ultimate tensile strength for PBO hybrids was observed for the blends containing 4% C₁₆‐MMT. The initial modulus monotonically increased with further increases in the C₁₆‐MMT content. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 471–476, 2001     

Large‐scale extrusion processing and characterization of hybrid nylon‐6/SiO2 nanocomposites

Solution impregnations, pulltrusion and film stacking are widely used methods to prepare thermoplastic composite materials. Extruders are used to melt the polymer and to incorporate fibers into the polymer in order to modify physical properties. In this article, the compounding of colloidal silica nanoparticles filled polyamide‐6 (PA‐6) is achieved using a twin‐screw extruder, which has a significant market share due to its low cost and easy maintenance. The experiments were performed at 250 rpm and the bulk throughput was 6 kg h^?1 with a pump pressure of 30 bars. The composites were characterized with nuclear magnetic resonance (NMR), wide angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). As determined by WAXD, the PA‐6 showed higher amounts of γ‐phase when compared to other synthesis methods such as in situ polymerization. TEM pictures showed that the silica particles aggregated nevertheless, upon addition of 14% (w/w) silica the E‐modulus increased from 2.7 to 3.9 GPa indicating that an effective mechanical coupling with the polymer was achieved. The behavior, illustrated with dynamic mechanical analysis (DMA) curves, indicated that in general when a filled system is compared to unfilled material, the values of the moduli (E′ and E″) increased and tan δ decreased. Determination of molecular mass distribution of the samples by means of size exclusion chromatography (SEC) coupled to a refractive index (RI), viscosity (DV) and light scattering (LS) detector revealed that the addition of silica did not decrease the average molecular weight of the polymer matrix, which is of importance for composite applications. Copyright © 2004 John Wiley & Sons, Ltd.     

Investigation of clay modifier effects on the structure and rheology of supercritical carbon dioxide‐processed polymer nanocomposites

Superior property enhancements in polymer–clay nanocomposites can be achieved if one can significantly enhance the nanoclay dispersion and polymer–clay interactions. Recent studies have shown that nanoclays can be dispersed in polymers using supercritical carbon dioxide (scCO₂). However, there is need for a better understanding of how changing the clay modifier affects the clay dispersability by scCO₂ and the resultant nanocomposite rheology. To address this, the polystyrene (PS)/clay nanocomposites with “weak” interaction (Cloisite 93A clay) and “strong” interaction (Cloisite 15A clay) have been prepared using the supercritical CO₂ method in the presence of a co‐solvent. Transmission electron microscopy images and small‐angle X‐ray diffraction illustrate that composites using 15A and 93A clays show similar magnitude of reduction in the average tactoid size, and dispersion upon processing with scCO₂. When PS and the clays are coprocessed in scCO₂, the “dispersion” of clays appears to be independent of modifier or polymer–clay interaction. However, the low‐frequency storage modulus in the scCO₂‐processed 15A nanocomposites is two orders of magnitude higher than that of 93A nanocomposites. It is postulated that below percolation (solution blended composites), the strength of polymer–clay interaction is not a significant contributor to rheological enhancement. In the scCO₂‐processed nanocomposites the enhanced dispersion passes the percolation threshold and the interactions dictate the reinforcement potential of the clay–polymer–clay network. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 823–831, 2010     

Highly efficient CO2 capture with a metal–organic framework‐derived porous carbon impregnated with polyethyleneimine

Global warming is considered as one of the great challenges of the twenty‐first century. Application of CO₂ capture and storage technologies to flue gas is considered to be a useful method of lessening global warning. Highly porous carbon has played an important role in tackling energy and environmental problems. We attempted to synthesize a highly porous carbon adsorbent by carbonizing a highly crystalline metal–organic framework (MOF) without any carbon precursors and focused on the adsorption of CO₂ and CH₄ gases and CO₂/CH₄ selectivity at 298, 323 and 348 K using a volumetric apparatus. The MOF‐derived porous carbon (MDC) was prepared by direct carbonization of MOF‐199 as a template at 900 °C under nitrogen atmosphere. Amino‐impregnated MDC samples exhibited enhanced adsorption capacities by a combination of physical and chemical adsorption. Polyethyleneimine (PEI) was selected as the amine source, which was found to greatly enhance CO₂ capture when supported on the porous carbon. Novel PEI‐impregnated MDC nanocomposites were synthesized by wetness impregnation and then characterized using various methods.     

Ionic liquid‐based organic–inorganic hybrid electrolytes: Impact of in situ obtained and dispersed silica

Organic–inorganic hybrid electrolytes based on PEO‐NaTFSI‐ionic liquid (HMIMTFSI)‐silica (in situ production via sol gel process) are being reported in this article. The variation in conductivity with ionic liquid (IL) addition has been explained on the basis of number of free TFSI anions evaluated using ATR‐IR data. The deconvolution of the IR spectra of these hybrid electrolytes has given evidence of ion‐pair formation which has been compared vis‐á‐vis the conductivity variation. The hybrid electrolyte with maximum conductivity comprises the highest number of free imide ions and has lowest glass transition temperature. FESEM has displayed a porous and layered surface morphology with dispersed silica nanoparticles. In addition, the optimized hybrid electrolyte has been compared with 5 wt% (limit of mechanical stability) ex situ silica added composite where the temperature cycling of conductivity has shown that the ex situ dispersed hybrid electrolytes do not retrace their conductivity path contrary to the in situ prepared hybrid electrolytes. This behavior has been explained to be due to the hindrance offered by the ex situ added silica in the recrystallization kinetics of PEO. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 207–218     

Grafting of polymers onto and/or from silica surface during the polymerization of vinyl monomers in the presence of γ‐ray‐irradiated silica

The effects of radicals on silica surface, which were formed by γ‐ray irradiation, on the polymerization of vinyl monomers were investigated. It was found that the polymerization of styrene was remarkably retarded in the presence of γ‐ray‐irradiated silica above 60 °C, at which thermal polymerization of styrene is readily initiated. During the polymerization, a part of polystyrene formed was grafted onto the silica surface but percentage of grafting was very small. On the other hand, no retardation of the polymerization of styrene was observed in the presence of γ‐ray‐irradiated silica below 50 °C; the polymerization tends to accelerate and polystyrene was grafted onto the silica surface. Poly(vinyl acetate) and poly(methyl methacrylate) (MMA) were also grafted onto the surface during the polymerization in the presence of γ‐ray‐irradiated silica. The grafting of polymers onto the silica surface was confirmed by thermal decomposition GC‐MS. It was considered that at lower temperature, the grafting based on the propagation of polystyrene from surface radical (“grafting from” mechanism) preferentially proceeded. On the contrary, at higher temperature, the coupling reaction of propagating polymer radicals with surface radicals (“grafting onto” mechanism) proceeded to give relatively higher molecular weight polymer‐grafted silica. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2972–2979, 2006     

Organic–inorganic nanocomposites of (2‐hydroxypropyl)cellulose as a precursor of nanocrystalline zinc oxide layers

The sol–gel method of synthesis of the hybrid nanocomposite films of ZnO/(2‐hydroxypropyl) cellulose (HPC) on silica glass is presented. The sol phases were prepared for different weight ratios of zinc acetate dihydrate to HPC in the presence of triethylamine (TEA). Raman spectrum of the mixture of ZnAc and HPC indicates coordinating interaction between zinc ion and HPC. The generation of ZnO nanoparticles in the HPC matrix proceeds in situ through the annealing of the gel phase at a temperature of 160°C. Identification of ZnO nanoparticles in the HPC matrix is done by using photoluminescence (PL), UV–Vis, and Raman spectroscopy. The films of ZnO/HPC nanocomposite are transparent in the visible light and show a higher energy value of absorption edge compared with ZnO in the bulk. Nanocrystalline films of ZnO were obtained by the calcination of ZnO/HPC nanocomposite at 500°C. ZnO films possess a good transparency for the visible light and high absorbance for UV light. Nanocrystallite sizes of ZnO particles were estimated from the X‐ ray lines broadening. The properties of ZnO layers were studied by the evaluation of PL, X‐ray investigation and atom force microscope (AFM) scanning, and the optical absorption edge. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation,characterization, and properties of novolac‐type phenolic/SiO2 hybrid organic–inorganic nanocomposite materials by sol–gel method

This article describes the preparation of novolac‐type phenolic resin/silica hybrid organic–inorganic nanocomposite, with a sol–gel process. The coupling agent was used to improve the interface between the organic and inorganic phases. The effect of the structure of the nanocomposite on its physical and chemical properties is discussed. The coupling agent reacts with the resin to form covalent bonds. The structure of the modified hybrid nanocomposites was identified with a Fourier transform infrared spectroscope. The silica network was characterized by nuclear magnetic resonance imaging (²⁹Si NMR). Results revealed that Q₄ (tetrasubstituted) and T₃ (trisubstituted) are the dominant microstructures. The size of the silica in the phenolic resin was characterized with a scanning electron microscope. The size of the particles of inorganic silica in the modified system was less than 100 nm. The nanocomposite exhibited good transparency. Moreover, the thermal and mechanical properties exhibited significant improvement. The modified hybrid composite exhibited favorable thermal properties. The temperature at which a weight loss of 5% occurred increased from 281 to 350 °C. The flexural strength increased by 6–30%. The limiting oxygen index of the nanocomposite reached 37, and the Underwriters Laboratory test was 94V‐0. Consequently, these materials possess excellent flame‐retardant properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 905–913, 2003     

An organic–inorganic hybrid compound containing imidazolium cations and a one‐dimensional lithium hexacyanidocobaltate‐based anionic framework

An organic–inorganic hybrid compound, catena‐poly[bis(3H‐imidazol‐1‐ium) [[tetracyanido‐κ⁴C‐cobalt(III)]‐μ‐cyanido‐κ²C:N‐[diaqualithium(I)]‐μ‐cyanido‐κ²N:C]], {(C₃H₅N₂)₂[CoLi(CN)₆(H₂O)₂]}_n, was synthesized by the reaction of Li₃[Co(CN)₆] with imidazolium chloride in aqueous solution. The compound crystallizes in the monoclinic space group C2/c (data collected at 273 K). In the crystal structure, neighbouring [Co(CN)₆]³⁻ anionic units are linked by Li⁺ cations through the cyanide groups in a trans mode, forming a one‐dimensional zigzag chain structure extending along the c axis. A three‐dimensional supramolecular network is formed through hydrogen‐bonding interactions and is further stabilized by weak CN...π interactions between the cyanide groups and the imidazolium cations.     

Gold‐loading magnetic core–shell organic/inorganic nanocomposites: facile preparation and multiple properties

Magnetic composite nanospheres (MCS) were first prepared via mini‐emulsion polymerization. Subsequently, the hybrid core–shell nanospheres were used as carriers to support gold nanoparticles. The as‐prepared gold‐loading magnetic composite nanospheres (Au‐MCS) had a hydrophobic core embed with γ‐Fe₃O₄ and a hydrophilic shell loaded by gold nanoparticles. Both the content of γ‐Fe₃O₄ and the size of gold nanoparticles could be controlled in our experiments, which resulted in fabricating various materials. On one hand, the Au‐MCS could be used as a T₂ contrast agent with a relaxivity coefficient of 362 mg^?1 ml S^?1 for magnetic resonance imaging. On the other hand, the Au‐MCS exhibited tunable optical‐absorption property over a wavelength range from 530 nm to 800 nm, which attributed to a secondary growth of gold nanoparticles. In addition, dynamic light scattering results of particle sizing and Zeta potential measurements revealed that Au‐MCS had a good stability in an aqueous solution, which would be helpful for further applications. Finally, it showed that the Au‐MCS were efficient catalysts for reductions of hydrophobic nitrobenzene and hydrophilic 4‐nitrophenol that could be reused by a magnetic separation process. Copyright © 2014 John Wiley & Sons, Ltd.     

Organic–inorganic hybrid membranes prepared from the sol–gel process of poly(butyleneadipate‐co‐terephthalate) and TiO2

Organic–inorganic hybrids based on poly(butyleneadipate‐co‐terephthalate)/titanium dioxide (PBAT/TiO₂) hybrid membranes were prepared via a sol–gel process. The PBAT/TiO₂ hybrid membranes were prepared for various PBAT/TiO₂ ratios. The resulting hybrids were characterized with a morphological structure, hydrophilicity, biodegradability, and thermal properties. The results showed that macrovoids underwent a transition into a sponge‐like membrane structure with the addition of TiO₂. After sol–gel transition, a strong interaction between the inorganic network and polymeric chains led to an increase in glass transition temperature (T_g), thermal degrading temperature, and hydrophilicity, and hence a higher biodegradability. According to X‐ray diffraction measurements of the crystal structure of the hybrid, the presence of TiO₂ did not change the crystal structure of PBAT. TiO₂ networks are uniformly dispersed into the PBAT matrix and no aggregation of TiO₂ networks in the hybrid membranes was observed through the small angle X‐ray scattering measurements. Thus, the sol–gel process of PBAT and TiO₂ can be used to prepare a hybrid with higher application temperature and faster biodegradation rate. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis of hydrophilic polymers in supercritical carbon dioxide in the presence of a siloxane‐based macromonomer surfactant: Heterogeneous polymerization of 1‐vinyl‐2 pyrrolidone

Batch free radical polymerization of 1‐vinyl‐2‐pyrrolidone (VP) in supercritical carbon dioxide (scCO₂) was studied in the presence of a reactive polysiloxane surfactant (PDMS‐mMA). Phase behavior investigation showed that when the initial concentration of the surface active macromonomer was higher than 2.5% w/w with respect to the monomer, the reaction mixture, in the absence of efficient stirring, was initially opaque to the visible light, and it slowly turned to an orange tint. Polymerization experiments carried out with surfactant concentration higher than the aforementioned value proceeded with a fast kinetics, and led to the formation of spherical nanoparticles with almost quantitative yields (higher than 98% with a reaction time lower than 70 min). The effect of the concentration of the surface active macromonomer, the initiator and the monomer, and of the density of the fluid phase on the kinetics of the process and on the morphology of the particles was investigated. A marked decrease of the number‐average diameter of the polymer particles with the surfactant concentration was obtained without any particle agglomeration. A dependence on [Initiator]^?0.16 of the particle diameter was observed. Such scaling law exhibits an exponent higher than any previously reported for dispersion processes and rather close to those foreseeable on the basis of Smith–Harkins kinetics for emulsion polymerization. Collected experimental results strongly suggest that the polymerization of VP in the presence of PDMS‐mMA could proceed with a nucleation mechanism different from that postulated in pure dispersion polymerization stabilized by graft‐forming surfactants. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 173–185, 2004     

Synthesis and optical properties of organic–inorganic hybrid semi‐interpenetrating polymer network gels containing polyfluorenes

Organic–inorganic hybrid semi‐interpenetrating polymer network (semi‐IPN) gels containing polyfluorenes (PFs) are synthesized by hydrosilylation reaction of joint and rod molecules in toluene, where PFs are poly(9,9‐dihexylfluorene‐2,7‐diyl) (PF6) or, poly(9,9‐dioctylfluorene‐2,7‐diyl) (PF8), joint molecules are 1,3,5,7‐tetramethylcyclotetrasiloxane (TMCTS), or 1,3,5,7,9,11,13,15‐octakis(dimethylsilyloxy)pentacyclo‐[9,5,1,1,1,1]octasilsesquioxane (POSS), and rod molecules are 1,5‐hexadiene (HD) or 1,9‐decadiene (DD). The semi‐IPN gels containing low molecular weight PF6 show higher photoluminescence efficiency (?_g) than the toluene solution of PF6L (?_s). The semi‐IPN gels composed of long rod molecule of DD and cubic joint molecule of POSS show the most effective increase in the emission intensity. The emission intensity of PF6L increases as formation of the network in the POSS‐DD semi‐IPN gel. The POSS‐DD semi‐IPN gels containing high molecular weight PF6 and PF8 also show the increase of emission intensity than those of the toluene solutions. The semi‐IPN synthesized in cyclohexane show syneresis and phase separation between network structure and PF chains. The semi‐IPN gels containing PF8 show emission peaks at 450 and 470 nm derived from β‐sheet structure of PF8. A systematic study clears correlation between emission property and network structure and/or composition of semi‐IPN gels. The semi‐IPN gels provide emissive self‐standing soft materials with high efficiency and in a narrow wavelength range emission. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 973–984     

Moisture‐resistant and strength retention properties of supercritical CO2‐processed thermoplastic starch modified by polyvinyl alcohol with varying degrees of polymerization

The ease of melt‐processing, moisture‐resistance, and tensile retention properties of scCO₂ and polyvinyl alcohol (PVA)–modified thermoplastic starch (scCO₂TPS_xPVA^a_y) materials were explored in this investigation. These characteristics were considerably improved by PVA modification particularly with decreasing PVA degree of polymerization (DP). The intensities of O―H stretching bands of scCO₂TPS_xPVA^a_y were considerably larger, and peak location of O―H stretching bands were significantly smaller than those of the corresponding TPS_xPVA^a_y and reduced gradually with the decrease in PVA's DP. The ΔH of melting and diffraction peaks of V_h‐type crystals for conditioned TPS_xPVA^a_y and scCO₂TPS_xPVA^a_y were considerably smaller than those of corresponding TPS and TPS_xPVA^a_y aged for the same time period and gradually reduced in intensity with decreasing PVA's DP. Possible reasons accounting for the considerably improved melt processing, moisture resistance, tensile retention, and retrogradation of scCO₂TPS_xPVA^a_y with decreasing PVA's DP are proposed.